Scientists find key to mutations in bird flu virus

Nov 16 2006

An international group of scientists say they have found two spots on the H5N1 bird flu virus that will need to mutate for the virus to infect people more easily.

The scientists from Japan, Britain and the United States say the two specific spots on the genes of the virus appear to determine if it attaches more easily to bird or human receptors.

It seems the virus has a surface protein called haemaggluttinin, that binds more easily to "receptors" lining respiratory tracts of birds, rather than receptors in humans, which effectively means that it easily causes disease in animals such as poultry, but is much harder for humans to be infected.

However the experts fear the H5N1 virus, if it mutates to attach easily to human receptors, will infect more humans and trigger a pandemic which could kill millions of people.

The discovery of the two spots will enable scientists to determine if any strain of H5N1 has the potential to cause a human pandemic.

There are currently a number of strains now circulating across large areas of the globe.

Yoshihiro Kawaoka of the Institute of Medical Science at the University of Tokyo, says the spots can be used as molecular markers to identify the potential of the viruses that may grow well in humans.

By using 21 samples of the H5N1 virus taken from human victims in Indonesia and Vietnam, the team of scientists found that three of them bound especially easily to human receptors.

Kawaoka says they have found many mutations but tried to identify which mutations were important and these two particular spots appeared to be very important in regard to the virus infecting a human.

He does however caution against any over-emphasis on the two spots as the virus can become human-like by many mutations, and though these two are important, they are not the only ones.

The work shows that at least two changes are needed for H5N1 to transform to strain that could infect humans.

To date, according to the World Health Organization, there have been a total of 258 cases of H5N1 in humans, and 153 deaths.

The research is published in the journal Nature.