Fig. 2

Definitions of contacts. Household-based contacts include the index case’s immediate and extended households defined by dwelling. History-based contact tracing relies on active contact tracing for the preceding 2 days, including household (close) contacts and community (casual) contacts. The immediate household consists of the index case’s place of residence at the time of diagnosis. The extended household comprises the index case’s immediate household in addition to their other dwellings (i.e., core, regular and on/off)