SARS: UN health agency clears Toronto after 20 days without transmission

The United Nations health agency today removed Toronto, Canada, from its list of areas with recent local transmission of SARS, leaving Taiwan Province as the only region in the world still to have experienced recent local transmission of Severe Acute Respiratory Syndrome.

“This is a great achievement for public health in what we hope is the final phase of the global emergency,” the World Health Organization (WHO) Executive Director for communicable diseases, David Heymann said. “Toronto faced an especially challenging outbreak. As we have learned, SARS is a difficult disease that produces many surprises and setbacks.”

Since it first emerged in China’s Guangdong province, SARS has infected 8,445 people, killing 812, most of them in China. Canada with 252 cases and 192 deaths registered the largest toll outside China and its various regions. The last probable case in Toronto was detected on 12 June and immediately isolated. When 20 days, or twice the incubation period, have passed without detection of a new case, the chain of human-to-human transmission is considered broken.

“We should all pay tribute to the health workers and others in Canada who had their lives disrupted and threatened by this disease,” Dr. Heymann said. “When the virus returned to start a second outbreak, health workers continued the fight and have now won it. We also need to remember the commitment of Canada’s scientists, who rapidly provided information about the virus and its epidemiology that has benefited public health around the world.”

Toronto was among the first areas affected after the virus moved out of southern China in late February, and began to spread internationally. WHO said that if no further cases are reported in Taiwan Province, that region too will be removed from the list later this week and SARS will be declared to have broken the chain of person-to-person transmission.

From the outset, WHO’s objective in combating SARS has been to seal off opportunities for the disease to become established in its new human host. Interruption of human transmission will be a milestone on the way to achieving this goal. But scientists cannot at present guarantee that SARS has been vanquished, as questions remain about the origins of the virus and its possible seasonal occurrence. In addition, transmission may be occurring somewhere in the world at such a low level as to defy detection.