The Innovation
ReportModeling the Prevalence of Asymptomatic COVID-19 Infections in the Chinese Mainland
Public Summary
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As entering a post-pandemic period, considerable efforts have been spent to intensify the screening of the asymptomatic COVID-19 infections by large-scale survey in the Chinese Mainland.
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However, only 0.8% and 3.3% asymptomatic cases in Wuhan City and Chinese Mainland developed into the symptomatic ones during this period, and the un-development ratios were up to 99.2% and 96.5% when assuming the developing lag = 5.2 days, respectively.
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A mathematical model based on the Bayes’ formula was established to predict the prevalence of asymptomatic cases in Chinese Mainland, which revealed a very low prevalence of asymptomatic infections.
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When the basal prevalence became lower, some false positive results would appear. Therefore, another immediate confirmation test is suggested to perform for asymptomatic screening during the post-pandemic period.
Summary
Recently, considerable efforts have been focused on intensifying the screening process for asymptomatic COVID-19 cases in the Chinese Mainland, especially for up to 10 million citizens living in Wuhan City by nucleic acid testing. However, a high percentage of domestic asymptomatic cases did not develop into symptomatic ones, which is abnormal and has drawn considerable public attention. Here, we aimed to investigate the prevalence of COVID-19 infections in the Chinese Mainland from a statistical perspective, as it is of referential significance for other regions. By conservatively assuming a development time lag from pre-symptomatic (i.e., referring to the infected cases that were screened before the COVID-19 symptom onset) to symptomatic as an incubation time of 5.2 days, our results indicated that 92.5% of those tested in Wuhan City, China, and 95.1% of those tested in the Chinese Mainland should have COVID-19 syndrome onset, which was extremely higher than their corresponding practical percentages of 0.8% and 3.3%, respectively. We propose that a certain false positive rate may exist if large-scale nucleic acid screening tests for asymptomatic cases are conducted in common communities with a low incidence rate. Despite adopting relatively high-sensitivity, high-specificity detection kits, we estimated a very low prevalence of COVID-19 infections, ranging from 10−6 to 10−4 in both Wuhan City and the Chinese Mainland. Thus, the prevalence rate of asymptomatic infections in China had been at a very low level. Furthermore, given the lower prevalence of the infection, close examination of the data for false positive results is necessary to minimize social and economic impacts.
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These authors contributed equally