Editorial Commentary: Crouching Tiger, Hidden Dragon: The Laboratory Diagnosis of Severe Acute Respiratory Syndrome

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Abstract
While the world awaited the next influenza pandemic to emerge from southern China, “nature,” as always, caught us by surprise. The unusual “atypical” pneumonia, subsequently called “severe acute respiratory syndrome” (SARS), that emerged out of southern China in late 2002 was not caused by influenza, but was, in fact, caused by a novel coronavirus [ 1–3]. Epidemiologically, infection with the SARS coronavirus (SARS-CoV) is closely linked with SARS [ 1, 4], and experimental infection of cynomolgus macaques (Macaca fascicularis) results in pathology reminiscent of the human disease [ 4, 5]. Human coronaviruses 229E and OC43 are known to be causes of the common cold and have received scant attention, either diagnostically or research wise, in the past few decades. Coronaviruses also cause disease in animals that varies from transmissible gastroenteritis in pigs, to feline infectious peritonitis in cats, to avian infectious bronchitis in chickens. However, phylogenetic relationships suggested that this new virus was not closely related to any of the previously known human or animal coronaviruses and that SARS-CoV may, in fact, be the first representative of a new group within the coronavirus family [ 6, 7]. The lack of serological evidence of prior SARS-CoV infection in the healthy population in many parts of the world, including regions where the disease outbreaks were the most severe, suggested that this was a virus that had recently entered the human population, presumably from an animal reservoir [ 1, 8]. Although the animal reservoir in nature remains to be defined, the recent isolation of SARS-CoV–like virus from small mammals in live wild-game animal markets in southern China confirmed the zoonotic origin of the virus and suggested that these markets could potentially be the interface where the inter-species jump from animals to humans occurs [ 9].