Researchers at the Beijing Genomics Institute of the Chinese Academy of Sciences have mounted a wide-ranging search of domestic and wild animals, in a hunt for coronaviruses similar to that which is thought to cause severe acute respiratory syndrome (SARS). The work is part of a broader international effort that is attempting to seal off potential reservoirs of future infection.

“Dozens of species have been tested,” says the institute's director, Henry Yang, although he declines to reveal which ones, and whether they have been found to be free of coronavirus. “If we said we haven't found anything yet in, say, chickens, people would rule out the chicken as the reservoir,” he says. “But that would be jumping the gun.”

The closest known relatives of the human SARS virus are coronaviruses from cows and birds, species that Yang says his group is treating as priorities. Coronaviruses have also been found in pigs, mice and cats. But the relationship between these animal viruses and the human SARS virus is relatively distant — so Yang also intends to look in other species, such as bats and monkeys, to see whether a closer relative can be found.

Meanwhile, other researchers are looking at the possibility that SARS is transmitted in blood — which would make blood banks potential reservoirs. As yet, they do not know whether the virus is present in the blood of symptomless carriers, although most consider this unlikely by extrapolation to other viral infections. Agencies such as the US Food and Drug Administration and the Frankfurt Blood Bank are looking at screening strategies to identify the virus, should it turn up in blood.