New England Seal Deaths Tied to H3N8 Flu Virus

 

 

# 6022

 

We’ve a follow up from NOAA today on the mysterious deaths of seals along the New England coastline earlier this fall.  In early November I reported (see NOAA: New England Dead Seals Test Positive For Flu) that initial tests indicated an influenza A virus, but more testing was needed to determine the exact strain.

In the past, we’ve seen rare and isolated influenza infections resulting in seal deaths from the H7N7 and H4N5 avian flu viruses.

 

Today we learn that the viral culprit in this latest incident is a variant of the H3N8 avian flu strain, versions of which are known to also infect horses and dogs.

 

My thanks to @JustinNOAA for the link to this news release.

 

 

Science team identifies influenza virus subtype that infected five dead seals

Risk to humans and pets low; tests continue

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Harbor Seals (Credit NOAA)

A virus similar to one found in birds but never before in harbor seals was the cause of five of 162 recent deaths of the animals  in New England, according to a group of federal agencies and private partners.

 

This Influenza A virus subtype, H3N8, appears to have a low risk of transmission to humans. Experts continue to analyze this virus, and any findings of public health significance will be immediately released. The virus is not the infamous H5N1  virus that caused a global pandemic in 2007, or the H1N1 virus from 2009.

 

Any member of the public who sees a seal in distress is reminded to:

• Stay at least 150 feet away
• Keep dogs leashed and away from seals
• Call NOAA Fisheries Service's stranding hotline at 1-866-755-NOAA (6622)

“The work that NOAA and its partners have done to help identify and confirm the virus strain H3N8 in these animals has been an important first step in the investigation into this event,” said Dr. Teri Rowles, lead veterinarian and coordinator of the Marine Mammal Health and Stranding Program for NOAA Fisheries Service. “We are now conducting tests on additional animals to learn more about the role this virus may have played in the die-off and to better understand the virus itself.”

 

Experts believe that Influenza A virus caused a bacterial pneumonia which was responsible for the death of the five seals. Most terrestrial animals infected with the previously known H3N8 virus suffered upper respiratory infections, and most recovered.

 

"This H3N8 virus is usually associated with wild birds, and a separate group of H3N8 infects horses and dogs,” said Dr. Hon Ip, of the USGS’s National Wildlife Health Center. "This is the first time that a virus which is similar to the H3N8 avian influenza virus has been associated with a large scale mortality in marine mammals."

(Continue . . . )

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Maine Confirms A 2nd trH3N2 Case

 

 

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

 

Although it doesn’t seem to happen terribly often, every once in awhile an avian or swine influenza virus manages to infect a human host.

 

Usually after direct close contact with a bird or or pig.

 

This is a pattern we’ve seen with the avian H5N1, H9N2, and H7N7 viruses, and we’ve also seen it a couple of dozen times since 2005 with SOIV (swine origin influenza virus) trH1N1 and trH3N2 strains. 

 

Most of the time, these infections turn out to be dead end transmissions, as the virus is only partially adapted to human physiology.

 

Occasionally, we’ve seen evidence of limited secondary transmission albeit not in a sustained and efficient manner.

 

A recent `exception to this rule’ was the 2009 H1N1 pandemic virus, which after bouncing around in the swine population for years, finally evolved into an easily transmissible human pathogen.

 

If it were an easy thing for viruses to do, we’d be hip deep in pandemic viruses all of the time. It apparently takes a lot of evolutionary trial and error before a virus can `get it right’.

 

 

Although few of these avian and swine viruses have adapted well enough over the years to pose a serious public health threat, we watch them with great interest because the potential exists for them to eventually `figure us out’.

 

Over the past 90 days or so, we’ve been keeping up with a new SOIV virus has been detected among a small handful of people across three states. This virus is a reassortment of a swine trH3N2 and the 2009 pdmH1N1 virus.

 

You can find earlier coverage of these cases in A 5th trH3N2 SOIV Report & CDC Update On trH3N2 Cases.

 

Today the state of Maine’s website has news of their 2nd case detected during the month of October. It can be found in their weekly influenza surveillance report dated November 1st.

 

Novel Influenza A Virus

•  Maine confirmed a second case of swine origin novel influenza A virus. The first case was confirmed on October 17th , and the second case was confirmed October 31st. Both cases had multiple exposures to pigs.

 

These cases are the 5th and 6th recognized cases of human infection with S-OtrH3N2 with the M segment gene from the pH1N1virus.

 

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. 

 

 

Epidemiological investigations into these cases continue. 

 

While sporadic cases such as these are not particularly alarming, we do watch these infrequent viral escapees from the farm for signs of adaptation.

 

As long as they are not able to transmit efficiently among humans they pose a very low public health threat. 

 

The concern is that the odds favor that the next pandemic virus will come from a farm – where large numbers of animals intermingle, swap viruses, and come in daily contact with humans.

 

Which is why so many scientists are calling for more comprehensive testing and surveillance on farm animals. 

 

For more on the reassortment potential of avian, swine, and human flu viruses, you can’t do better than  Helen Branswell’s excellent Scientific American article from last December called Flu Factories, or her SciAm Podcast interview.

 

For some of my earlier posts on this newly discovered trH3N2 swine flu virus, you may wish to revisit:

 

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

MMWR: Two Novel trH3N2 Flu Infections

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