acute respiratory syndrome: the Toronto experience

In February 2003 the worldwide outbreak of severe acuterespiratory syndrome (SARS) reached Toronto. Thisfirst phase of the outbreak, lasting from March to May 2003, resulted in 257 probable and suspect cases and 27 deaths. Shortly after apparent containment of this outbreak, a second phase occurred, from May to June 2003, with an additional 119 probable and suspect cases and 17 deaths.1 Early in the outbreak, the search for the etiologic agent of SARS revealed a new coronavirus.2–4 Laboratory investi-gations in Canada added evidence that SARS cases in this country were associated with this new coronavirus.5 The rapid sequencing of the SARS-associated coronavirus (SARS-CoV) genome by 2 independent research groups enhanced the development of new molecular assays by vari-ous laboratories around the world.6,7 Reverse-transcriptase polymerase chain reaction (RT-PCR) tests, primarily tar-geting the polymerase gene of the virus, were developed, along with serologic tests for antibodies against the newly discovered SARS-CoV. Although these tests were made available during the outbreak, their sensitivity and speci-ficity were unknown because there were no “gold standard” laboratory or clinical definitions for the diagnosis of SARS. The formal disease definitions developed by the Worl