According to a study of ten million people published in November, asymptomatic transmission of COVID-19 did not occur at all.
The paper is titled “Post-lockdown SARS-CoV-2 nucleic acid screening in nearly ten million residents of Wuhan, China” and was published in the scientific journal Nature Communications. Approximately 10 million people were screened between May 14 and June 1, with researchers finding 300 asymptomatic cases. Testing of their 1,174 close contacts revealed 1,174 negative results, no positives, meaning that there was no asymptomatic transmission of COVID-19.
“The citywide nucleic acid screening of SARS-CoV-2 infection in Wuhan recruited nearly 10 million people, and found no newly confirmed cases with COVID-19. The detection rate of asymptomatic positive cases was very low, and there was no evidence of transmission from asymptomatic positive persons to traced close contacts. There were no asymptomatic positive cases in 96.4% of the residential communities,” the study reads.
Although an infected person can take a few days to develop symptoms, people who get infected and never develop symptoms “generally have low quantity of viral loads and a short duration of viral shedding, which decrease the transmission risk of SARS-CoV-2,” according to the study.
The results also remained the same after the asymptomatic individuals and their close contacts were placed in isolation for two weeks.
“None of [the] detected positive cases or their close contacts became symptomatic or newly confirmed with COVID-19 during the isolation period,” the study said.