At the request of the Singapore government, World Health Organization (WHO) experts in laboratory safety will visit the country from Australia and Japan this weekend. They will investigate the origin of this week's reported new case of severe acute respiratory syndrome (SARS), which occurred in a laboratory worker. Experts from the US Centers for Disease Control (CDC) have also been invited.

The patient, a 27-year-old Chinese Singaporean postdoctoral student studying West Nile virus, had been working in laboratories at the National University of Singapore (NUS) and at the Singapore Environmental Health Institute (EHI), a division of the National Environment Agency. The case seems isolated, although 25 contacts are in quarantine for two incubation periods, which will end on September 22.

The student had no contact with other known SARS cases, but John Mackenzie, professor of microbiology at the University of Queensland, now seconded to WHO in Geneva for 5 months to coordinate downstream research on SARS, told The Scientist, "We understand he worked in the EHI on samples of West Nile virus, in a biosafety level 3 laboratory where they also worked on SARS. That's the only connection [to the live virus] we have at present."

Researchers at NUS also worked on SARS, but only on killed coronavirus. Nevertheless, the WHO experts will study both the NUS and EHI laboratories.

Mackenzie told The Scientist he believed there should be stronger regulations covering laboratory use of the SARS coronavirus, "but at the same time it's very difficult to police outside certain countries. In the US, Europe, and Australia, for example, we have very strict regulations. In many parts of Asia you don't, and there are lower containment levels."

But Wang Nan Chee, director-general of public health at the National Environment Agency expressed doubts that the EHI laboratory could be the source. He told Singapore's New Straits Times that none of the EHI's staff was unwell and that all had tested negative for SARS. He also claimed that the laboratory was well designed and followed WHO and CDC guidelines.