Wednesday, November 15, 2006

Experts identify key mutations in bird flu virus

Experts identify key mutations in bird flu virus
15 Nov 2006 18:00:26 GMT
Source: Reuters

HONG KONG, Nov 16 (Reuters) - A group of scientists has discovered two spots on the H5N1 bird flu virus that need to mutate for the virus to infect people more easily.

The virus has surface proteins that bind more easily to "receptors" lining respiratory tracts of birds, rather than receptors in humans. This means it easily causes disease in animals such as poultry but is much harder for humans to be infected.

But experts fear the H5N1 virus will infect more humans and trigger a pandemic killing millions of people if it mutates to attach easily to human receptors.

In the latest issue of Nature, scientists in Japan, Britain and the United States say they have discovered two specific spots on the genes of the virus that appear to determine if it attaches more easily to bird or human receptors.

This discovery will help scientists determine if any strain of H5N1 has the potential to cause a human pandemic. There are a number of strains now circulating across large areas of the globe.

"The bottomline is that the changes (on the two spots) can be used as molecular markers to identify the potential of the viruses that may grow well in humans," said Yoshihiro Kawaoka of the Institute of Medical Science at the University of Tokyo.

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.

"We found many mutations and we tried to identify which mutations were important ... two appeared to be very important (in the virus infecting a human)," Kawaoka told Reuters by telephone from the United States.

He warned against any over-emphasis on these two spots.

"It is very important that we shouldn't only focus on these two. The virus can become human-like by many mutations, these two are important but they are not the only ones," he said.

"But these two will give indication when a virus has changed receptor specificity," he said.

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