In a new study entitled, "Post-lockdown SARS-CoV-2 nucleic acid screening in nearly ten million residents of Wuhan, China," the findings appear to be good news from the standpoint of asymptomatic spread and length of immunity after infection.
According to the study, more than 9.8 million Wuhan, China residents (where COVID-19 is believed to have originated) underwent testing between May 14 and June 1 to measure the infection rate in the community.
Among the findings:
- 9,865,404 participants who had not previously contracted COVID-19 were not infected at the time of testing.
- 300 people tested positive but had no symptoms (asymptomatic).
- 1,174 close contacts of the asymptomatic patients all tested negative for coronavirus.
- There were 34,424 recovered coronavirus cases.
- Among them, 107 tested positive again (.310%) but "virus cultures were negative for all asymptomatic positive and repositive cases, indicating no 'viable virus' in positive cases detected in this study."
The following is the study abstract:
Stringent COVID-19 control measures were imposed in Wuhan between January 23 and April 8, 2020. Estimates of the prevalence of infection following the release of restrictions could inform post-lockdown pandemic management. Here, we describe a city-wide SARS-CoV-2 nucleic acid screening programme between May 14 and June 1, 2020 in Wuhan. All city residents aged six years or older were eligible and 9,899,828 (92.9%) participated. No new symptomatic cases and 300 asymptomatic cases (detection rate 0.303/10,000, 95% CI 0.270–0.339/10,000) were identified. There were no positive tests amongst 1,174 close contacts of asymptomatic cases. 107 of 34,424 previously recovered COVID-19 patients tested positive again (re-positive rate 0.31%, 95% CI 0.423–0.574%). The prevalence of SARS-CoV-2 infection in Wuhan was therefore very low five to eight weeks after the end of lockdown.
Read the full study findings here: