H7N9’s Lineage

An analysis of the novel virus indicates it’s descended from at least four different bird flu strains.

By | May 2, 2013


The novel H7N9 virus that has been infecting people in China since February likely got its genes from at least four different bird viruses, according to a paper published yesterday (May 1) in The Lancet. Chinese researchers determined the virus’s history by looking at sequences of four different viral isolates from infected patients.

The virus was first identified a little over a month ago and has infected 126 people and killed 24, according to the World Health Organization’s latest numbers. It has been found in chickens, ducks, and captive-bred pigeons at live animal markets, where it is suspected to have infected many of its victims.

The numbered Hs and the Ns in flu viruses’ names come from two proteins: hemagglutinin (HA) and neuraminidase (NA). The HA protein helps the virus latch on to host cells, while the NA protein is necessary for the virus to bud out of a cell following replication. Viruses are composed of HA, NA, and internal sequences, and they can shuffle their genes amongst each other, in a process called reassortment.

The Chinese scientists attempted to match the sequences the viruses’ components to previously sequenced flu virus strains from animals. The H7 component of the virus likely came from avian flu in a ducks and matches most closely to ducks in the Zhejiang Province, they concluded. The closest matches for N9 were the NA proteins of avian viruses from wild ducks sampled in 2011 in South Korea. These animals are known to migrate regularly between China and Korea.

The scientists say that the wild birds carrying H7 and N9 viruses likely passed them to domesticated poultry, where they recombined into the H7N9 virus that is infecting people today.

The internal genes of the virus appeared to come from two different H9N2 viruses from chickens in China. Hinting at an earlier recombination event, the polymerase genes of the virus, which help it replicate, appear to be related to virus from a wild migratory bird called a brambling.

 “[L]ow pathogenicity in avian hosts probably allowed the virus to spread silently in domestic and wild birds,” Belgian virologists Marc Van Ranst and Philippe Lemey woret in a commentary accompanying the Lancet article.  “Containing this hidden epidemic might prove very challenging in view of the magnitude of the domestic and wild bird populations in China.”

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Avatar of: David Fedson

David Fedson

Posts: 2

May 2, 2013


Influenza scientists and health officials are concerned about the pandemic threat posed by the emergence of a novel influenza A (H7N9) virus. Efforts have begun to develop a vaccine, but it is important to note that in the 2009 H1N1 pandemic, vaccination in the US prevented only 3-4% of all pandemic cases, hospitalizations and deaths. Moreover, more than 90% of the world's people had no access to pandemic vaccines or existing antiviral agents. Thus, by all measures, the global response to the 2009 pandemic was a comprehensive failure. If the H7N9 virus evolves to become easily transmissible between humans, another pandemic is certain, and it is naive to think the global response will be any different now than it was in 2009. Moreover, a call to develop new antiviral agents overlooks the long time frame from development to licensure, the high cost of any newly licensed agent, and consequently its availability only to people who live in developed countries. What influenza scientists, health officials and journalists have ignored is the ready availability of potentially effective agents that could improve survival in a pandemic. In an observational study of 3043 patients hospitalized with laboratory-confirmed influenza, statin treatment was associated with a 41% reduction in 30-day mortality, a reduction that was in addition to any that might have been attributable to previous vaccination and antiviral treatment. Surprisingly, influenza scientists have ignored this study, and health officials have shown no interest in extending these earlier findings. Yet, in a randomized controlled trial, giving statins to ward patients admitted with sepsis reduced progression to severe sepsis from 24% to 6%. Statins and other immunomodulatory agents are produced generically and available to anyone with access to basic health care anywhere in the world. The cost of treating an individual patient would be less that one dollar. Given what we already know, journalists and citizens must ask influenza scientists and health officials why they continue to ignore the remarkable promise of immunomodulatory treatment for influenza patients.     


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