Characterization of an Asymptomatic Cohort of Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) Infected Individuals Outside of Wuhan, China

Clin Infect Dis. 2020 Nov 19;71(16):2132-2138. doi: 10.1093/cid/ciaa629.


Purpose: We aimed to further clarify the epidemiological and clinical characteristics of asymptomatic severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections.

Methods: We identified close contacts of confirmed coronavirus disease 2019 (COVID-19) cases in northeast Chongqing, China, who were confirmed by real-time reverse transcription polymerase chain reaction-positive (RT-PCR+). We stratified this cohort by normal vs abnormal findings on chest computed tomography (CT) and compared the strata regarding comorbidities, demographics, laboratory findings, viral transmission and other factors.

Results: Between January 2020 and March 2020, we identified and hospitalized 279 RT-PCR+ contacts of COVID-19 patients. 63 (23%) remained asymptomatic until discharge; 29 had abnormal and 34 had normal chest CT findings. The mean cohort age was 39.3 years, and 87.3% had no comorbidities. Mean time to diagnosis after close contact with a COVID-19 index patient was 16.0 days, and it was 13.4 days and 18.7 days for those with abnormal and normal CT findings, respectively (P < .05). Nine patients (14.3%) transmitted the virus to others; 4 and 5 were in the abnormal and normal CT strata, respectively. The median length of time for nucleic acid to turn negative was 13 days compared with 10.4 days in those with normal chest CT scans (P < .05).

Conclusions: A portion of asymptomatic individuals were capable of transmitting the virus to others. Given the frequency and potential infectiousness of asymptomatic infections, testing of traced contacts is essential. Studies of the impact of treatment of asymptomatic RT-PCR+ individuals on disease progression and transmission should be undertaken.

Keywords: COVID-19; SARS-CoV-2; asymptomatic infection; characterization.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Aged
  • Aged, 80 and over
  • COVID-19 / epidemiology*
  • China / epidemiology
  • Female
  • Humans
  • Male
  • Middle Aged
  • Pandemics
  • Real-Time Polymerase Chain Reaction
  • Retrospective Studies
  • SARS-CoV-2 / pathogenicity*
  • Young Adult