Iowa DPH Reports 3 Novel trH3N2 Cases

 

Note: This story is updated at  More Details On The trH3N2 Story

 

# 5973

 

Reassortant H3N2 virus detected in Pennsylvania,Indiana & Maine – Source CDC

The Iowa Department of Public Health announced today in a brief press release that they have detected three cases of a novel trH3N2 SOIV (Swine Origin Influenza Virus) described as being similar to the ones reported recently in Indiana, Pennsylvania, and Maine.

 

For more on those earlier cases see:

 

CDC Update On trH3N2 Swine Infections

Maine Confirms A 2nd trH3N2 Case

CDC Update On trH3N2 Cases

A 5th trH3N2 SOIV Report

CDC Update On Recent Novel Swine Flu Cases

MMWR: Swine-Origin Influenza A (H3N2) Virus Infection in Two Children

 

Unlike the majority of cases reported over the past few months, these three cases report no animal exposure, and so limited Human-to-Human spread is suspected.

 

My thanks to Carol@SC on the Flu Wiki for posting a news item that led me on a search to find this news release from the Iowa DPH.

 

 

Flu Activity in Iowa Includes Novel Strain

Posted: Tue, 22 Nov 2011 15:09 CST

Important to cover your cough and stay home when sick

Routine surveillance by the Iowa Department of Public Health (IDPH), the State Hygienic Lab and other partners across the state indicate that a novel strain of the influenza virus has been detected in three children in Webster and Hamilton Counties.

This virus, an influenza A/H3N2 recombinant virus, has also been detected in other states in recent months. Symptoms are similar to the regular seasonal flu and include fever, cough, tiredness, body aches and loss of appetite.This influenza A/H3N2 virus contains components of human, avian, H1N1, and swine influenza.

All spread has been human to human, and spread appears to be limited; no further cases have been identified in the last week. None of the cases have had any animal exposure. Because the virus is unique, IDPH has increased surveillance for this strain at clinics and emergency rooms.

 

“It appears the seasonal influenza vaccine currently available may offer some protection against this novel strain,” said IDPH Medical Director, Dr. Patricia Quinlisk. “However, we continue to stress the importance of personal protective actions. Remember the three Cs: Clean you hands frequently; Cover your coughs and sneezes; and Contain germs by staying home when ill.”

 

No serious illness or death has been reported in connection with this novel influenza A/H3N2 virus, and all cases have recovered. For more information on the virus, visit www.idph.state.ia.us/Cade/Influenza.aspx?pg=FluHome .

 

While unusual, human infections by novel swine viruses are not unheard of.  Over the past 5 years more than 2 dozen (trH1N1 & trH3N2) cases have been detected.  Most are a result of direct exposure to swine, although limited human-to-human transmission appears to have occurred.

 

Since these novel H3N2 infections continue to appear in low levels across the upper Midwest,this is obviously a story we will continue to follow.

»» Read More

MMWR Reports 8th trH3N2 Case Of 2011

* * * UPDATED * * *

 

Source – CDC

 

# 5954

While no details have been released yet (we’ll probably get something in tomorrow’s FluView ), today’s MMWR from the CDC lists an 8th trH3N2 human infection, once again from the state of Maine.

 

 

This makes the third case from Maine (or possibly not . . .see the update below), which - along with 3 others in Pennsylvania, and 2 out of Indiana – have been detected since late summer.

 

UPDATE: Based on comments offered by Alert on FluTrackers,  I’m now not certain whether this 8th case reported in today’s MMWR represents a 3rd case in Maine, or is simply a delayed reporting of the 2nd case from late October.

 

We’ll need to wait for clarification from the CDC in order to know for sure.  In any event . . .

 

Triple Reassortant (tr) influenza viruses contain genetic material from avian, swine, and human flu strains. In the case of the 7 reported over the past few months, the H3N2 swine virus has recently picked up the M gene segment from the 2009 H1N1 pandemic virus.

 

We’ll have to wait for confirmation from the CDC as to whether this latest trH3N2 virus matches the earlier isolates genetically (again, see the update above)

 

Epidemiological investigations are ongoing in all three states, and so far it appears that most of the cases have had recent opportunities for exposure to pigs. However, the exact route of transmission has not been firmly established.

 

For some background on all of this, the CDC updated their Swine Flu In Humans webpage three days ago:

 

 

Reported Human Infections with Swine Origin Influenza Viruses (SOIV) in the United States since 2005

As of October 31, 2011, 28 cases of human infection with swine origin influenza viruses have been reported in the United States. These are viruses that normally infect pigs. Like human influenza viruses, there are different subtypes and strains of swine-origin influenza viruses. The main swine influenza viruses circulating in U.S. pigs in recent years are swine triple reassortant (tr) H1N1 influenza virus, trH3N2 virus and trH1N2 virus.

 

Of the 28 human cases reported since 2005, 12 have been trH1N1 viruses, 15 have been trH3N2 viruses and one has been a trH1N2 virus. All 28 persons infected with swine viruses recovered from their illness. Twenty cases occurred in children (persons 18 or younger) and 8 cases occurred in adults. In 24 cases, direct or indirect exposure to swine prior to onset of illness has been identified.

 

Likely transmission of swine-origin influenza virus from close contact with an infected person has been observed in investigations of human infections with swine-origin influenza A virus, but has not resulted in sustained human-to-human transmission.

 

 

The concern here is that given enough opportunities, this virus might evolve into a more human-adapted virus. 

 

Over the past couple of decades we’ve seen a small number of avian, swine, and triple reassortant viruses sporadically jumping from the barnyard to infect humans – but only one has managed to spark a pandemic.

 

Given limited testing and surveillance around the globe, how often these sorts of human infections really happen is unknown. But it is probably safe to assume we only learn about a fraction of them.

 

Like the H5N1, H9N2, H7N7, and other swine and avian flu strains, we watch these sporadic human trH3N2 infections with considerable interest  - not because of the public health threat they pose today - but because of the threat they may potentially pose tomorrow.

 

Earlier blogs on these emerging triple reassortant viruses include:

 

CDC Update On trH3N2 Swine Infections

Maine Confirms A 2nd trH3N2 Case

CDC Update On trH3N2 Cases

A 5th trH3N2 SOIV Report

CDC Update On Recent Novel Swine Flu Cases

MMWR: Swine-Origin Influenza A (H3N2) Virus Infection in Two Children

»» Read More

A 5th trH3N2 SOIV Report

 

 

Reassortant H3N2 virus detected in Pennsylvania & Indiana – Source CDC

# 5913

 

 

My thanks to  Giuseppe Michieli and Missouri Watcher  on FluTrackers for the links to the State of Maine HAN Advisory (2011PHADV018), and weekly influenza surveillance report describing  the recent detection of a novel Swine Origin Influenza Virus (SOIV) in that state.

This is the fifth such virus detection from across the country over the past 3 months, with 3 previous cases reported in Pennsylvania and 1 in Indiana (see CDC Update On Recent Novel Swine Flu Cases).

 

In all 5 of these cases, the virus has been a swine H3N2 virus with the M segment gene borrowed from the 2009 H1N1 virus.

 

From the Weekly Flu Surveillance report:

 

*Novel Influenza A Virus

•  HETL detected a case of influenza A virus that was inconclusive during subtyping.  On October 17
Federal CDC confirmed this isolate to be the 5th recognized case of human infection with S-OtrH3N2
with the M segment gene from the pH1N1virus (also identified in one case in Indiana and three cases in
Pennsylvania).  Investigation is ongoing. 

More information can be found in a Health Alert, released 10/19/2011 accessible through:  http://www.maine.gov/tools/whatsnew/attach.php?id=313425&an=1. 

 

 

The MAINE HAN Message provides the following details:

(EXCERPT)

 

This child became ill in early October 2011 with symptoms similar to seasonal influenza including fever,
cough, headache, sore throat and myalgia.  Prior to illness, the child had exposure to swine including time
spent in a closed setting at an agricultural fair.  Maine CDC and the Department of Agriculture are currently investigating exposures. Presently this is an isolated event and Maine CDC has not confirmed any person to person transmission.  

Recommendations:  Maine CDC recommends the following for healthcare providers:

 
•  Maintain a heightened awareness for influenza-like illness (ILI) defined as fever greater than 100° with cough or sore throat, in the absence of another known cause.

• Consider influenza testing by PCR for: 
  patients with ILI with recent exposure to pigs.
• patients with ILI who are hospitalized, 
• patients with ILI who have died, 
• patients where a diagnosis of influenza would affect clinical care, infection control, or
  management of contacts. 

•  Consider use of antivirals to quickly limit potential human transmission
•  Vaccinate patients and healthcare workers as a primary strategy to prevent influenza

 

As I wrote last month in What Lies Beneath, it appears that very limited human-to-human transmission of this virus may have occurred, but the virus does not yet appear capable of sustained and efficient human transmission.

 

The concern, of course, is that could eventually change. Hence the ongoing epidemiological investigation.

 

Below you’ll find excerpts from the CDC’s  SOIV page regarding these cases (reformatted for readability).

 

Reported Human Infections with Swine-Origin Influenza Viruses (SOIV) in the United States since 2005

As of September 9, 2011, 25 cases of human infection with swine origin influenza viruses have been reported in the United States. These are viruses that normally infect pigs. Like human influenza viruses, there are different subtypes and strains of swine-origin influenza viruses.

 

The main swine influenza viruses circulating in U.S. pigs in recent years are swine triple reassortant (tr) H1N1 influenza virus, trH3N2 virus and trH1N2 virus. Of the 25 human cases reported since 2005, 12 have been trH1N1 viruses, 12 have been trH3N2 viruses and one has been a trH1N2 virus.

 

All 25 persons infected with swine viruses recovered from their illness. Eighteen cases occurred in children (persons 18 or younger) and 7 cases occurred in adults. In 21 cases, direct or indirect exposure to swine prior to onset of illness has been identified.

 

Likely transmission of swine-origin influenza virus from close contact with an infected person has been observed in investigations of human infections with swine-origin influenza A virus, but has not resulted in sustained human-to-human transmission.

»» Read More

What Lies Beneath

 

Reassortant H3N2 virus detected in Pennsylvania & Indiana – Source CDC

 

 

# 5836

 

 

As a liveaboard sailor for several years on a very small -and extremely low-tech sailboat - I cruised without the modern luxuries of a LORAN, GPS, or even a depth meter.  Navigation was pretty much dead reckoning, and thin water . . .  well,  you often didn’t know you were in it until you heard the sickening sound of your keel scraping bottom.

 

While in the beginning it was unnerving - and its true I did run aground `a few times’ - after a while I began to accept that there are things that I can neither see or control.

 

After that, sailing became a lot more enjoyable.

 

Later, when I moved up to a much larger 32’ DownEast cutter, I had both a LORAN and a fathometer. Suddenly I could see threats on the bottom that had previously (and often blissfully) remained hidden.

 

While knowing the depth of the water was certainly desirable, and undoubtedly contributed to safer operation of my vessel, shoaling numbers on the LCD readout could also suggest imminent hazards that ultimately failed to materialize. 

  

Which is not unlike today, where increased disease surveillance, enhanced laboratory testing capabilities, and 24/7 internet reporting mean we often hear about disease threats far earlier than ever before.

 

 

Recently the CDC and the Pennsylvania Department of Health reported on the detection of 3 children with a novel H3N2 swine flu infection, while a fourth case was reported in Indiana (see CDC Update On The Pennsylvania Swine Flu Cases).

 

Although not unheard of, human infections by these novel swine flu viruses are considered pretty rare. Since 2005, we are aware of just over 2 dozen of them in the United States (see CDC SOIV page).

 

Most of the time, these viruses appear to be dead-end infections.  A person is exposed to an infected animal, contracts the virus - but since it is not particularly well adapted to human physiology - does not pass it on. 

 

Due to limited testing and surveillance over the years, how often that really happens is unknown.  But it may be more common than we think.

 

And it is not only possible, but probably likely, that very limited low-level human-to-human transmission of these novel viruses may occur from time to time. There is circumstantial to suggest that may be the case in the recent case in Indiana.

 

The concern is that – like we saw with the 2009 H1N1 swine flu –  a novel virus may adapt well enough to a human host to become easily transmissible. If that happens, and community immunity is low, and the virus is pathogenic in humans, a novel virus has the potential of sparking a pandemic.

 

So understandably, the CDC and and state public health agencies take these novel virus detections seriously. They conduct investigations to try to determine the source and to see if a virus has begun to transmit efficiently among humans.

 

So far the news on the Pennsylvania cluster remains encouraging. No new cases have been announced in more than a week. The investigation is ongoing, and so it is still possible that additional cases will be identified in the future.

 

This report from the Reading Eagle.

 

Novel virus strain in state is not outbreak, officials say

 

(EXCERPT)

 

"Everything that has come out so far suggests these are not easily transmittable," said Dr. Robert S. Jones, chief of infectious diseases at both St. Joseph Medical Center and Reading hospital.  " People shouldn't panic about that strain."

 

 

The caveat to all this good news is that influenza viruses are notoriously unstable, constantly mutating and evolve over time.

 

A virus that is poorly transmissible today may not remain so tomorrow.

 

So vigilance is key.

 

Missing from our knowledge base is just how often novel viruses like these emerge, sputter, and die out without ever causing recognizable outbreaks. In time we may discover that happens far more often than we have previously believed.

 

Like a sailor with a new fathometer, better surveillance tools and lab techniques make us more keenly aware of dangers that previously `passed beneath our keel’ unnoticed.

 

Certainly not a bad thing, but they can alert us to threats that never fulminate.

 

While these sporadic cases rightfully capture our attention, we may discover that (some-many-or most) of them are akin to `incidental findings’ often found on an MRI or CT scan – and ultimately have very little bearing on the public’s health.

 

How seriously we should regard these scattered detections of novel virus infections is something that only more research, experience, and time will reveal.

»» Read More

Pennsylvania DOH: Updated FAQ On The Novel Swine Flu Cluster

 

 

 

# 5818

 

 

The Pennsylvania Department of Health has updated their FAQ sheet (Q & A: Novel Influenza A Virus) on the recent detections of a reassorted H3N2 swine flu virus in three children who attended a county fair in mid-August.

 

It is still very early in the epidemiological investigation of these cases, and there are a lot of questions yet to be answered.

 

Prime among those is whether this virus has the potential to spread efficiently in humans.

 

For now, evidence of sustained human transmission has not been found.  Of course, the CDC is still investigating, and that could change if more cases show up.

 

But it is important to note, that even if a few more cases were to show up over the next few weeks, that wouldn’t necessarily mean that we are faced with an epidemic or pandemic situation. 

 

For that to happen the virus would need to be adapted well enough to human physiology to have an R₀ number (basic reproductive number) sufficient to sustain an outbreak.

 

The R₀  number signifies the average number of secondary infections caused by one infectious person entering a totally susceptible population. 

 

If less than 1.0, outbreaks are likely to sputter and die out.  If greater than 1.0, the outbreak is more capable of spreading. 

 

And as we’ve seen with roughly 20 other reported novel swine infections since 2005, and with a significant number of H5, H7, and H9 avian flu infections, it is possible to have limited outbreaks of a novel flu virus without it sparking an epidemic.

 

We’ll need to wait for more epidemiological evidence before we can know whether this particular virus has `legs’. If it is spreading efficiently (and that’s still a big `if’), we ought to see evidence of that fairly soon.

 

It is also possible that if this virus isn’t ready for prime time right now, that through further reassortment or mutation, it could become better adapted down the road. The only constant with influenza viruses is change.

 

So this situation deserves ongoing surveillance.

 

But regardless of this virus’s fate, the risks of seeing another novel pandemic virus emerge sometime in the future from either the farm or the wild are genuine.

 

 

A few recent blogs on this possibility include:

 

Professor Peter Doherty On Bird Flu

Two Reassortment Studies To Ponder

Hong Kong: Influenza Surveillance In Pigs

The (Swine) Influenza Reassortment Puzzle

 

 

The CDC’s investigation into these recent novel flu cases in Pennsylvania continues, and hopefully we’ll know more shortly.

 

Below are some excerpts from yesterday’s (9/6/11) updated Health Department FAQ. 

 

 

Questions & Answers: Novel Influenza A Virus

 
About the Flu Virus/Current Vaccination 

• 

What is this novel influenza A virus? 
Influenza A viruses occur in many animals, including humans, swine (pigs) and wild birds.This particular virus is unique from other previous H3N2 human infections in that it also contains a genetic piece of the 2009 H1N1 virus.

  
• Is it possible for humans to transmit it to other humans?  
Currently, it does not appear the virus is spreading from person‐to‐person.  However, we will continue to learn ore as our investigation into this new virus continues.  

•

How serious is this virus?  
We currently know of three cases of this novel influenza virus. One patient has recovered and the other two are recovering. Our investigation will continue to focus on the seriousness of the virus.  Based on what we know about other types of flu, illness can range from very mild symptoms to death in particularly susceptible populations (like older people, young children and those with certain medical conditions).

 

•  What does this mean for this year’s flu vaccines? Will the current vaccine cover both seasonal flu and this new strain of flu?  
The 2011‐2012 vaccine is the same as last year, covering two strains of influenza A pandemic H1N1 and a H3N2 strain that has been circulating for a few years now) as well as a strain of influenza B.  It is too early to tell whether or not this new strain will even need vaccination.  

<SNIP>

Should we be concerned that a flu pandemic is pending?  

A pandemic is a global outbreak of disease.  A flu pandemic happens when a new strain of the flu virus appears for which people have little or no immunity. As a result, it spreads easily from person to person around the world, causing widespread illness and death.

 

Currently, we don’t have any evidence to support that this novel influenza A virus will lead to a pandemic, as we haven’t yet been able to prove that it is being transmitted from human to human.

 

As with any new influenza A virus, public health officials  are working to learn more about the source of this particular strain and to determine how/if it can be spread from person to person. 

»» Read More

Pennsylvania Reports 2 More Novel Flu Cases

 

 

# 5814

 

 

In a press release this afternoon the Pennsylvania Health Department has announced the detection of two more novel swine flu infections among recent visitors to a county fair held in the southwestern part of the state.

 

This comes on the heels of the announcement on Friday in the CDC’s MMWR of two novel flu infections from a reassortant swine H3N2 virus that contained a gene segment from the H1N1 swine flu virus. 

 

In that announcement we were told of one case in Pennsylvania and another case in Indiana, both of whom had recovered.  All of the cases so far have involved children.

 

Today’s development will no doubt inspire intense state and federal epidemiological investigations to see if this new strain of flu has acquired the ability to spread efficiently from human to human.

 

So far, these appear to be isolated infections with no evidence of secondary transmission of the virus in Pennsylvania, although there are indications that may have occurred in the one case from Indiana.

 

 

 

 

Novel Influenza-A Cases Linked to County Fair; Pennsylvanians Should Continue Flu Prevention Practices and Report Flu-like Illness

HARRISBURG, Pa., Sept. 5, 2011 /PRNewswire/ -- The Pennsylvania departments of Health and Agriculture today announced three cases of a novel influenza A virus have been identified, and are now linked to an agricultural fair in southwestern Pennsylvania.

 

The first individual to become ill, announced on Friday, Sept. 2, has fully recovered from the illness. Two other individuals, confirmed ill over the weekend, are recovering. All three are children who reported attending the Washington County Agricultural Fair the week of Aug. 13-20, 2011.

 

The cases in Pennsylvania are similar to previous, rare human infections with swine-origin H3N2 viruses, but are unique in that they contain a genetic component of the H1N1 virus.

 

A continuing investigation, which is being jointly undertaken by the departments of Health and Agriculture, as well as the Centers for Disease Control and Prevention (CDC), has not yet uncovered how the illness was transmitted to the three individuals.  However, no additional human infections with this virus have been identified to date.

 

Anyone who attended the Washington County Fair and has flu-like symptoms should contact their local health care provider or call 1-877-PA-HEALTH. Symptoms would be similar to that of seasonal influenza, and would include fever, lethargy (extreme tiredness), lack of appetite and coughing. Other influenza symptoms may include a runny nose, sore throat, eye irritation, nausea, vomiting and diarrhea.

 

The Department of Health and the CDC are conducting increased surveillance and tracking in southwestern Pennsylvania, as well as setting up informational booths about influenza at agricultural fairs, while Department of Agriculture is continuing with monitoring the health of animals at all exhibitions.

 

The Department of Health continues to urge the public to take everyday precautions to prevent the spread of respiratory viruses, while the Department of Agriculture reminds residents to remember to wash your hands after coming into contact with animals at fairs and in other public venues.

 

"We're not telling people to avoid public venues or fairs," said Pennsylvania DOH Secretary Dr. Eli Avila. "But, until we complete our investigation, we want to make sure that the public is aware and is taking the proper precautions to protect their health."

 

Everyday preventative actions against influenza include:

• Coughing or sneezing into a tissue, your sleeve or elbow (not your hands);  
• Washing your hands often with soap and water for at least 20 seconds, especially after you cough or sneeze, or using an alcohol-based hand cleaner;
• Keeping your hands away from your face – don't touch your mouth, hands or eyes;
• Keeping frequently used surfaces clean; and
• Staying home from work, school, and social gatherings if you have flu-like and feverish symptoms to help prevent others from catching your illness.

For more information, visit www.health.state.pa.us or call 1-877-PA-HEALTH.

»» Read More

CIDRAP On Today’s Reassorted Swine Flu Story

 

 

# 5809

 

 

Robert Roos, News Editor for CIDRAP has an excellent summary of today’s big story about two recent infections from a previously unseen novel swine flu virus (see MMWR: Two Novel trH3N2 Flu Infections and MMWR: Swine-Origin Influenza A (H3N2) Virus Infection in Two Children).

 

Roos also includes some comments from Lyn Finelli, DrPH, chief of the surveillance and outbreak response team in the CDC's influenza division and Andrew T. Pavia, MD, chief of the Division of Pediatric Infectious Diseases at the University of Utah in Salt Lake City.

 

 

Novel H3N2 swine flu viruses infected 2 children, CDC says

Robert Roos News Editor

Sep 2, 2011 (CIDRAP News) – In separate instances, influenza A/H3N2 viruses circulating in swine picked up a gene from the pandemic 2009 H1N1 virus and recently infected two young children, one in Indiana and one in Pennsylvania, the Centers for Disease Control and Prevention (CDC) reported today.

Both of the children recovered, though one was briefly hospitalized, and there is no sign that the viruses spread from the children to others, but any evidence of ongoing transmission would require a rapid response, the CDC said.

The agency also said one of the children had no direct contact with pigs, which suggests he caught it from another person. Both children are under age 5.

(Continue . . . )

 

»» Read More

CDC: Another Novel H3N2 Isolate

 

 

# 5155

 

 

While influenza activity across most of the country is reported as low, with moderate activity reported primarily in the Southeastern states, there is some news in this week’s FluView report which is bound to get a lot of attention.

For the 6th time in two years, a novel H3N2 swine-type influenza has been detected in the United States.

 

As you may recall, just over a month ago we learned of two other novel H3N2 infections (see CDC: Statement On Swine H3N2 Influenza) in Wisconsin and Pennsylvania.

 

The CDC has issued a statement on this latest discovery, which I’ve linked to and excerpted below.  But since this is a lengthy statement, I’ve pulled some bullet points out:

 

 

• Test samples from one patient in Minnesota were confirmed at CDC as positive for swine origin triple-reassortant (tr) H3N2 influenza viruses—viruses that normally infect pigs.
• Although human infection with swine influenza viruses is rare, it can occur.
• The patient in Minnesota with confirmed trH3N2 infection had exposure to pigs prior to illness onset.
• There is no documented human-to-human transmission of this virus or any evidence of community transmission at this time.
• An investigation of this case is ongoing.
• Cases of human infection with swine influenza viruses underscore the importance of ongoing human and animal influenza surveillance.
• The most recent Minnesota case brings the number of reports swine origin A (H3N2) infections in humans in the United States to six.
• Human infections with swine origin H3N2 virus infections have also been reported from Pennsylvania and Wisconsin in October and November 2010, Minnesota in May 2010, Iowa in September 2009, and Kansas in August 2009.

 

Follow the link to read this statement in its entirety. 

 

December 17, 2010

Report of Human Infection with Swine Origin Influenza A (H3N2)

The December 17, 2010 FluView reported one human infection with swine origin influenza A (H3N2) virus in the state of Minnesota as part of U.S. surveillance and reporting of novel influenza A viruses. Test samples from one patient in Minnesota were confirmed at CDC as positive for swine origin triple-reassortant (tr) H3N2 influenza viruses—viruses that normally infect pigs. Although human infection with swine influenza viruses is rare, it can occur. This is most likely to occur when people are in close proximity to infected pigs, such as in pig barns and at livestock exhibits housing pigs at fairs. The patient in Minnesota with confirmed trH3N2 infection had exposure to pigs prior to illness onset. There is no documented human-to-human transmission of this virus or any evidence of community transmission at this time. An investigation of this case is ongoing. Cases of human infection with swine influenza viruses underscore the importance of ongoing human and animal influenza surveillance.

 

This case of human infection with swine origin influenza virus (SOIV) brings the total number of human infections with swine origin influenza viruses reported to CDC since 2005 to 19. Previously, five of these reports had been swine origin A (H3N2) viruses. The most recent Minnesota case brings the number of reports swine origin A (H3N2) infections in humans in the United States to six. Human infections with swine origin H3N2 virus infections have also been reported from Pennsylvania and Wisconsin in October and November 2010, Minnesota in May 2010, Iowa in September 2009, and Kansas in August 2009.

 

Swine influenza (swine flu) is a respiratory disease of pigs caused by type A influenza viruses that regularly cause outbreaks of influenza in pigs. Swine flu viruses can result in high illness rates in pig herds, but generally cause few deaths in pigs. Swine influenza viruses can circulate among pigs throughout the year, but most outbreaks occur during the late fall and winter months, similar to outbreaks in humans. There are four main influenza type A virus subtypes that have been isolated in pigs: H1N1, H1N2, H3N2 and H3N1. Most flu viruses circulating in pigs are referred to as "triple-reassortant" viruses because these flu viruses contain genes from human, swine and avian influenza viruses.

 

(Continue . . . )

 

For more information about swine influenza, visit http://www.cdc.gov/flu/swineflu/

Weekly U.S. surveillance updates are published in FluView and posted at

http://www.cdc.gov/flu/weekly/fluactivitysurv.htm

 

 

 

While obviously of considerable interest (and perhaps, even a modicum of concern) I would remind my readers that only a tiny fraction of flu viruses are ever sequenced, and so we really don’t know how often these types of infections occur.

 

Probably more often than we think, would be my guess.  And most apparently never go anywhere.

 

Otherwise we’d be be hip deep in novel H3N2 swine flu infections.

 

Swine have been long viewed as excellent `mixing vessels’ for influenza, but that process can take a long time before a `fit’ human adapted virus is produced.  Novel H1N1 apparently bounced around in pigs for more than a decade before jumping to humans.

 

All of this highlights the need for upgraded, and continual surveillance of humans, and livestock, for emerging viral threats.   

 

Because it isn’t if the next pandemic will emerge. It’s only a matter of when.

»» Read More