Is bird flu virus evolving into something much more dangerous?

Main Category: Bird Flu / Avian Flu
Also Included In: Flu / Cold / SARS
Article Date: 19 May 2005 - 13:00 PDT

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Scientists from the World Health Organization are concerned that the bird flu virus in parts of northern Vietnam may be evolving. The fear is that the mutation could mean a virus that would much more easily be transmitted to humans, and from human-to-human.

Researchers say that there are some indications that the more dangerous, H5N1 virus could be evolving. They say that although they do not have conclusive proof, waiting until the proof arrives may be too late to prevent a pandemic from taking place. Nations need to move ahead as quickly as possible in order to prepare.

Some important epidemiological features of human H5N1 infections occurred in northern Viet Nam during January through April 2005 and appeared to differ in some respects from those seen in 2004 in other parts of Asia, and in the concurrent period in southern Viet Nam. These included an increase in the number of case clusters in the north compared with the south, a prolonged interval between the first and last cases in clusters, detection of sub-clinical infections, an expanded age range of cases and fewer fatal cases. Investigators were not able to prove that human-to-human transmission had occurred.

However they expressed concerns, which were shared by local clinicians, that the pattern of disease appeared to have changed in a manner consistent with this possibility.

These differences suggest that the epidemiology of H5N1 infections may be evolving in Asia. The changes in epidemiological patterns are consistent with the possibility that recently emerging H5N1 viruses may be more infectious for humans. Furthermore, sequencing analyses of H5N1 genes from avian and human H5N1 viruses from several countries suggest that they are becoming more antigenically diverse and may be forming distinguishable groupings based on phylogenetic analyses. CONTINUES...... WHO REPORT (PDF)

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