Scientists have identified a new, unexpected suspect in their search to find the origin of SARS.
Since the severe acute respiratory syndrome (SARS) outbreak in 2002-03 that killed around 800 people, scientists have tested several species of animal for coronaviruses, viruses closely related to the SARS virus, that may have sparked the epidemic.
Now research by Chinese, Australian and American scientists indicates bats not masked civets, rats or badgers as had previously been suggested may be the original hosts, Xinhua reported on Friday.
Other mammals previously suspected were only "vectors," new research suggests. They became infected with the virus and passed it on, but were not the origin of the disease.
Even so, a prominent Chinese disease expert insists it is too early to say wild bats are the definitive natural host of the virus, adding that more research needs to be done. In the study, conducted last year, researchers trapped 408 bats at four locations around China: south China's Guangdong Province, the Guangxi Zhuang Autonomous Region, central China's Hubei Province and Tianjin Municipality in north China.
Researchers then collected bats' blood, fecal and throat swabs, and analyzed their serum samples alongside DNA from fecal or throat samples tested independently using different methods in laboratories in Wuhan, Hubei's capital, and Geelong, Australia.
The coronaviruses found in bat samples were genetically diverse, but all showed some similarity to the SARS coronavirus that triggered the 2002-3 pandemic, said Li Wendong, a researcher from the Chinese Academy of Sciences.
The genetic similarity between the bat virus strain and the SARS coronavirus was a 92 per cent match, the report said, leading researchers to their new premise.
"The current report only raises a hypothesis that the bats might be the source of the virus," said Liu Qiyong, an expert in diseases from the Chinese Center for Disease Control and Prevention.
In further research, at least two things must be proved, Liu said. One is how the virus carried by bats developed into the SARS virus.
"The 92 per cent similarity may mean nothing and does not prove the bat was the original host. Even if two viruses are more than 99 per cent similar to each other, we still cannot say that they have a host relationship," Liu said. What's more, even if the virus carried by the bats is 92 per cent similar to the SARS virus, it can also develop into other kinds of viruses, Liu noted.
The second point is "proving how the virus came to the civets or other middle hosts and then to human beings," Liu added.
The new findings have been published in the online edition of the journal Science.
Bats are hosts of several other known viruses but rarely display clinical symptoms, Liu said. They are also increasingly present at food and traditional medicine markets in southern China and elsewhere in Asia.
(China Daily October 2, 2005)