A study investigated all the clinical and epidemiologic data of the 243 confirmed Covid-19 cases in Singapore between January 23 and March 16, 2020. Clinical data included clinical histories before, during, and after the first positive SARS-CoV-2 test. Epidemiologic data included the activity history during the two weeks preceding symptom onset to ascertain possible sources of infection and contact tracing records. Instances of likely presymptomatic transmission were identified by making sure cases that were epidemiologically linked (clusters) had clear contact between a source patient and a patient infected by the source (a secondary patient), had no other likely explanations for infection, and had the source patient’s date of symptom onset occurring after the date of exposure to the secondary patient who was subsequently infected. Seven clusters were identified as likely presymptomatic transmission occurences, with a total of 10 cases attributed to presymptomatic transmission.

Presymptomatic Transmission of SARS-CoV-2 — Singapore, January 23–March 16, 2020

Smith College

- China
- Germany
- Japan
- USA
- Singapore

Asymptomatic COVID-19 Infection Categorized by Country

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