Bird Flu — A Potential Pathway into Humans

A detailed look at the structure of one of the surface proteins of the H5N1 "bird flu" virus points toward a way that certain mutations could ease the H5N1 virus’ spread in the human population, according to a new study in the 17 March 2006 issue of the journal Science.

In a H5N1 virus sample isolated from a Vietnamese boy who died from the flu in 2004, James Stevens and colleagues determined the structure of the hemagglutinin protein, which allows the virus to enter host cells. Hemagglutinin latches on to different cell receptors in avian and human-type flu, which may explain why most bird flu viruses do not spread between humans.

There are a few known mutations that can convert H2 and H3 type bird flu viruses from a bird to human receptor preference, but Stevens and colleagues show that these mutations do not cause the H5 type bird flu virus to switch to a human receptor preference. However, the researchers say that some of these mutations may make the H5N1 hemagglutinin more likely to bind to a human-type receptor, providing a possible "foothold" for the virus in the human population.

Becky Ham

20 March 2006