Cluster B
On Feb 4, 2020, Malaysia confirmed a case of COVID-19 in an individual (B1) who had recent travel history to Singapore on Jan 16–23, 2020, for a company conference (a closed business meeting for employees from company branches globally), which was attended by at least 111 participants from 19 different countries on Jan 20–22, 2020. 17 attendees at the conference were from mainland China and at least one was from Wuhan. Subsequently, six participants at the conference who had no recent travel history to China (B2, B3, B4, B5, B6, and B7) tested positive for SARS-CoV-2 (figure 1 middle panels). Two affected individuals from Singapore were identified through contact tracing of participants after notification from the Malaysian International Health Regulation (IHR) focal point.
The conference programme included business presentations, workshops, breakout discussions, a welcome reception and meals, team-building games, and a Singapore city bus tour. Seating arrangements (where available) for the conference, and interviews with affected individuals, indicated close interactions between cases. Two groups (B1 and B3, and B4 and B7) were seated at the same tables for a 3-h Chinese banquet-style dinner on Jan 20, 2020, with three and two attendees from China, respectively. Four cases (B1, B3, B4, and B5) were in a 4-h breakout session on Jan 21, 2020, with 41 other participants, including ten from China, of whom three had dined with B1 and B3 or B4 and B7 at the Chinese banquet. Furthermore, the team-building games entailed close physical contact.
With initial news of B1, 15 conference participants remaining in Singapore were contacted to find out about their health status. Four people reported being unwell with fever, respiratory symptoms, or both and were tested for SARS-CoV-2; two individuals (B4 and B5) tested positive for the virus. The third local case (B6) was identified via activity mapping to have attended the conference and had subsequent interactions with company staff. 153 close contacts were placed under quarantine. Hotel staff were told to monitor their health status, and none reported being unwell during the conference or subsequently. 13 secondary cases of COVID-19 were reported among family members of B1 in Malaysia and contacts of B7 in France.