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Evolving H5N1 In Northern Vietnam Sent To US For Analysis

Recombinomics Commentary

April 15, 2005

>> Nguyen Tran Hien, director of the National Institute of Hygiene and Epidemiology, said he had already taken nearly 1,000 blood samples from patients, poultry, water birds and other animals in order to discover a distribution map of the H5N1 virus.

Hien said the H5N1 virus of this year is very different with that of the previous year.

While the toxicity has reduced, the spread is definitely faster. Samples have already been sent to the US for further testing, with results expected by the end of this week. <<

The comment that the H5N1 was very different and had reduced toxicity matches the analysis of news reports.  In the south, all confirmed cases have been fatal, in Vietnam and Cambodia.  In contrast, most of the patients in the north recover.  However, these milder cases have been associated with more efficient spread.

Although the above comments do not define the mix of human and animal samples or give the locations, the shipment of samples to the US for further testing suggests serious changes that may complicate management of H5N1.

There were detection issues in the south and changing of the H and N could create detection issues in the north as well.  A large number of samples from Quang Binh were sent to the National Institute of Hygiene and Epidemiology three weeks ago, and results have not been released.  Samples were also sent from the neighbors of the family of five in Haiphong that tested positive for H5N1.  In these large clusters, most of the patients had relatively mild symptoms, which could allow transmission to blend in with human flu and go unnoticed in the absence of testing and deaths.

Difficulties in monitoring H5N1 could lead to greater problems because of the large number of respiratory cases, which if caused by human influenza, could provide opportunities for further evolution via dual infections.  Thus, a large population of H5N1 infected patients could lead to increased genetic instability, especially if the disease is mild and infected patients are transmitting for longer time periods than those who are severely ill and confined to bed at home or in the hospital.

The shipment of samples to the US for further testing, signals a change, and the comment that the spread is definitely faster could signal more problems in the near term.  The analogies with the 1918 pandemic are hard to ignore.  The rapid spread and high death rate in the fall was preceded by a mild flu outbreak in the spring.  The mild outbreak could have distributed a less lethal version worldwide, followed by recombination to produce lethal versions that quickly created the pandemic.

Publication of the novel sequence data would be useful.  H5N1 has been evolving in the absence of reassortments with human genes, and the evolution has been more subtle than has been described in recent accounts of the 2004 sequences.

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