When Viruses Jump Cages

 

Ebola Virus - Credit CDC

 

# 6722

 

 

With Uganda’s second outbreak of Ebola Sudan in recent months announced earlier this week, along with their ongoing outbreak of Marburg Hemorrhagic Fever, the news that researchers in Canada have documented the transmission of Ebola Zaire from pigs to monkeys – without direct contact - has captured a good deal of attention this week.

 

This transmission occurred in an artificial laboratory setting, with prolonged-close, but-not-direct-contact, and doesn’t necessarily represent how things happen in the `real world’.

 

Nonetheless, it is notable since the conventional wisdom of how Ebola viruses are spread has long been:

 

People can be exposed to Ebola virus from direct contact with the blood and/or secretions of an infected person. Thus, the virus is often spread through families and friends because they come in close contact with such secretions when caring for infected persons. People can also be exposed to Ebola virus through contact with objects, such as needles, that have been contaminated with infected secretions. – CDC Special Pathogens Branch

 

At this point it is important to note that there is nothing in this new research to suggest that the Ebola virus has suddenly gone `airborne’. 

 

But we’ll get to that a little later. 

 

We’ve known since 2008 that pigs can carry some Ebola viruses (see When Viruses Jump Species), usually without showing ill effects. 

 

First detection of Ebola-Reston virus in pigs

23-12-2008

FAO/OIE/WHO offer assistance to the Philippines

Manila/Roma, 23 December 2008 - Following the detection of the Ebola-Reston virus in pigs in the Philippines, FAO, the World Organization for Animal Health (OIE) and the World Health Organization (WHO) announced today that the government of the Philippines has requested the three agencies send an expert mission to work with human and animal health experts in the Philippines to further investigate the situation.

(Continue . . .)

 

Roughly a month later, we learned that several farm workers in contact with infected pigs tested positive for antibodies to the Ebola-Reston virus.  None displayed any signs of illness.

 

Ebola Reston in pigs and humans in the Philippines

3 February 2009 - On 23 January 2009, the Government of the Philippines announced that a person thought to have come in contact with sick pigs had tested positive for Ebola Reston Virus (ERV) antibodies (IgG). On 30 January 2009 the Government announced that a further four individuals had been found positive for ERV antibodies: two farm workers in Bulacan and one farm worker in Pangasinan - the two farms currently under quarantine in northern Luzon because of ERV infection was found in pigs - and one butcher from a slaughterhouse in Pangasinan. The person announced on 23 January to have tested positive for ERV antibodies is reported to be a backyard pig farmer from Valenzuela City - a neighbourhood within Metro Manila.

(Continue . . .)

Ebola-Reston is the only one of five known Ebola viruses that is not pathogenic in humans.  It can kill simians, and its ability to infect pigs is worrisome given how similar human and porcine immune systems are to each other.

 

The natural reservoir for Ebola viruses are believed to be fruit bats of the Pteropodidae family. While the route of initial transmission to a human host is often undetermined, the assumption is that it is usually linked to the consumption of infected bushmeat (probably an intermediate host).

 

Although Ebola-Reston has been documented in pigs in the Philippines, it isn’t clear what role – if any - pigs play in the ecology of Ebolaviruses virus in Africa.

 

In 2011 researchers showed that pigs were also highly susceptible to Ebola-Zaire, which can be up to 90% fatal in humans. 

 

This from the Journal of Infectious Diseases.

 

 

Replication, Pathogenicity, Shedding, and Transmission of Zaire ebolavirus in Pigs

Gary P. Kobinger, Anders Leung, James Neufeld, Jason S. Richardson, Darryl Falzarano, Greg Smith, Kevin Tierney, Ami Patel and Hana M. Weingartl

 

 

This week’s study, which appears in Scientific Reports, takes this information one step further. Researchers placed four macaques in a wire cage inside a pig pen where pigs, infected with Ebola-Zaire, were kept.

 

Although sharing common living space, they were separated by the wire cage. Yet after 2 weeks of shared confinement, all four macaques had contracted the virus.

 

 

Transmission of Ebola virus from pigs to non-human primates

Hana M. Weingartl,Carissa Embury-Hyatt,Charles Nfon,Anders Leung,Greg Smith& Gary Kobinger

Article number: 811 doi:10.1038/srep00811

 

Abstract (Excerpt)

Here we show ZEBOV transmission from pigs to cynomolgus macaques without direct contact. Interestingly, transmission between macaques in similar housing conditions was never observed. Piglets inoculated oro-nasally with ZEBOV were transferred to the room housing macaques in an open inaccessible cage system. All macaques became infected. Infectious virus was detected in oro-nasal swabs of piglets, and in blood, swabs, and tissues of macaques. This is the first report of experimental interspecies virus transmission, with the macaques also used as a human surrogate. Our finding may influence prevention and control measures during EBOV outbreaks.

 

Researchers speculate that:

 

. . .  transmission of ZEBOV could have occurred either by inhalation (of aerosol or larger droplets), and/or droplet inoculation of eyes and mucosal surfaces and/or by fomites due to droplets generated during the cleaning of the room. Infection of all four macaques in an environment, preventing direct contact between the two species and between the macaques themselves, supports the concept of airborne transmission.

While there is some degree of ambiguity here, the idea that large droplet transmission over a very short distance occurred in this setting is not unreasonable. The researchers conclude by stating (reparagraphed for readability):

The present study provides evidence that infected pigs can efficiently transmit ZEBOV to NHPs in conditions resembling farm setting.

 

Our findings support the hypothesis that airborne transmission may contribute to ZEBOV spread, specifically from pigs to primates, and may need to be considered in assessing transmission from animals to humans in general.

 

The present experimental findings would explain REBOV seropositivity of pig farmers in Philippines that were not involved in slaughtering or had no known contact with contaminated pig tissues.

 

The results of this study also raise a possibility that wild or domestic pigs may be a natural (non-reservoir) host for EBOV participating in the EBOV transmission to other species in sub-Saharan Africa.

 

According to a report by Ed Yong in The Scientist  (see Ebola from Pigs to Monkeys), these researchers are now planning a trip to Africa to do serological testing of pigs in areas that have experienced Ebola outbreaks.

»» Read More

Osterholm: Time To Close The Pig Barns

Credit Wikipedia

 

 

# 6504

 

While the CDC has yet to find evidence of sustained and efficient human-to-human transmission of the emerging H3N2v flu virus, more than 200 human cases reported over the past couple of weeks have made it pretty apparent that this virus jumps readily from pigs to humans.

 

The CDC – citing the lack of H2H transmission and the relative mildness of infections – has advised county fairs and animal exhibits to screen pigs for signs of illness and urge better hygiene among visitors, but has stopped short of recommending the closing of pig barns to the public.

 

Complicating matters, last week we saw a study that showed pigs often carry flu viruses asymptomatically (see EID Journal: Flu In Healthy-Looking Pigs), which makes the advice to identify and isolate sick pigs problematic.

 

This morning, Helen Branswell has a long interview with well known flu expert and CIDRAP  director Michael Osterholm, who believes the time has come to close the pig exhibits at county fairs.

 

Osterholm stresses that we don’t yet know where this virus is going, or how much of a public threat it poses, but that the level of transmission at these venues is sufficient to warrant stronger measures.

 

A link to Helen’s article, then I’ll return with a postscript.

 

August 21, 2012 | 7:00 am

Time to close the pig barns, flu expert says

By Helen Branswell The Canadian Press

TORONTO – It’s been found in pigs and-or people in more than 10 U.S. states and counting. In less than a month, more than 200 people — most young children — have been infected by an unwanted visitor to many of the state and county fairs that are held at this time of year.

 

A new swine flu virus is infecting a growing number of people in the United States. But the official response to this outbreak is substantially different from the one that greeted the swine H1N1 virus that emerged in 2009.

(Continue . . .)

 

 

As I’ve pointed out before, every time this virus jumps from a pig to a human it gets another chance to better adapt to human physiology. Given enough chances, it could evolve into a greater public health threat.

 

So far, we’ve been lucky enough not to have seen a child’s death, or serious illness from this virus.

 

But when we do, you can be sure some aspects of the media a will have a field day excoriating the county fair, local officials, and health department that `let it happen’.

 

Admittedly, the suggestion to close the pig exhibits to the public will not be popular in the farm belt, or among pork producers (who have gone to great lengths to distance themselves from any connection to `swine flu’).

 

But whether the industry likes to admit it or not, pigs are highly susceptible to the influenza virus - and can even serve as `mixing vessels’ - allowing viruses to reassort into new hybrid strains.

 

 

 

The pandemic virus that emerged in the spring of 2009 was the end product of several influenza strains that had kicked around the world’s swine population for many years, trading bits of genetic material back and forth, until they produced a version capable of jumping to humans.

 

The H3N2v virus is likewise a reassortant virus; swine H3N2 combined with the M (matrix) gene from the 2009 H1N1 virus. While the odds of seeing a pandemic emerge from this H3N2v virus appear low right now, they are not zero. 

 

Whatever negative publicity the pork industry might suffer from temporarily shuttering pig exhibits would pale in comparison to the backlash they would see should another swine-origin flu virus take off in a big way in the human population.

 

Nevertheless, the proposal to shutter pig barns is bound to be a sensitive one. It is going to be interesting to see how public health departments, fair officials, and the pork lobby react to Dr. Osterholm’s suggestion in the coming days. 

 

For more on the flu risks from swine reassortments, I’d heartily recommend Helen Branswell’s terrific piece in SciAm  from late 2010 called Flu Factories.

Flu Factories

The next pandemic virus may be circulating on U.S. pig farms, but health officials are struggling to see past the front gate

By Helen Branswell  | December 27, 2010 |

 

 

And for some of my earlier looks at swine influenza, you may wish to revisit:

 

H3N2v: When Pigs Flu

You Say You Want An Evolution?

The (Swine) Influenza Reassortment Puzzle

»» Read More

H3N2v: CDC Offers Advice To Fair Goers

 

Credit Wikipedia

 

# 6455

 

In the wake of this week’s announcement of another fair-related outbreak of H3N2v influenza (see MMWR On The H3N2v Outbreak In LaPorte, Indiana), the CDC has put together a summary of the event and some advice to the fair-going public (and those who raise or come in contact with pigs).

 

 

I’ve only excerpted portions of this lengthy `Flu News’ report, follow the link to read it in its entirety.

 

CDC Reports Cases 14-17 of H3N2v Infection; Shares Advice for Safe Fair-Going

July 27, 2012 -- The state of Indiana this week reported the first novel influenza virus outbreak associated with a fair this season. Following reports of ill swine and humans during a fair in Indiana from July 8-14, samples were taken from swine and humans. Twelve swine were randomly sampled by Indiana state animal health officials, tested at Indiana and federal animal diagnostic laboratories, and found to be infected with swine influenza A (H3N2) viruses. Four people tested positive for influenza A (H3N2) variant virus.* Genetic testing confirmed that the viruses found in humans and those found in swine are nearly identical and both have the M gene from the pandemic H1N1 virus. These cases bring the total number of detected infections with the H3N2v virus containing the pandemic M gene in the United States since 2011 to 17.

<SNIP>

Take Action to Prevent the Spread of Flu Viruses Between People and Pigs**

• Wash your hands frequently with soap and running water before and after exposure to animals.
• Never eat, drink or put things in your mouth in animal areas and don’t take food or drink into animal areas.
• Young children, pregnant women, people 65 and older and people with weakened immune systems should be extra careful around animals.
• If you have animals – including swine – watch them for signs of illness and call a veterinarian if you suspect they might be sick.
• Avoid close contact with animals that look or act ill, when possible.
• Avoid contact with pigs if you are experiencing flu-like symptoms.

If you must come in contact with pigs while you are sick, or if you must come in contact with pigs known or suspected to be infected, or their environment, you should use appropriate protective measures (for example, wear protective clothing, gloves, masks that cover your mouth and nose, and other personal protective equipment) and practice good respiratory and hand hygiene.

Certain People at Higher Risk

“For influenza, certain people may be at higher risk of getting infected, or may be at higher risk for more severe outcomes,” says Jernigan. Studies conducted by CDC have indicated that children younger than 10 would have little to no immunity against H3N2v, whereas adults may have some cross-protective immunity. Most cases of H3N2v have occurred in children at this time. Other people who are at higher risk for seasonal flu-related complications include people with asthma, diabetes, heart disease or neurological disorders. “Prevention is especially important for these people,” says Jernigan.

(Continue . . .)

»» Read More

Branswell: Podcast On Flu Factories

 

 

 

# 5175

 

 

If you were tasked with finding a medical reporter with a better understanding of influenza than Helen Branswell  . . . well, you’d be searching a long, long time.  Ms. Branswell heads a very short list of truly excellent reporters in that field. 

 

Helen is a long time medical correspondent for the  Canadian Press, and is currently a Nieman Fellow for Global Health Reporting at Harvard University.

 

This week, Helen has a feature article that looks at pig farms as incubators of influenza in the January edition of Scientific American, called  Flu Factories. 

 

If you have a subscription (there is a free synopsis), you can read the article online at:

 

Flu Factories

The next pandemic virus may be circulating on U.S. pig farms, but health officials are struggling to see past the front gate

By Helen Branswell  | December 27, 2011 

 

 

I am very happy to report that SciAm also has a freely available 15 minute audio interview with Helen, as well.

 

 

How You Gonna Keep Flu Down on the Farm?: Pig Farms and Public Health

Journalist Helen Branswell discusses her January Scientific American article, "Flu Factories," about the attempts to monitor new strains of flu that can originate on pig farms and the difficulties of balancing economic and public health constituencies.

 

 

Both the article, and the podcast, are highly recommended.

»» Read More

UK: Flu Prevalence In Pigs

 

 

# 4898

 

 

A presentation at the 21st International Pig Veterinary Society (IPVS) Congress held last July in Vancouver, Canada is making a bit of a stir in the farm trade magazines over the past week or so.

 

 

It details the discovery of a higher-than-expected rate of influenza infection among pigs in the UK.

 

The original abstract appears on page 269 the 1229 page Proceedings of the 21s IPVS PDF, which may be downloaded from the IPVS2010 website.

 

 

Towards risk-based surveillance for swine influenza virus

Barbara Wieland, Alexander Mastin, Dirk U. Pfeifer, The COSI Consortium
 

 

Farm publications covering the story include:

 

Swine 'flu more widespread in England than previously realised – Vetsonline

Swine Influenza Widespread in England, France - Thepigsite

Swine influenza widespread in England – FarmingUk

 

 

The researchers enrolled 146 farrow-to-finish farms representing roughly 17% of the English swine herd, and the conducted surveillance by taking serum samples from 20 animals from each farm.

 

Using Hemagglutination Inhibition (HI) assays, they tested for H1N1, H1N2, and H3N2 flu viruses. 

 

They also collected supplementary information on herd management, health, reproduction, and farm environment to help with their analysis.

 

The results showed that 59% of the farms tested turned up at least 1 (out of 20 pigs tested) with an HI titer of 1:40  or 2 pigs with lower titers.  

The most commonly detected virus was an avian-like H1N1, followed by H1N2, and with just one with H3N2.  18% of farms tested positive for two strains – H1N1 and H1N2 – which the authors state could either represent a cross-reaction or infection with both strains.

 

According to the Vetsonline article, the incidence of swine influenza detected in France in 2009 was far higher, with 97% of the 29 farms tested positive for at least one strain of the virus.

 

These strains are consistent with what is normally detected in pig herds, although the prevalence is higher than many had expected in the UK. This from the CDC Factsheet on swine influenza.

 

Key Facts about Swine Influenza (Swine Flu)

Over the years, different variations of swine flu viruses have emerged. At this time, there are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2, and H3N1. However, most of the recently isolated influenza viruses from pigs have been H1N1 viruses.

 

 

H1N2 is assumed to be a reassortment between the H1N1 and H3N2 virus. It has occasionally been detected in humans, and appears to be no more virulent that its parents. 

 

Since its hemagglutinin and neuraminidase proteins are similar to the contributions from H1N1 and H3N2, the seasonal flu vaccine is believed to provide adequate protection.

 

While swine flu infections are often mild or subclinical in pig herds, and may not appear to have much impact, they can adversely affect productivity. Infection can result in abortion, still born piglets, and decreased lactation in sows.

 

Beyond the economics of farm production, there is an even greater reason to try to control swine influenza: the potential of seeing newly emerging viruses from the farm.

 

While influenza viruses normally mutate and change slowly over time time due to antigenic drift, bigger, more abrupt changes come about through a process known as antigenic shift.

 

Shift can occur when a novel virus makes a direct jump from another species to humans or (more likely) a reassortment of two flu viruses occurs in a host animal resulting in a new hybrid virus.

 

While rare, as any virologist will tell you.   Shift Happens.

Although any susceptible host has the potential to serve as a `mixing vessel’ for influenza viruses, pigs appear particularly well adapted for this role. They are capable of being infected by a wide range of human, swine, and avian viruses.

 

Increasingly we are seeing research and surveillance showing how influenza viruses mutate and adapt within the pig host.   A few examples include:

 

When Pigs Flu

EID Journal: Swine Flu Reassortants In Pigs

If You’ve Seen One Triple Reassortant Swine Flu Virus . . .

Hong Kong: Swine Flu Reassortment

H3N2 Swine Flu

 

 

Although avian influenzas had captured the headlines up until a couple of years ago, since the outbreak of pandemic H1N1 in 2009 - which circulated under-the-radar in pigs for about 10 years – scientists are looking at pigs, and swine influenzas with keener interest today.

 

Source: FAO

 

With global pig production growing rapidly to meet the demands of a hungry world, each year we add millions more `mixing vessels’ to natures laboratory. 

 

The prevalence of influenza in UK pigs in the above report is obviously a concern, but it is the lack of surveillance and reporting on swine influenzas from around the world that is particularly worrisome.

 

A blind spot that could allow another novel influenza virus to emerge with virtually no warning, and spark another global pandemic.

»» Read More

When Pigs Flu

 

 

# 4884

 

 

For the second time in a month we’ve a study on reassortant influenza viruses in pigs.  The first one I wrote about in August in a blog called EID Journal: Asymptomatic H5N1 In Pigs and again in earlier this month in A Bold Bird Flu Headline From Japan.

 

This study was also featured in a New Scientist article earlier this week called Bird flu jumps to pigs.

 

To recap briefly:

 

Chairul Nidom of the Institute of Tropical Disease, Airlangga University in Indonesia - along with colleagues in Japan - have been conducting surveillance of Indonesia’s pigs since 2005.

 

They found that between 2005 and 2007, 7.4% of pigs tested asymptomatically carried the H5N1 virus.  Phylogenic analysis showed at least 3 separate introductions into the pig population.

 

Of particularly concern, in one sample researchers found an adaptation of the virus to human-like receptor cells via an Ala134Ser mutation (swaping alanine with serine) at position 134.

 

The study can be viewed in the CDC’s  EID Journal at:

DOI: 10.3201/eid1610.100508

Nidom CA, Takano R, Yamada S, Sakai-Tagawa Y, Daulay S, Aswadi, D, et al. Influenza A (H5N1) viruses from pigs, Indonesia. Emerg Infect Dis. 2010 Oct;[Epub ahead of print]

Influenza A (H5N1) Viruses from Pigs, Indonesia

 

Which brings us now to the second study, this time out of China, that appears in the PLoS One  Journal this week called:

 

Reassortant between Human-Like H3N2 and Avian H5 Subtype Influenza A Viruses in Pigs: A Potential Public Health Risk

Yanlong Cong, Guangmei Wang, Zhenhong Guan, Shuang Chang, Quanpeng Zhang, Guilian Yang, Weili Wang, Qingfeng Meng, Weiming Ren, Chunfeng Wang, Zhuang Ding

 

Essentially what they found was that during the surveillance period between  2007 and 2008 H3N2 influenza viruses were regularly detected from domestic pigs in Jilin Province, China.

 

 

 

Phylogenetic analysis showed two distinct lineages:

 

• One that closely matched the contemporary strain of human-like H3N2 viruses
• And another consisting of double-reassortant viruses containing genes from human H3N2 viruses and avian H5 viruses.

 

It’s a long and informative study (with a lot of technical detail on how it was conducted), but their conclusion reads:

 

Conclusions

The present study reports for the first time the coexistence of wholly human-like H3N2 viruses and double-reassortant viruses that have emerged in pigs in Jilin, China. It provides updated information on the role of pigs in interspecies transmission and genetic reassortment of influenza viruses.

 

As we’ve talked about many times before, pigs have long been believed to be ideal `mixing vessels’ for influenza because they possess both avian-like (SAα2,3Gal) and human-like (SAα2,6Gal) receptor cells in their respiratory tract.

 

That means pigs are susceptible to human, swine, and avian strains of flu.  And they are capable of being infected by more than one flu virus at a time.

 

This raises the possibility that two flu viruses could swap genetic material inside a pig, and create a hybrid (reassortant) strain.  One that could go on to infect humans.

 

 

This is basically how the 2009 H1N1 pandemic virus evolved, although it took multiple gene swaps over a decade or longer before it finally emerged into the human population.

 

We know that reassortments happen, but only rarely do they result in a biologically fit virus capable of causing a pandemic.  Most hybrids are evolutionary dead-ends and die out within the host.

 

Source: FAO

But as global pig production grows to meet the demands of a hungry world we have a rapidly escalating global pig population - playing host to numerous strains of human, swine and avian influenzas – all of which creates increasing opportunities for a new virus to emerge.

 

Crowded factory farming techniques, the transport of live pigs across long distances, and a lack of biosecurity controls and surveillance at many pig farms around the globe all compound the risk.

 

For more insight on these practices, you may wish to view Michael Greger’s eye-opening video Flu Factories.

 

Admittedly, it may be years or even decades before another `swine flu’ emerges and threatens the human population. The timing of these events is impossible to predict.

 

But surveillance studies like the two mentioned above show that nature’s laboratory is vast, open 24/7, and actively engaged in genetic experimentation.

 

Which means that it isn’t a matter of if a new virus will emerge. 

 

It is probably just a matter of when.

»» Read More

A Bold Bird Flu Headline From Japan

 

 

# 4860

 

 

Arkanoid Legent has a story this morning from the Asahi Shimbun in Japan with this attention getting headline:

 

Mutated avian flu can infect humans

BY YURI OIWA THE ASAHI SHIMBUN

A strain of highly pathogenic avian influenza (H5N1) that mutated in pigs in Indonesia has acquired the ability to infect humans, researchers have found.

(Continue . . .)

 

 

If all of this sounds a bit familiar, it may be because I wrote about this study at some length in mid-August (see EID Journal: Asymptomatic H5N1 In Pigs). 

 

While obviously an important piece of field research - one that illustrates why we need to do a much better job of surveillance of pigs (and other mammals) for emerging viruses – the headline and lede may be just a tad overstated.

 

Since this story is likely to get a good deal of play over the next few days, a revisiting of the original study seems in order.

 

First, the setup for the research via some excerpts (slightly reformatted for readability) from the EID Journal abstract . . . then some discussion.

 

DOI: 10.3201/eid1610.100508

Nidom CA, Takano R, Yamada S, Sakai-Tagawa Y, Daulay S, Aswadi, D, et al. Influenza A (H5N1) viruses from pigs, Indonesia. Emerg Infect Dis. 2010 Oct;[Epub ahead of print]

Influenza A (H5N1) Viruses from Pigs, Indonesia

Pigs have long been considered potential intermediate hosts in which avian influenza viruses can adapt to humans. To determine whether this potential exists for pigs in Indonesia, we conducted surveillance during 2005–2009.

 

 

Pigs have long been suspected as being ideal `mixing vessels’ for influenza because they possess both avian-like (SAα2,3Gal) and human-like (SAα2,6Gal) receptor cells in their respiratory tract.

 

That means pigs are susceptible to human, swine, and avian strains of flu.  And they are capable of being infected by more than one flu virus at a time.

 

This opens the possibility for two flu viruses to swap genetic material inside a pig, and create a hybrid (reassortant) strain as depicted in the illustration below (other hosts can cause reassortments, too).

 

 

This is essentially how the 2009 H1N1 pandemic virus was born, although it took multiple gene swaps over a period of years before it emerged into the human population.

 

The highlights of this latest study were:

 

Researchers found that during the period of 2005-2007 that 7.4% of pigs surveyed in Indonesia carried the H5N1 virus.

 

Phylogenic analysis showed at least 3 separate introductions into the pig population.

 

More recent surveillance (2008-2009) did not turn up any active infections, but 1% of pigs tested carried antibodies to the H5N1 virus.

 

The pigs were asymptomatic, but the evidence points to ongoing transmission within the pig population.

 

In one sample researchers found an adaptation of the virus to human-like receptor cells via an Ala134Ser mutation (swaping alanine with serine) at position 134.

 

The last point is obviously a concern.

 

But just as obviously, if only one instance was detected – and that was at least 3 years ago – then that particular mutation isn’t exactly thriving in Indonesia’s pig population.

 

The point is . . .  if it happened once, it could obviously happen again. 

 

And the next time, the reassorted virus could be more biologically `fit’, and start efficiently spreading to other pigs, and eventually perhaps to humans. 

 

Which is why surveillance of farm animals (particularly, but not exclusively, pigs) is so important. 

 

And not just in Indonesia.

Despite the danger posed by emerging viruses there is considerable reluctance to testing herds of swine, both here in the US, and around the world.  

 

Pig owners fear negative publicity, or a culling of their herds, should anything be found. And of course, surveillance costs money.

 

`Swine flu’ proved to be an expensive public relations nightmare for the pork industry, and so pig farmers are understandably wary.

 

 
As the authors point out, the asymptomatic carrying of these viruses is of particular concern.  There are no outward signs to alert a farmer than their herd is sick.

 

This could lead to infected pigs being transported to new areas, or intermingled with uninfected swine, spreading a new virus further. 

 

The important point to this story is not so much the one human-adapted virus they discovered in 2007, but what we need to be looking for today.  

 

And in far too many places around the world, simply are not.

»» Read More

EID Journal: Asymptomatic H5N1 In Pigs

 

 

# 4803

 

 

Today an important study in the CDC’s EID Journal, epublished ahead of its scheduled October printing, that looks at the infiltration of H5N1 (bird flu) into Indonesia’s pig population.

 

The authors list reads like a `who’s who’ of influenza research – many being familiar to readers of this blog - including such names as C. A. Nidom and Yoshihiro Kawaoka.

 

First some excerpts (slightly reformatted for readability) from the abstract . . . then some discussion.

 

DOI: 10.3201/eid1610.100508
Nidom CA, Takano R, Yamada S, Sakai-Tagawa Y, Daulay S, Aswadi, D, et al. Influenza A (H5N1) viruses from pigs, Indonesia. Emerg Infect Dis. 2010 Oct;[Epub ahead of print]

Influenza A (H5N1) Viruses from Pigs, Indonesia

 

Pigs have long been considered potential intermediate hosts in which avian influenza viruses can adapt to humans. To determine whether this potential exists for pigs in Indonesia, we conducted surveillance during 2005–2009.

 

We found that 52 pigs in 4 provinces were infected during 2005–2007 but not 2008–2009.

 

Phylogenetic analysis showed that the viruses had been introduced into the pig population in Indonesia on at least 3 occasions. One isolate had acquired the ability to recognize a human-type receptor.

 

No infected pig had influenza-like symptoms, indicating that influenza A (H5N1) viruses can replicate undetected for prolonged periods, facilitating avian virus adaptation to mammalian hosts.

 

Our data suggest that pigs are at risk for infection during outbreaks of influenza virus A (H5N1) and can serve as intermediate hosts in which this avian virus can adapt to mammals.

 

 

Pigs have long been suspected as being ideal `mixing vessels’ for influenza because they are believed susceptible to a wide variety of human, swine, and avian flu viruses.

 

Swine possess both avian-like (SAα2,3Gal) and human-like (SAα2,6Gal) receptor cells in their respiratory tract, which scientists believe can facilitate a `bridging’ between avian and human strains.

 

The recent emergence of the 2009 H1N1 virus, after reassorting and bouncing around in pigs for years, has helped reinforce that theory.

 

But whether the H5N1 bird flu strain can readily adapt to, infect, and transmit among pigs has been an open question. 

 

In previous experiments, domestic pigs were demonstrated to have low susceptibility to the H5N1 virus, producing asymptomatic to mildly symptomatic infection of the respiratory tract and tonsils. 

 

Viral titers were lower than normally seen with swine influenzas, suggesting a limited ability to adapt and spread among pigs.

 

Today’s research found that during the period of 2005-2007 that 7.4% of pigs surveyed in Indonesia carried the H5N1 virus, and that phylogenic analysis showed at least 3 separate introductions into the pig population.

 

More recent surveillance, during 2008-2009 did not turn up any active infections, but 1% of pigs tested carried antibodies to the H5N1 virus.

 

The pigs (as in the study mentioned above) were asymptomatic, but the prevalence among pigs and genetic similarities among isolates were viewed as evidence of ongoing transmission within the pig population.

 

In at least one sample, the researchers found evidence of an adaptation of the virus to human-like receptor cells with via an Ala134Ser mutation (substitution of alanine with serine) at position 134.

 

While the entire study is of interest, and very much worth reading, a few notable quotes to whet your curiosity:

 

• These findings show that although influenza A (H5N1) viruses may not have been extensively circulating in pigs in Indonesia recently, these animals are susceptible to influenza A (H5N1) viruses and can serve as asymptomatic reservoirs for these viruses.

• We conclude that the 3 groups of viruses identified in this survey were likely established independently, suggesting at least 3 separate avian-to-pig episodes of transmission of influenza A (H5N1) viruses during 2005–2009 in Indonesia.

• . . . when an outbreak of influenza A virus (H5N1) infection occurs on poultry farms, pigs on nearby farms should be evaluated for infection

• We also found evidence of pig-to-pig transmission of influenza A virus (H5N1), particularly among animals sampled during the first surveillance period.

• The lack of influenza-like signs in pigs infected with influenza A (H5N1) viruses has several public health implications.

• In Indonesia, pigs are transported to different locations according to market needs. This movement is reflected in our finding that clusters of swine viruses collected after 2006 were not consistent with those common to the sampling region.

• Indeed, viruses collected in North Sumatra, South Kalimantan, East Java, and Banten provinces showed identical or nearly identical genes, indicative of extensive transport of infected pigs throughout Indonesia.

• Thus, pathogenic influenza A (H5N1) viruses could easily evade detection as they spread through Indonesia in asymptomatic pigs being transported from province to province.

»» Read More

Hong Kong: More Pigs Test Positive For H1N1

 

 

 

# 4200

 

 

Were it not for concerns over the potential for the pandemic H1N1 virus to acquire additional genetic changes via reassortment, the discovery of the virus in swine would be a non-story by now.

 

After all, as a swine-origin influenza virus, novel H1N1 is understandably pretty comfortable in a swine host.

 

Just yesterday we saw a report of a 16th pig farm in South Korea reporting the infection.  In recent months farms in Europe, North and South America, and Asia have all reported livestock infections.  

 

Pigs are susceptible to a variety of human, avian, and swine influenza viruses.  They can even be infected by two different flu viruses at the same time.  

 

As such, they are considered to be good `mixing vessels’ for viruses, and could help produce a hybrid `reassorted’ virus.  One that could potentially have pandemic potential.

 

 

Of course, that’s a pretty rare occurrence.  

 

You not only need two compatible flu viruses to inhabit the same cell at the same time, it needs to produce a `fit’ hybrid.  One that replicates well, is adapted to human receptor cells, and is easily transmitted.

 

It appears that our 2009 pandemic virus bounced around in pigs for many years, picking up multiple mutations (via reassortment), before it found the right combination to jump to humans.

 

It could take years, perhaps decades, before we see that sort of thing happen again.  

 

Or it could happen tomorrow.

 

The infected swine detected in this report from Hong Kong came from the Chinese mainland where little or no testing occurs, and bio security on farms often leaves much to be desired.

 

Other influenza viruses, including the H5 and H9 avian viruses, are also known to circulate among domesticated livestock in that region, and that has some scientists concerned.

 

The good news here is that testing so far has shown no gene reassortment to have occurred, and the virus detected remains genetically similar to the H1N1 pandemic virus.

 

This from News.gov.hk.

 

 

 

 

 

Pigs test positive for human swine flu

December 30, 2009

The University of Hong Kong's influenza virus surveillance programme found five samples taken from pigs at the Sheung Shui Slaughterhouse on December 17 tested positive for the human swine influenza virus, the Food & Environmental Hygiene Department said today.

 

This is the third time the programme uncovered positive samples. No gene reassortment has occurred and the virus remained genetically similar to the human swine flu viruses regularly found in people. The flu virus is believed to have been transmitted from people to pigs.

 

The concerned samples were taken from pigs imported from the Mainland. The department informed the Mainland authorities, and they have strengthened monitoring of registered farms that supply live pigs to Hong Kong.

 

The World Health Organisation, World Organisation for Animal Health, Food & Agriculture Organisation of the United Nations and World Trade Organisation state that pork and pork products which are handled properly and thoroughly cooked are not a source of human swine flu infection.

(Continue . . .)

 

»» Read More

WHO Pandemic Briefing #15: Farmed Animals And H1N1

 

# 3959

 

The World Health Organization has released their 15th Pandemic Briefing note, this time dealing with the hot subject of the H1N1 virus beginning to show up in farm animals, such as turkeys and pigs.

 

This has been a frequent topic of conversation in this, an many other flu blogs, with my latest blog about this coming earlier today.

 

 

 

Infection of farmed animals with the pandemic virus

Pandemic (H1N1) 2009 briefing note 15

5 NOVEMBER 2009 | GENEVA -- To date, extensive testing by laboratories in the WHO influenza surveillance network has detected no signs that the H1N1 pandemic virus has mutated to a more virulent form. Currently licensed pandemic vaccines closely match circulating viruses and are expected to confer good protection.

 

Vigilance for changes in the H1N1 virus includes monitoring to detect possible influenza infections in susceptible animals, both mammals and birds, as well as humans. While most influenza A viruses circulating in mammals preferentially infect a single species, cross-species transmission is known to occur.

Infections in swine

Concern has traditionally focused on swine, which are susceptible to infections from human and avian influenza viruses as well as swine influenza viruses. As influenza viruses have eight neatly segmented genes, swine could theoretically operate as a viral “mixing vessel” for the exchange of genetic material when an animal is co-infected with different viruses. Such an event could lead to changes in the genetic makeup of the H1N1 virus or result in a novel influenza virus of unknown public health significance.

 

Since the new H1N1 pandemic virus emerged, a small number of infections in swine herds have been reported. Limited evidence suggests that these infections occurred following direct transmission of the virus from infected humans to swine. These isolated events have had no impact on the dynamics of the pandemic, which is spreading readily via human-to-human transmission. As human infections become increasingly widespread, transmission of the virus from humans to swine is likely to occur with greater frequency.

Influenza in other species

In addition, pandemic H1N1 infections have been reported in turkeys in Chile and Canada and in a few pet animals in the USA. Again, these infections were isolated events and pose no special risks to human health.

 

The virus is killed at normal cooking temperatures. No human infections have been linked to the consumption of properly prepared meat or animal products, or any other food items.

 

Another concern is the continuing presence of the highly pathogenic H5N1 avian influenza virus in poultry in several countries, where the virus is endemic. While no one can predict how the H5N1 virus might behave under the pressures of a pandemic, all data to date have been reassuring.

 

Most recently, authorities in Denmark reported a novel H3N2 influenza virus in mink on several mink farms. Sequencing of the virus demonstrated a combination of human and swine genes that has not been identified previously in circulating influenza viruses. Testing of farm workers detected no spread of the virus to humans. However, the incident demonstrates the constantly evolving ecology of influenza viruses, the potential for surprising changes, and the need for constant vigilance, also in animals.

Close monitoring needed

These recent findings further suggest that influenza A viruses in animals and humans increasingly behave like a pool of genes circulating among multiple hosts, and that the potential exists for novel influenza viruses to be generated in animals other than swine. This situation reinforces the need for close monitoring and close collaboration between public health and veterinary authorities.

 

When influenza infections are detected in farmed animals, WHO recommends monitoring of farm workers for signs of respiratory illness, and testing for H1N1 infection should such signs appear. FAO and OIE recommend that animals that are showing signs of illness be examined and properly managed, and allowed to fully recover before being transported or marketed.

 

In addition, samples from infected animals and humans should be taken for full genome sequencing of the influenza viruses to determine if mutations have occurred that could lead to changes in virulence, host range or antiviral resistance. Such sequencing is also important to assess the possible origin of the case or outbreak.

Official notification

Highly pathogenic avian influenza virus infections in birds must be reported to the World Organisation for Animal Health (OIE), as must any "emerging disease" in animals. This would include infections with the pandemic H1N1 virus or other novel influenza viruses, when consistent with the “emerging disease” criteria for official notification.

 

These animal health events should be reported, together with the results of epidemiological and virological investigations, in keeping with OIE requirements for notification.

RELATED LINKS

Evolution of pandemic H1N1 2009 in animals
Press release from the World Organisation for Animal Health (OIE)

Food and Agriculture Organization of the United Nations (FAO): Pandemic (H1N1) 2009

»» Read More

Hong Kong Finds H1N1 In Pork Samples

 

 

# 3957

 

 

We can add Hong Kong to the growing list of countries where the novel H1N1 virus has been detected in pigs.  This time, however, the virus was found in pork samples taken at a slaughterhouse – not in a living pig.

 

The press release below, from the Hong Kong government, stresses the safety of consuming fully cooked pork products – a point that the pork industry would like to see emphasized.  

 

And while that would appear to be true, that isn’t our primary concern when it comes to infected pigs.   But  more on that in a minute. 

 

First, the press release (hat tip Ironorehopper on FluTrackers).

 

 

Pig samples test positive for human swine influenza virus

 

Thursday, November 5, 2009
Issued at HKT 16:13

 

The University of Hong Kong (HKU) had found in its regular influenza virus surveillance programme that two pig samples taken at the Sheung Shui Slaughterhouse on October 22 tested positive for human swine influenza (pandemic influenza A H1N1) virus, a spokesman for the Food and Health Bureau said today (November 5).

 
This surveillance programme has been ongoing since 1999 and this is the first time that the human swine flu virus has been detected in pigs in this surveillance.  No gene reassortment has occurred and the virus remains genetically similar to the human swine flu viruses regularly being found in humans.

 

Experts in charge of the surveillance programme considered that these findings indicate that the human swine flu virus detected in pigs is recently transmitted from humans to pigs.  The risk of humans contracting human swine influenza virus has not increased.

"The findings echo similar reports in other countries," the spokesman said.

"There is no cause for the public to be overly concerned.  Human swine flu virus is killed under a temperature of 70 degree Celsius or above.  It is safe for the public to eat pork and pork products that are handled properly and cooked thoroughly."

 

He pointed out that the World Health Organisation, World Organisation for Animal Health, Food and Agriculture Organisation of the United Nations and World Trade Organisation had already stated that pork and pork products which were handled properly and thoroughly cooked were not a source of human swine influenza infection.

(Continue . . . )

 

Despite the constant bland assurances over the safety of consuming pork, the real concern is that pigs are excellent mixing vessels for influenza viruses, and that a new `reassorted’ virus could emerge and become a human health threat.

 

Of course, that’s a pretty rare event. After all, nothing like that has happened since . . . last spring.

 

The list of countries detecting the novel H1N1 virus among swine  continues to increase with Canada, the US, Japan, Ireland, Norway, Australia, Argentina, Iceland, and now China reporting infections.

 

Many countries either aren’t testing, or do so in a limited fashion, and so this list is likely incomplete.

 

A couple of weeks ago, David Brown of the Washington Post had an excellent report on the rising concerns over infections among swine herds.

 

Back where virus started, new scrutiny of pig farming

By David Brown

Washington Post Staff Writer
Sunday, October 25, 2009

 

And you’ll find a few of my recent blogs on the subject below.

 

Swine Flu: Don’t Test, Don’t Tell

Japan Testing Swine For Suspected H1N1

Referral: Effect Measure On Human Swine Flu In Pigs

Norway: Swine Flu Infects 14 Farms

»» Read More

Iceland: Pigs Test Positive For Novel H1N1

 

# 3897

 

 

The list of countries detecting the novel H1N1 virus among swine  continues to increase with Canada, the US, Japan, Ireland, Norway, Australia, Argentina and now Iceland reporting infections.

 

Many countries either aren’t testing, or do so in a limited fashion, and so this list is likely incomplete.

 

A hat tip to Crof at Crofsblog for this link, and to Dutchy and Hogweed on FluTrackers, who has been translating and posting articles in this thread since yesterday afternoon on this story. 

 

 

27/10/2009 | 14:00

Pigs in Iceland Catch Swine Flu

 

Pigs from the pork farm Minni-Vatnsleysa in Iceland have been infected by the H1N1 swine flu virus, as confirmed by the University of Iceland’s Institute for Experimental Pathology at Keldur.

 

The Icelandic Food and Veterinary Authority reported on the infection this morning.

 

As soon as suspicion of the infection arose yesterday, limitations were placed on the transport of live animals from the farm and all precautions tightened.

 

Farmers at other pork farms are asked to be alert and report on possible symptoms of swine flu to the local veterinarian as soon as they notice them.

The Icelandic Food and Veterinary Authority emphasizes that swine flu is not carried with food products and that people are not at risk of being infected by eating pork.

 

Over this past weekend David Brown of the Washington Post had an excellent report on the rising concerns over infections among swine herds.

 

Back where virus started, new scrutiny of pig farming

By David Brown

Washington Post Staff Writer
Sunday, October 25, 2009

 

And you’ll find a number of my recent blog entries have focused on the spreading of H1N1 among swine.

 

Swine Flu: Don’t Test, Don’t Tell

Japan Testing Swine For Suspected H1N1

Referral: Effect Measure On Human Swine Flu In Pigs

Norway: Swine Flu Infects 14 Farms

»» Read More

Japan Testing Swine For Suspected H1N1

 

 

# 3861

 

 

Despite the protestations of pork producers around the world, the novel H1N1 virus is a `swine flu’ virus, and to little surprise, is now increasingly being found in herds around the globe.

 

Last May, after the discovery of the H1N1 virus in pigs in Alberta, the FAO (The UN’s Food & Agriculture Organization) strongly urged that increased surveillance of the world’s commercial swine herds take place.

 

Canada pig flu case shows need for surveillance: FAO

By Silvia Aloisi, Reuters May 3, 2009 9:01 AM

ROME -- The transmission of the new H1N1 virus from a man to a herd of swine in Canada is a reason for concern and confirms the need for increased surveillance of pig farms, the United Nations food agency said on Sunday.

 

The response has been less than overwhelming, with some reports here in the US that pork producers are doing less testing, fearing what they might find.

 

Fear over H1N1 detection brings down swine disease samples

Sep 25, 2009
DVM NEWSMAGAZINE

National Report -- The U.S. Department of Agriculture (USDA), concerned about a perceived drop in swine disease samples from pork producers, is urging veterinarians to continue monitoring herds for a variety of diseases, including the H1N1 influenza virus.

 

We’ve been watching a large, multi-farm outbreak among pigs in Norway this week, along with  reports out of the US, Australia, Argentina, and Ireland in recent months.  

 

It is increasingly looking like, if you look for it . . . you’ll find it.

 

How much infection is spreading `under the radar’, in areas that aren’t testing, is impossible to know.

 

Today Japan is investigating  a possible outbreak among pigs in Osaka.   

 

The concern is that pigs are considered excellent mixing vessels for viruses, and that a new `reassorted’ virus could emerge and become a human health threat.

 

Of course, that’s a pretty rare event.  Why, nothing like that has happened since . . . last spring.

 

The latest, from Bloomberg, indicates that the pigs have tested positive for H1N1, but that further genetic tests are  underway.

 

 

Japan Confirms First Case of Swine Flu in Pigs at Osaka Farm

 

By Kanoko Matsuyama

Oct. 21 (Bloomberg) -- Pigs in Osaka Prefecture have contracted swine flu, the first case of the H1N1 virus being detected in Japanese livestock.

 

Operators of the farm in the western prefecture were advised to refrain from moving the pigs until the genetic tests are complete, the Ministry of Agriculture, Forestry and Fisheries said today in a statement on its Web site.

 

The U.K., Norway, Ireland, Argentina, Canada and Australia have reported cases of the H1N1 virus in domestic hog herds, according to the Paris-based World Organization for Animal Health. The U.S. Department of Agriculture this week confirmed H1N1 in a pig in Minnesota, and the virus also has been found in turkeys in Chile.

»» Read More

Referral: Effect Measure On Human Swine Flu In Pigs

 

 

# 3856

 

 

Yesterday, two of the big stories were the confirmation of finding the H1N1 virus in a pig in Minnesota, and the spread of the H1N1 virus among 14 hog farms in Norway.  

 

As I pointed out yesterday, one of the concerns is that the virus could `reassort’ with other flu viruses yielding a new, or mutated virus.

 

Yesterday’s USDA announcement seemed more concerned, however, with reassuring the public that pork was safe to eat.

 

Today the Reveres at Effect Measure discuss the possible public health implications of the H1N1 virus (or any flu virus) spreading through swine herds.

 

Read:

 

Human swine flu in pigs

»» Read More

USDA Confirms H1N1 In Minnesota Pig

 

 

# 3852

 

 

Not unexpectedly, test results have come back on at least one of the 3 pigs from a Minnesota fair in late August showing the H1N1 virus.

 

Below is today’s USDA press release, announcing the test results. The main message here appears to be one of reassurance over the safety of pork and damage control for the battered pork industry.

 

Release No. 0514.09
Contact:
Angela Harless (202) 720-4623

USDA CONFIRMS 2009 PANDEMIC H1N1 INFLUENZA VIRUS PRESENT IN MINNESOTA FAIR PIG SAMPLE

 

Agriculture Secretary Vilsack: "U.S. Pork Is Safe to Eat"

WASHINGTON, Oct. 19, 2009 - Agriculture Secretary Tom Vilsack today announced that USDA's National Veterinary Services Laboratories (NVSL) has confirmed the presence of 2009 pandemic H1N1 influenza virus in a pig sample collected at the Minnesota State Fair submitted by the University of Minnesota. Additional samples are being tested.

 

"We have fully engaged our trading partners to remind them that several international organizations, including the World Organization for Animal Health, have advised that there is no scientific basis to restrict trade in pork and pork products," said Vilsack. "People cannot get this flu from eating pork or pork products. Pork is safe to eat."

 

Sequence results on the hemagglutinin, neuraminidase and matrix genes from the virus isolate are compatible with reported 2009 pandemic H1N1 sequences. The samples collected at the 2009 Minnesota State Fair were part of a University of Iowa and University of Minnesota cooperative agreement research project funded by the U.S. Centers for Disease Control and Prevention which documents influenza viruses where humans and pigs interact at such as fairs.

 

The infection of the fair pig does not suggest infection of commercial herds because show pigs and commercially raised pigs are in separate segments of the swine industry that do not typically interchange personnel or animal stock. USDA continues to remind U.S. swine producers about the need for good hygiene, biosecurity and other practices that will prevent the introduction and spread of influenza viruses in their herd and encourage them to participate in USDA's swine influenza virus surveillance program.

 

More information about USDA's 2009 pandemic H1N1 efforts is available at www.usda.gov/H1N1flu.

 

 

According to the USDA on Friday, samples were taken in late August by a joint project of the University of Iowa and University of Minnesota  in a research project funded by the CDC which documents influenza viruses where humans and pigs come in contact with each other, such as fairs.

 

Recent media reports suggest a growing reluctance on the part of pork producers to test their herds, fearing bad news would further depress pork prices.  

 

This from DMV magazine late last month:

 

Fear over H1N1 detection brings down swine disease samples

Sep 25, 2009
DVM NEWSMAGAZINE

 

National Report -- The U.S. Department of Agriculture (USDA), concerned about a perceived drop in swine disease samples from pork producers, is urging veterinarians to continue monitoring herds for a variety of diseases, including the H1N1 influenza virus.

(Continue)

»» Read More

Norway: Swine Flu Infects 14 Farms

 

 

# 3850

 

 

While we awaits tests on 3 pigs suspected of having had the H1N1 virus in Minnesota, Norway is now reporting that at least 14 pig farms have tested positive for the swine flu virus.

Dutchy over on FluTrackers, along with Anty, Treyfish, and several other newshounds have been tracking, and translating news articles on this emerging story for more than a week.  

 

You can read the history, and follow the future progress here.

 

Early in the outbreak, when it appeared to be localized to only 1 or 2 farms, there were attempts to slaughter infected herds to prevent further spread of the virus.  With the ongoing spread, culling has been abandoned.

 

This latest report was posted and translated by Dutchy.

 

 

Monday 19th October 2009,
Norwegian pigs infected with H1N1
By Ritzau Ritzau@mja.dk

Sick people infect pigs with H1N1 influenza in Norway, where 14 farms are now suffering from the dreaded virus.

 
Sick people infect pigs with H1N1 influenza in Norway, where 14 farms are now suffering from the dreaded virus.

Several pig herds in Norway are infected with H1N1 influenza, also known as swine flu.

It informs the Norwegian food agency, Mattilsynet.

Previously, the infection was limited to North-Trøndelag, which is an area in central Norway. But now there is also found sick pigs in two herds further south in Buskerud and Rogaland.

In total there are proven influenza infection in 14 herds, and took 34 samples.

- It is not surprising that we find infected herds in other parts of the country, said supervisory director in Mattilsynet, Kristina Landsverk.
It is humans, which infects pigs, and Mattilsynet think it may be difficult to restrict the disease, when people across the country are infected with H1N1.

Inspectorate notes that the disease can not be fought with slaughter of pigs and establishment of control zones.

 

 

Overnight ProMed Mail  sent out an update on the H1N1 outbreak among swine in Norway, with excerpts from news reports and this summation:

 

[Norway reported to the OIE, so far, 3 H1N1 outbreaks on pig farms.
The initial, immediate notification was submitted on 12 Oct 2009; follow-up reports were submitted on 13 and 16 Oct 2009; all 3, including a map, are available at

<http://www.oie.int/wahis/public.php?page=event_summary&reportid=8515>.

The most recent follow-up report, number 2, submitted on 16 Oct 2009, included the following epidemiological comments:

“More herds in the district are infected though not all of them have been tested and confirmed as having the pandemic influenza A (H1N1) 2009 variant. No animal contact between this herd and the 2 first confirmed cases. The virus seems to be extremely contagious between humans and pigs. On 15 October, we decided to abandon our attempt at culling infected herds."

 

(continue . . .)

 

 

 

The underlying concern, of course, is that swine are susceptible to a wide variety of influenza viruses, and are thought to make excellent `mixing vessels’ for influenza stains.

 

 

Although the odds of it happening are probably very low, the worry is that a pig could be infected by two different influenza strains simultaneous, and a mixing – or reassortment – of the viruses could take place.   

 

The result could be a new, or mutated, flu virus.  

 

While reassortments do happen - ending up with a biologically `fit’ virus well enough adapted to humans to spread easily - is a pretty rare event.   

 

The novel H1N1 virus we are now dealing with undoubtedly came about through a series of such reassortments, but it also circulated (and mutated) in pigs for years before making that successful jump to humans.

 

Meanwhile, some hog farmers here in the US are reportedly reluctant to test their herds (see Swine Flu: Don’t Test, Don’t Tell) out of fears that the discovery of swine flu would further depress pork sales.

»» Read More