Using the COVID-19 to influenza ratio to estimate the numbers of symptomatic COVID-19 cases in Wuhan prior to the lockdown.


A recent study tested 45 throat swabs taken from adults over age 30 who sought outpatient care at one of two central Wuhan hospitals for influenza-like-illness between December 30, 2019 and January 19, 2020. Although none were confirmed COVID-19 cases, nine retrospectively tested positive for the virus. Using the fact that Wuhan has 393 other hospitals, we extrapolate the total number of undetected cases of symptomatic COVID-19 in adults during this period. we estimate that there were 5,558 [95% CI: 2,761-9,864] adults with symptomatic COVID-19 infections in Wuhan between December 30th and January 19th, 2020.

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