Bird flu 'may pass to humans'
Updated on 17 May 2005
Scientists are warning that the virus which causes bird flu could soon be able to pass between humans.
The bird flu killed more than 50 people in Asia.
New evidence seen by Channel 4 News points to an increased risk of a global flu outbreak because of the way the virus has started to mutate.
It has killed 52 people in Asia in the last two years, and despite the slaughter of millions of birds has not stopped spreading. Now we've seen a report by World Health Organisation scientists which warns that the risk of a global flu outbreak is increasing.
These are the first signs the bird flu virus H5N1 is evolving and evolving in ways that make a global pandemic more likely.
Deep in northern Vietnam, scientists have noticed localised changes in the patterns of infection.
In the lab, they have seen genetic changes too that suggest the virus in northern Vietnam is different: changes that may affect how the disease will spread.
Scientists at the World Health Organisation monitoring avian flu in South East Asia say they are seeing what they call a "worrisome development".
Recent cases have started appearing in clusters and the disease is getting a little milder - signs, they say, the virus may be adapting to humans: changing genetically to transmit more easily between people at the cost of losing a little of its virulence.
Professor Maria Zambon from the Health Protection Agency, told Channel 4 News: ?If you have a virus which is more virulent for humans it may be less transmissable. But if the virus is better able to transmit within humans it may be less virulent.?
Even a weakened H5N1 virus will still be very dangerous. A flu virus infects human cells when a protein spike on the virus binds with a receptor on the cell surface.
The bird flu killed more than 50 people in Asia.
The genetic changes they have seen in the northern Vietnam viruses are in the gene that codes for the spike, a molecule called haemaglutinin, in a part that controls how well the spike fits into the receptor.
The report we've seen recommends immediate steps should be taken to step up surveillance in countries where H5N1 is present and they say there's an urgent need for up-to-date information on the genetics of the virus.
Constant monitoring of virus from new victims is the key: the WHO denies reports south-east Asian countries have failed to provide samples - Vietnam alone has supplied over a hundred - but it does admit it's been hard to extract virus from many of them, hampering research.
H5N1 is proving to be a virus full of surprises. The original jump from wild ducks - where it doesn't cause illness - to domestic chickens where it kills - was a genetic leap akin to a jump from a cat to a horse. The leap from chickens to humans was even bigger.
The nastiest surprise would be what's called reassortment - if a completely new virus emerged after H5N1 got into someone already infected with conventional human flu.
So news today three pigs in Indonesia have tested positive for H5N1 is a warning. There aren't many pigs in this largely Muslim country, but as a precaution pigs are being quarantined and tested before they're slaughtered.
And the news there are signs of genetic shifts in the virus in northern Vietnam could affect the plans of some governments to control a pandemic with vaccines.
Many that are now being stockpiled are based on British research that took a virus from Vietnam last year and genetically engineered to make it safe. The man who did it admits genetic shifts since then could make the stockpiles redundant.
One final surprise too. One recent sample from Vietnam proved to be, in part, resistant to the drug mainly used to treat victims of H5N1.
Chances are it's a one-off - the patient was being treated with the drug - but the WHO scientists warn that if further samples are found, it would have serious implications indeed.
