Multiple introductions of avian influenza viruses (H5N1), Laos, 2009-2010.

Avian influenza viruses (H5N1) of clades 2.3.4.

Susceptibility of highly pathogenic H5N1 influenza viruses to the neuraminidase inhibitor oseltamivir differs in vitro and in a mouse model.

While the neuraminidase (NA) inhibitor oseltamivir is currently our first line of defense against a pandemic threat, there is little information about whether in vitro testing can predict the in vivo effectiveness of antiviral treatment. Using a panel of five H5N1 influenza viruses (H5 clades 1 and 2), we determined that four viruses were susceptible to the drug in vitro (mean 50% inhibitory concentration [IC(50)], 0.1 to 4.

Evolution and adaptation of H5N1 influenza virus in avian and human hosts in Indonesia and Vietnam.

Highly pathogenic avian influenza virus H5N1 is endemic in poultry in East and Southeast Asia with disease outbreaks recently spreading to parts of central Asia, Europe and Africa. Continued interspecies transmission to humans has been reported in Vietnam, Thailand, Cambodia, Indonesia and China, causing pandemic concern. Here, we genetically characterize 82 H5N1 viruses isolated from poultry throughout Indonesia and Vietnam and 11 human isolates from southern Vietnam together with sequence data available in public databases to address questions relevant to virus introduction, endemicity and evolution.

Distribution of amantadine-resistant H5N1 avian influenza variants in Asia.

We examined the distribution of genetic mutations associated with resistance to the M2 ion channel-blocking adamantane derivatives, amantadine and rimantadine, among H5N1 viruses isolated in Vietnam, Thailand, Cambodia, Indonesia, Hong Kong, and China. More than 95% of the viruses isolated in Vietnam and Thailand contained resistance mutations, but resistant mutants were less commonly isolated in Indonesia (6.3% of isolates) and China (8.

Establishment of multiple sublineages of H5N1 influenza virus in Asia: implications for pandemic control.

Preparedness for a possible influenza pandemic caused by highly pathogenic avian influenza A subtype H5N1 has become a global priority. The spread of the virus to Europe and continued human infection in Southeast Asia have heightened pandemic concern. It remains unknown from where the pandemic strain may emerge; current attention is directed at Vietnam, Thailand, and, more recently, Indonesia and China.

Are ducks contributing to the endemicity of highly pathogenic H5N1 influenza virus in Asia?

Wild waterfowl are the natural reservoir of all influenza A viruses, and these viruses are usually nonpathogenic in these birds. However, since late 2002, H5N1 outbreaks in Asia have resulted in mortality among waterfowl in recreational parks, domestic flocks, and wild migratory birds. The evolutionary stasis between influenza virus and its natural host may have been disrupted, prompting us to ask whether waterfowl are resistant to H5N1 influenza virus disease and whether they can still act as a reservoir for these viruses.

Role of domestic ducks in the propagation and biological evolution of highly pathogenic H5N1 influenza viruses in Asia.

Wild waterfowl, including ducks, are natural hosts of influenza A viruses. These viruses rarely caused disease in ducks until 2002, when some H5N1 strains became highly pathogenic. Here we show that these H5N1 viruses are reverting to nonpathogenicity in ducks.