This study showed we should expect clusters of transmission, and that enhanced surveillance and contact tracing are essential to minimize it.

This case series gathered epidemiological and clinical data from individuals with confirmed COVID-19 from 3 clusters of COVID-19 linked to a tour group from China, a company conference, and a church.

As of Feb 15, 2020, 36 cases of COVID-19 were linked to the first three clusters of local transmission in Singapore. They identified 425 close contacts and quarantined them. The median incubation period was 4 days. The interval between transmission pairs ranged from 3-8 days.

SARS-CoV-2 is transmissible in community settings, and local clusters of COVID-19 are expected in countries with high travel volume from China before the lockdown of Wuhan and institution of travel restrictions. Enhanced surveillance and contact tracing are essential to minimize the risk of widespread transmission in the community.