Bird Flu (H3N8) blamed for seal deaths

[Catbird]

MedPage:

"In the wake of a pneumonia outbreak that killed 162 harbor seals in New England last year, researchers are blaming the deaths on an avian flu virus.

The virus is similar to one circulating in North American birds since 2002 but shows signs of having recently adapted to mammals, according to according to Ian Lipkin, MD, of Columbia University's Mailman School of Public Health in New York City and colleagues.

Among the adaptations are some genetic changes that have been associated with increased virulence and transmissibility among mammals, Lipkin and colleagues reported in the July/August issue of the journal mBio.

The outbreak is "particularly significant," they wrote, because the virus has naturally acquired mutations that may make it a candidate to cause disease in humans.

...Five animals were collected for testing; all had pneumonia and ulcers on the skin and oral mucosa, Lipkin and colleagues reported. Genetic testing also showed that all five were positive for influenza A.

When the investigators sequenced the genes for the viral proteins hemagglutinin and neuraminidase, they found the flu was subtype H3N8, typically found in birds, but also in horses and dogs.

The virus is closely related to one isolated in 2002 from a blue-winged teal in Ohio – the two are identical in 96.07% of their respective genomes.

But the 37 changes in amino acid sequence from the older subtype to the seal virus include several that are potentially worrisome, the researchers said.

For instance, the second RNA segment of the virus encodes the PB1 protein and in some strains a second protein, dubbed PB1-F2, which has been associated with increased cell death, inflammation, and secondary bacterial pneumonia.

The 2009 pandemic H1N1 flu lacked the PB1-F2 protein, which some experts have suggested may have limited its virulence.

The seal H3N8 virus, on the other hand, has the protein – and all five tested seals had evidence of apoptosis and secondary bacterial pneumonia.

The genetic sequences were also missing a section whose deletion – previous work on the highly pathogenic H5N1 avian flu has shown – is associated with the ability of influenza to use human-like cellular receptors and to transmit among mammals.

The seal virus also has a mutation – dubbed D701N – that has been experimentally shown to increase pathogenicity and transmissibility. In previous seal flu outbreaks, the mutation was absent, but it is commonly found in H3N8 viruses in horses and dogs, the researchers reported."

[Kassy]

Thanks!

Yet another flu to watch. So now we have H3N2 jumping from swine to pigs in the US for the second year in a row, H5N1 still around & now this rather impressive H3N8 bird flu.

2 articles:

http://www.cbsnews.com/8301-504763_1...ead-to-humans/

http://www.foxnews.com/health/2012/0...h-experts-say/

In the last one they talk about bird receptors/human receptor cells for flu.


Bird flu prefers alpha 2,3 sialic acid receptors while human flu prefers alpha 2,6 type.

Both pigs and seals have a mix of these which allows the virus to change preference.
It's not either/or because humans have the 2,3 type too but in different places (lower in the lungs).

For more on this subject:
http://www.virology.ws/2009/05/05/in...-sialic-acids/

[CanadaSue]

Don't like the way this one is shuffling the cards in its deck.

More & more - a few seasons later, I'm getting the feeling that the 2009 H1N1 pandemic was more along the lines of a 'pre-pandemic'. If you'll pardon me a moment of whimsy, it "wiped the flu virus blackboard almost clean" of the then predominant strains. Those were forced into the background where they had to - "adapt or fade into history for a time". Given their druthers, flu viruses will adapt... every time. Yeah, they're always adapting but now the new bully on the block - pH1N1 - was in their face. If they wanted to get back in the game, they had to figure out a way to get back on the playground. Sounds like H3N2 has learned that lesson, judging by southern hemisphere reports.

And if you're into the notion of a natural balance, a yin/yang, holes to be filled, vacuums being abhored - there's a whole lot of room right now for contenders to try the big boys on for size, shuffling, juggling, trying out new species & orders of life for lunch & seeing what they can make work. I'm thinking a few new or newish strains have amost got it figured out & then we're gonna see a viral battle in the hood... following which, the victor will turn on us.

[Kassy]

Published Date: 2012-08-01 17:37:20
Subject: PRO/AH/EDR> Influenza - USA (60): (New England) H3N8, seals, human potent.
Archive Number: 20120801.1224334

INFLUENZA - USA (60): (NEW ENGLAND) H3N8, SEALS, HUMAN POTENTIAL
************************************************** **************
A ProMED-mail post
http://www.promedmail.org
ProMED-mail is a program of the
International Society for Infectious Diseases
http://www.isid.org


Date: Tue 31 Jul 2012

Source: CIDRAP News [abbreviated & edited]

http://www.cidrap.umn.edu/cidrap/con...2se=alflu.html





A research team that analyzed the strain of H3N8 influenza virus linked to a baby seal die-off in New England last year [2011, see ProMED-mail archived reports below] found that it originated in birds and has adapted to mammals, signalling a possible threat to humans and animals alike. The study, which appeared today [31 Jul 2012] in the mBio, the online journal of the American Society for Microbiology (ASM), also revealed mutations that are known to make flu viruses more transmissible and able to cause severe disease. [Anthony SJ, St Leger JA, Pugliares K, et al. Emergence of fatal avian influenza in New England harbor seals. mBio 31 Jul 2012, http://mbio.asm.org/content/3/4/e00166-12.full.]



In December 2011, scientists with the National Oceanic and Atmospheric Administration (NOAA) announced that an investigation of 162 seal deaths that fall revealed the H3N8 virus in samples from all 5 animals studied, the 1st time the strain had been linked to large-scale mortality in marine mammals. The infected seals had severe pneumonia and skin lesions, and most of them were less than 6 months old.



Influenza H3N8 is typically associated with wild birds, but in 2005, researchers found that a type of the strain that emerged in racing greyhounds had jumped from horses to dogs. The illness in dogs is generally mild and hasn't posed any known danger to humans. Genetic and phylogenetic analysis of samples from the seals found that the virus was an avian subtype that was similar to one that has infected North American waterfowl since 2002 but has adapted to mammals with mutations that make it more transmissible and pathogenic. Scientists gave the new virus the provisional name influenza A/harbor seal/Massachusetts/1/2011. The group found mutations previously detected in H5N1 viruses that infected humans and wrote that the H3N8 virus in seals had acquired the ability to bind sialic acid receptors that are commonly found in mammal respiratory tracts. Though the mutations are required for cell entry and replication in mammals, researchers wrote that more studies are needed to assess their functional significance. Adaptations found in the study suggest the virus may be able to persist in seals and evolve into a new H3N8 clade, similar to what occurred with the canine and equine viruses, they reported.



The researchers concluded that natural emergence of a pathogenic virus that can transmit between mammals, and in a species that can be infected with multiple flu subtypes, is considered a significant threat to wildlife and human health. They added that monitoring viruses such as the H3N8 strain found in seals is crucial, because it can help scientists better predict the emergence of new strains and prevent future pandemics.



Ruben Donis, PhD, chief of the molecular virology and vaccines branch in the US Centers for Disease Control and Prevention's (CDC's) Influenza Division told CIDRAP News that the CDC received viral samples obtained from the seals several months ago and analyzed them with additional methods as part of its own risk assessment. He said overall, the virus appears to pose a low risk to humans with a low probability of causing zoonotic infections.



CDC officials have discussed issues surrounding the new virus with wildlife rescue teams and have emphasized precautions that personnel should take when working with the animals and requested that they obtain samples if they see seals that appear to have pneumonia. "We plan to keep in touch and follow up," Donis said.



Ian Lipkin, MD, director of Columbia University's Center for Infection and Immunity and coauthor of the mBio study, said in a university press release that the findings reinforce the importance of wildlife surveillance. "HIV/AIDS, SARS, West Nile, Nipah, and influenza are all examples of emerging infectious diseases that originated in animals. Any outbreak of disease in domestic animals or wildlife, while an immediate threat to wildlife conservation, must also be considered potentially hazardous to humans," he said.



[Byline: Lisa Schnirring]



--

Communicated by:

ProMED-mail Rapporteur Kunihiko Iizuka

[To put these observations in perspective, despite circulation of influenza A viruses of 16 HA types in billions of birds over a very long time span, the 4 pandemics in the last century have been restricted to influenza viruses bearing the HA types H1, H2 or H3. Decades ago, many experts predicted that influenza pandemics could be explained by "recycling" of a small number of HAs in new human generations. Most recently, this belief has been expanded to posit that the other HA types (including H5) are fundamentally incapable of adapting to humans, being selected against by biological constraints or unappreciated selection pressures.



Despite widespread influenza virus circulation and dynamic evolution of the human-animal interface, with many billions of quasi-species, mutations and gene constellations circulating, only 4 influenza pandemics have occurred in the last century, and in the 3 of those with a known viral origin, the viruses resulted from reassortment of pre-existing human or swine viruses, not by mutation or adaptation of existing avian viruses. This suggests that the _de novo_ emergence of a human pandemic influenza virus is an extremely rare event that is not easily achieved in nature. (From: Morens, Subbaro and Taubenberger, Nature doi:10.1038/natur11170, Nature 21 Jun 2012).

It remains to be seen whether the H3N8 virus, common in birds, which has appeared sporadically in canines, equines, and now in seals, will pose any greater threat to the human population.



The interactive HealthMap/ProMED map for New England is available at: http://healthmap.org/r/1xMA. - Mod.CP]




See Also

http://www.promedmail.org/direct.php...120801.1224334

Those ProMed Mod's are so level headed.

[Catbird]

Originally Posted by Kassy

Those ProMed Mod's are so level headed.

I agree. They're just sooo boringly logical.

But I learned something new today in an NY Times article about this. Apparently, if I'm understanding this correctly, seals are like pigs in that they have both alpha 2,3 and alpha 2,6 receptor cells. So, theoretically at least, reassortment could happen in seals, just as it does in swine.

"Pigs, Dr. Lipkin noted, are especially good at producing new flu strains because they can be infected by bird flu and mammal flu at the same time. Two kinds of virus can combine, giving rise to new hybrid strains.

Dr. Lipkin and his colleagues found evidence that seal cells can also be invaded by both kinds of viruses — raising the possibility that they could produce new hybrid flu strains as well.

“It could be the equivalent of an aquatic pig,” Dr. Lipkin said. "

After re-reading the ProMed report, I see that it's kind of vaguely mentioned, "...in a species that can be infected with multiple flu subtypes...". I didn't pick up on that the first time around but it makes more sense now.