Webby On H7N9: `Clear Evidence Of Mammalian Adaptation’

 

Site of recent H7N9 infections

 

# 7059

 

 

Helen Branswell has an important report overnight which includes comments from world renown influenza researcher Richard J. Webby, CIDRAP director Michael T. Osterholm, Gregory Hartl of the World Health Organization, and   Dr. Barbara Raymond, director for pandemic preparedness at PHAC.

 

Dr. Richard Webby -  who became director of the World Health Organization’s Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds at St. Jude Children’s Hospital in Memphis, Tennessee in 2008 - has been highlighted often in this blog.

 

A few recent examples include:

1. Dr. Richard Webby Lecture: Emerging Flu Viruses In The Animal World

2. PLoS Pathogens: A New Influenza C Virus Detected In Swine

3. Egypt: A Paltry Poultry Vaccine

4. PNAS: Virulence & Transmissibility Of H1N2 Influenza Virus In Ferrets

5. Interspecies Transmission Of Canine H3N2 In The Laboratory

 

Webby sees worrying signs of adaptation of the H7N9 virus to mammals – an indication that the virus may now be hosted by non-avian species – like pigs, or humans.

 

Since no one does a flu report better than Helen, at this point I will wisely step aside and invite you to read:

 

New flu virus in China shows signs it has adapted to mammals: Will it take off?

By: Helen Branswell, The Canadian Press

Review: Evolution & Adaptation Of The 2009 pdmH1N1 Virus

 

 

# 5704

 

A comprehensive review today of the history - and possible future evolution - of the 2009 H1N1 pandemic virus, by Richard J. Webby PhD, et al. from the Department of infectious Diseases at St Jude Children’s Research Hospital in Memphis, Tennessee. 

 

Dr. Webby is also Director of the World Health Organization’s  Collaborating Center for Studies on the Ecology of Influenza in Animals and Birds. 

 

This review appears in the July 15th edition of  Virus Adaptation and Treatment, a Dovepress open access, peer reviewed journal on scientific and medical research.

 

The 9-page review may be accessed at the following link.

 

Evolution and adaptation of the pandemic A/H1N1 2009 influenza virus

Review

Authors: Ducatez MF, Fabrizio TP, Webby RJ

Published Date July 2011 Volume 2011:3 Pages 45 - 53

DOI: http://dx.doi.org/10.2147/VAAT.S9656

 

 

There is so much good content packed into this review, it would be difficult to summarize it here.  Webby, et al. cover such topics as:

 

• Evolution and adaptation of A(H1N1)pdm09 viruses in human and swine
• Genetic drift
• Antigenic variation
• Reassortment in humans
• Reassortment in swine
• Reassortment in experimental models

• Replication, transmission,and virulence of pandemic A(H1N1)pdm09 viruses
• Transmission in animal models
• Molecular markers of virulence

• Drivers of future evolution and adaptation
• Evolutionary rates
• Vaccination
• Antiviral drug use

 

Fortunately, it is short enough, and readable enough – even for those with a limited background in influenza science - that it really doesn’t require a condensed version from me.

 

But briefly . . . 

 

While the first 18 months of the spread of the 2009 pdmH1N1 virus showed very little genetic diversity, over the past 6 to 8 months the WHO’s GISN has detected “increased heterogeneity”  (diversity) among H1N1 isolates tested. 

 

For now, the vaccine strains selected for this fall’s vaccination campaign in the Northern Hemisphere remain a good antigenic match to the vast majority of the influenza A viruses now in circulation.

 

Over time, history tells us that will change.

 

Since influenza viruses leave their hosts with protective antibodies, they must either evolve to evade those antibodies, or die for a lack of susceptible hosts.

 

It is also possible that changes in transmissibility and virulence may also occur as the virus adapts and evolves.

 

As the authors write in their conclusion:

 

The presence of this virus in swine, the propensity for swine to support reassortment, and the known ability, albeit limited, of viruses to move between swine and humans, create an opportunity for these substantial changes to occur.

 

For anyone with even a passing interest in the evolution of influenza viruses in general, and of the likely future of the pandemic H1N1 virus in particular, this review is highly recommended.