This article identifies the chief factors which transform a group of people into a “community of fate”. A community of fate refers to a temporary form of existence, born of duress and social emergency, which cuts across familiar divisions to elicit something socially consequential. One such community materialized during the 2003 Severe Acute Respiratory Syndrome (SARS) outbreak in Hong Kong. It is examined here in detail together with a range of other crisis communities – from Montreal battling smallpox, to the captives of the Warsaw Ghetto.