SARS Cases in Asia Show Labs' Risks

In the wake of the SARS epidemic, WHO recommended that the virus be handled only in laboratories rated "biosafety level 3," or "BSL-3." Such labs limit access, and their workers must handle microbes in sealed or vented cabinets and wear protective clothing. Only BSL-4 labs, where technicians and scientists must wear spacesuits that have their own air supply, are more restrictive.

BSL-4 labs, however, are rare and expensive to operate. The United States has four. SARS was designated a BSL-3 pathogen in part for practical reasons.

"We put the virus at a level appropriate to avoid its accidental release, but also at a level at which enough work could be done on it. If we'd put it on Level 4, it would restrict it to just a handful of laboratories worldwide," said John Mackenzie, a scientist at Curtin University of Technology in Australia, who helped formulate the WHO guidelines.

The three SARS lab outbreaks appear to have had distinct causes.

In Singapore in September, a sample of West Nile virus contaminated with SARS virus infected a 27-year-old lab worker at the Environmental Health Institute. The lab was not known to have stocks of SARS, but it had been pressed into service during the epidemic, which is presumably when the contamination occurred. Although the lab claimed a BSL-3 rating, a WHO inspection team found it did not meet those standards.

The Taiwan case happened in a BSL-4 lab when a 44-year-old military scientist failed to follow procedures in cleaning up a spill of SARS-containing fluid. It was judged to be a case of individual carelessness or a failure of training.

The Beijing case is the most mysterious and troubling. There, a 26-year-old graduate student developed SARS in late March, just two weeks after she started working at the virology institute. In mid-April, a 31-year-old man in the same lab also came down with the disease. Neither had been working with the SARS virus.

The graduate student went home to Anhui province, where she infected her mother, who died. The student then became ill enough to be hospitalized and infected a nurse. The nurse, in turn, infected five others -- three relatives, a patient and a relative of that patient -- in a "third generation" of infection. When the outbreak became known, Taiwan and Australia instituted health alerts, screening visitors from China or ordering special surveillance of recent travelers who became ill.

What the latest accident "has done beyond a shadow of a doubt is show that we do need some international agreement as to what a Biocontainment Level 3 lab is," Mackenzie said. "Unless everyone has the same standards, we may be talking about chalk and cheese." He said he and several others are calling for an international system to "accredit the laboratories and accredit the training of the people working in them."

Larry Anderson, chief of respiratory pathogens at the Centers for Disease Control and Prevention, said safe handling of SARS requires the right lab design, personal equipment, adequate training of workers, proper technique and medical surveillance of people at risk of exposure. Since the virus emerged, the CDC has distributed samples of it to 56 laboratories at universities, government departments and companies. Fourteen are overseas. Anderson would not name any of them and said he does not think the large number is inherently unsafe.