Volume 26, Number 7—July 2020
Evidence Supporting Transmission of Severe Acute Respiratory Syndrome Coronavirus 2 While Presymptomatic or Asymptomatic
|Reference||Setting||Patient(s), age/sex||Laboratory findings||Limitations|
||Nursing home outbreak in Washington
||24 presymptomatic and 3 asymptomatic
||Mean RT-PCR Ct value 24.2 for presymptomatic and 27.3 for asymptomatic patients. Viral culture identified infectious virus in 7 (64%) of 11 specimens from presymptomatic patients; no virus detected in 1 asymptomatic patient.
||Incomplete viral culture sampling from all presymptomatic and asymptomatic patients.
||Repatriated to Germany from Wuhan, China
||2 asymptomatic adults
||Patients’ RT-PCR Ct values 24 and 30; infectious virus was detected by viral culture for both.
||No evidence of transmission during evacuation flight.
||Family cluster in Singapore
||Asymptomatic 6 mo/M
||RT-PCR Ct values 14 at diagnosis and increased to 33 over 9 d.
||No evidence of transmission from the infant to another household member.
||Cluster in Vietnam related to travel to Wuhan
||Asymptomatic 55 y/M
||RT-PCR Ct values >40 at diagnosis and during 9 d of viral RNA shedding.
||High Ct in the asymptomatic patient suggests minimal infectiousness.
|(27)||Family cluster in Guangdong, China||Asymptomatic, 26 y/M||RT-PCR Ct values 22–32 during testing 7–11 d after initial diagnosis.||No evidence of transmission to other family members in the cluster.|
*Ct, cycle threshold, RT-PCR, reverse transcription PCR.
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