Lai CKC, Ng RWY, Wong MCS, et al. - Researchers sought to inscribe the epidemic curve, incidence, clusters, reproduction number (Rt), incubation period and time to containment of the coronavirus disease 2019 (COVID-19) in Hong Kong (HK) via conducting an epidemiological study using government information covering the first 100 confirmed cases. Of these cases, 93 were HK residents (6 infected in Mainland China, 10 on the Diamond Princess Cruise) and seven were visitors infected in Mainland China before entering HK. The cases, in majority (76%), were aged ≥ 45 years; increase in the incidence was observed with age. The importation and transmission of COVID-19 in HK reduced with timely stringent containment policies. A reduction in the proportion (62.5% to 0%) of cases imported from Mainland China, and a decrease in Rt (1.07 to 0.75) occurred in correlation with escalation of border control measures. The median incubation period of 4.2 days was observed. Households involving 2–4 people formed most clusters with identifiable epidemiological links. They identified three medium-spreading events: two from New Year gatherings (6–11 people), and another from environmental contamination of a worship hall (12 people). Containment delay was evident in 78.9% of cases despite intensified contact tracing. In a multi-storey building, there was suspicion of an unusual transmission via faulty toilet plumbing leading to evacuation of > 100 residents overnight. Per analysis, faulty plumbing was unlikely to be the source of this transmission.