Migratory wild birds from China, which were found to have contracted bird flu from poultry, could potentially spread the disease to Europe, as well as Australia, Chinese scientists report.
At least 6,000 wild birds at Qinghai Lake in north-west China - a popular summer destination for migrating fowl - have died after being infected with a bird flu virus (H5N1), also known as avian influenza, that is closely related to the one that laid waste to poultry farms across southeast Asia.
Some of the thousands of potentially infected birds could carry the virus to India, Europe and Australia, the two teams of Chinese scientists who conducted the study warned in Nature and Science. This may occur as the survivors start returning to their winter ranges which stretch from eastern Europe to Alaska and Australia.
“Our findings indicate that H5N1 (bird flu) viruses are now being transmitted between migratory birds at the lake,” the Joint Influenza Research Centre of the Shantou University Medical College and the University of Hong Kong said in its study.
“There is a danger that it might be carried along the birds’ winter migration routes to densely populated areas in the south Asian sub-continent, a region that seems relatively free of this virus, and spread along migratory flyways linked to Europe.”
Whether the virus spreads or not depends, the researchers explain, on whether any infected birds remain healthy enough to migrate - which is far from clear. “We have had no chance to sample healthy migratory birds by Qinghai Lake,” says Yi Guan at Shantou University Medical College, who led one of the teams. The researchers would like to explore this likelihood but are awaiting permission from the Chinese ministry of agriculture, which is reportedly planning to investigate later in July.
Part of the H5N1 virus is closely related to one isolated from a chicken in Shantou in 2003. Another part resembles viruses found in southern China earlier in 2005, which belong to the ‘Z genotype’ virus circulating across east Asia.
If the Qinghai virus spreads to other countries, it is almost certain that it will devastate the poultry industries there. However, scientists do not know if it could kill humans. It does have a mutation linked to increased deadliness in mammals: one of the Chinese teams found that it kills all mice infected with it in four days. However, this mutation may not be enough to make it deadly to humans.
It also appears that H5N1 viruses in Asia are swapping genes - which could give rise to a virus capable of causing a human pandemic. The World Health Organisation (WHO) estimates that there is a chance that the bird flu virus may mutate into a form leading to a pandemic, such as the Spanish flu outbreak in 1918 that killed 25 million people. However, modern medicine will more than likely lower the death toll.
To date, the WHO reports that there have been 108 confirmed human cases of bird flu of which 54 have been fatal.