Severe acute respiratory syndrome: overview with an emphasis on the Toronto experience

To provide an overview of the severe acute respiratory syndrome (SARS) outbreak in Toronto, Ontario, which experienced the largest outbreak outside Asia, and to review what has been learned during the past year.

MEDLINE search of all studies related to SARS, including review of the Centers for Disease Control and Prevention, World Health Organization (WHO), and Health Canada Web sites.

During the SARS outbreak in Toronto, 438 people had been diagnosed as having suspected or probable SARS and 44 people died. Elderly people and those with comorbid illnesses were at greatest risk of complications or death. Transmission was via direct contact with respiratory secretions. The use of gloves, gowns, N95 masks, and eye protection was effective in preventing transmission. No transmission occurred before symptom onset or after recovery. Serologic tests suggest that antibodies may not appear until 28 days after illness onset. Molecular tests give their greatest yield during the second week of illness. The value of ribavirin treatment remains questionable. The combination of interferon plus corticosteroids appears to be better than corticosteroids alone. Postmortem examination revealed pulmonary edema and evidence of diffuse alveolar damage. Very few morphological changes were noted in other organs despite the presence of viral RNA as detected by polymerase chain reaction.

On July 5, 2003, the WHO declared that the SARS outbreak was over. Since then, new cases of SARS have been reported in Asia. With global travel, the disease can rapidly spread throughout the world. Therefore, we must remain vigilant to prevent another pandemic.