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The early days of the COVID-19 were ominously reminiscent of SARS. We had a mystery illness originating in China with an animal market link caused by a virus with a genetic similarity to the SARS coronavirus. Not surprisingly, the World Health Organization (WHO) and the Chinese deployed the strategy that worked with SARS: find the cases with alacrity, isolate them and monitor their immediate contacts for the development of disease. Isolate the contacts if they get sick. The strategy worked: SARS was contained and it never returned. SARS, though it killed 10 per cent of its victims, was not contagious enough to cause significant sustained community disease.

But can COVID-19 really be contained? COVID-19 stopped following the SARS script weeks ago and appears similar to many respiratory viruses. COVID-19, along with the four “common cold” coronaviruses, spread easily from person to person with mild disease, and sometimes from people before they develop symptoms. It is practically impossible to contain a virus that readily spreads early in the course of infection and circulates in the community. The highest concentration, and therefore transmissibility, of COVID-19 in nasal secretions peaks in the first few days of infection. SARS was different: it was transmitted most efficiently in the late stages of the infection. Therefore, using the SARS model to identify patients with the symptoms of COVID-19 is bound to fail. Moreover, it’s hard to pick out COVID-19 cases from those caused by other respiratory viruses also seen at this time of year. Testing and tracking down contacts is ultimately futile for this virus, as it devotes enormous resources to finding cases that are largely mild and spontaneously resolving.