The World Health Organization today acknowledged that a 27-year-old man in Singapore has likely been infected with the severe acute respiratory syndrome (SARS) coronavirus, the first infection documented since WHO declared the disease under worldwide control in early July. The case is puzzling. Although several laboratory tests have indicated that the man is infected with the virus, he suffered only a mild fever and cough, and has now fully recovered. More than 2 dozen of the man's contacts have been quarantined, but officials say the case does not seem to threaten public health.
SARS wreaked havoc this spring when the newly identified virus infected more than 8000 people worldwide and disrupted travel and commerce. In July, WHO declared that the disease was under control and that all known chains of transmission had been broken. But scientists have been bracing for a possible return of the virus during this winter's cold and flu season.
The new patient is a postdoctoral researcher who studies West Nile virus. He first came down with a fever on 26 August, several days after working in a biosafety level 3 lab that had previously been used to study the SARS coronavirus. Because the man has had no contact with known SARS patients, investigators are carefully checking to see if the infection resulted from a lab accident.
The man's mild symptoms do not meet the clinical definition of SARS, says Klaus Stöhr, who coordinated WHO's response to the outbreak last spring. However, he says, multiple polymerase chain reaction (PCR) tests have turned up positive for the coronavirus, and blood tests show that the man's production of antibodies against the virus have increased. Those tests "fulfill the laboratory definition of a case," he says, "but because the case is so strange it really deserves some additional verification." None of the man's contacts have shown any sign of SARS symptoms, Stöhr says.
Researchers are especially wary of jumping to conclusions about new SARS outbreaks after a recent false alarm in British Columbia. Officials there worried that a cluster of respiratory infections in a nursing home could be a SARS outbreak, but the illness turned out to be caused by a different virus (ScienceNOW 27 August).
Singapore's quarantine measures are prudent steps to prevent SARS from reemerging, Stöhr says. Because there is not yet a rapid and definitive test for the disease, "it is not unlikely" that new SARS cases could slip through the available detection mechanisms, he says. Nevertheless, the success at curbing SARS earlier this year leaves Stöhr feeling hopeful that any future outbreak can be controlled.