Five days after Canadian authorities ruled out severe acute respiratory syndrome (SARS) in an outbreak of respiratory infections in a British Columbia nursing home, questions remain about what exactly has sickened more than 140 patients and employees there. The Canadian researchers who first raised the alarm about a SARS connection (ScienceNOW, 21 August) stand by their findings, and they speculate that a hybrid between the SARS coronavirus and another agent may be involved in the outbreak.
With mild, coldlike symptoms, the outbreak in the Kinsmen Place Lodge in Surrey, British Columbia, never much looked like the severe, highly lethal disease that erupted from Asia last spring. And on 22 August, researchers at the British Columbia Centre for Disease Control and the BC Cancer Agency's Genome Sciences Centre announced that researchers had found in patients chunks of viral RNA, some 1000 base pairs in total, that closely matched the genome of OC43, one of two coronaviruses long known to cause common colds. OC43 is only distantly related to the SARS virus. The World Health Organization (WHO) has endorsed the conclusion that SARS is not involved.
But more alarming findings have come from researchers in Canada's flagship National Microbiology Laboratory (NML) in Winnipeg. NML Director Frank Plummer says his researchers have found some 1000 base pairs of viral RNA in patients that exactly match certain portions of the SARS coronavirus; they have also found SARS antibodies in patients. Plummer acknowledges that the symptoms don't match those of SARS; one explanation is that a hybrid virus is involved, he says. Others have speculated that a mutation tamed the SARS virus. Another possibility is that the NML findings are false positives--although Plummer says this is very unlikely.
The riddle could be solved if the virus's entire genome was sequenced, but so far, researchers have been unable to grow it. Meanwhile, the NML findings raise many questions; for instance, how much of a threat is a weakened SARS virus or a hybrid with OC43?
For now, health authorities have dropped the strict isolation measures appropriate for SARS. Whatever the virus is, says provincial health officer Perry Kendall, "it hasn't done anything nasty." Keeping up the extreme vigilance required for SARS during every respiratory outbreak would be like "putting an ambulance at every street corner."