Pigs test positive for bird flu
Unconfirmed report suggests fatal strain of virus has managed to infect swine.
Chinese scientists say they have discovered a lethal form of avian influenza in pigs. If the findings are verified, a human pandemic may be closer than was previously thought.
So far, bird flu has claimed the lives of more than 25 people and 200 million birds in Asia. The fear is that if the virus has spread to swine, it may mutate into a lethal form that could easily spread to humans.
Speaking at a conference last week, Chen Hualan from China's Ministry of Agriculture said that the deadly strain of bird flu known as H5N1 was found in pigs at several Chinese farms in 2003 and 2004, including one in the Fujian province.
The World Health Organization (WHO) has yet to confirm the findings and is awaiting an official response from the Chinese authorities.
"If it has happened it is not that surprising," says WHO spokeswoman Maria Cheng, because other, less deadly strains of bird flu virus have been found in pigs before. The concern is that swine will act as a mixing vessel for the disease, she says.
If pigs harbour bird and human flu viruses at the same time, the two strains might, in theory, mix and share genes, creating a strain that could infect people directly. The disease would then be able to spread from person to person, something that it is not able to do so far.
Chen's team told the International Symposium on the Prevention and Control of SARS and Avian Flu in Beijing on 20 August that this is the first time the H5N1 strain has been found in pigs.
Even if the report is confirmed, it will be unclear until full details emerge whether the swine were actually infected with the virus, or whether they simply came into contact with it.
The same strain was found in nasal swabs taken from pigs in Vietnam earlier this year, but antibodies against the virus were absent. This suggests that pigs can come into contact with the virus without becoming infected.
The new allegation comes hot on the heels of three human deaths from bird flu that occurred in Vietnam at the beginning of August. The disease continues to beleaguer many parts of Asia and a recent outbreak in Malaysian poultry has prompted Singapore to ban all poultry imports from the country.
- Chen et al. Chinese J. Prev. Vet. Med., 26. (2004).