HONG KONG, Mar 13 (Reuters) Experts are urging China to conduct random tests on live poultry in its retail markets after a study found that some apparently healthy chickens, ducks and geese were infected with the deadly H5N1 virus.
The calls follow the death of a man from H5N1 this month, who fell sick after visiting poultry markets in southern Guangdong province.
A Chinese disease expert has said the man might have caught the virus from infected birds showing no signs of the disease.
''We are mystified about the cause of the person who fell sick in Guangdong. We will be happy if Chinese authorities did more pro-active checking of apparently healthy chickens,'' said Peter Cordingley, a spokesman for the World Health Organisation.
Ten people in China have died from H5N1 so far, but most of the cases occurred in places where there were no reported H5N1 outbreaks or unusual deaths in birds, sparking fears that infected poultry without symptoms may be the culprits.
That theory seemed to gain credence after scientists in Hong Kong and China found that up to 1 per cent of apparently healthy chickens, ducks, geese and other poultry in wet markets across seven provinces in southern China were in fact carrying the virus.
China's Ministry of Agriculture declined immediate comment.
Asked about asymptomatic chickens in south China, Noureddin Mona, the Food and Agricultural Organisation's representative in Beijing, said: ''We have not got any confirmation from the ministry ... We will ask them to clarify this.'' DUBIOUS VACCINES? The finding is significant because people can no longer rely on signs of disease to tell if their flocks are infected, and they would be none the wiser if they were exposed to the virus. H5N1 infected chickens usually die within 24 hours.
''This is more dangerous. The chickens look healthy and happy but they pass the virus to us,'' said Lo Wing-lok, an infectious disease expert in Hong Kong who urged China to conduct random tests on healthy looking chickens in farms and markets.
At least 97 people have died in East Asia and the Middle East since late 2003 from H5N1 and most caught it direct from infected chickens. Experts fear the virus could mutate and become more easily transmitted among people, triggering a pandemic.
But Julian Tang, a microbiologist from the Chinese University in Hong Kong, called for calm.
''Nearly all these cases (97) could be linked to symptomatically infected birds. So, looking at these figures, there seems to be very little role in transmission of H5N1 from these asymptomatically-infected birds to humans to cause a symptomatic infection,'' Tang told Reuters.
The appearance of asymptomatic chickens in China, however, has raised questions about China-made vaccines.
''We're fairly certain that what is happening in southern China is that because of the mass vaccination policy that they have been carrying out, they now have chickens that look well but which are in fact infected,'' said a source familiar with the situation.
''These vaccines are not dedicated vaccines for H5N1. They don't directly blitz the virus. They could cause mishaps.
''We are on standby to see more (H5N1 human) cases across China ... it is not good enough just to wait for a chicken to fall over sideways and then do tests on it, you have to do pro-active tests on chickens.'' REUTERS SB BD1458