Estimating Preventable COVID19 Infections Related to Elective Outpatient Surgery in Washington State: A Quantitative Model

Yuemei Zhang; Sheng-Ru Cheng

is the (which was not peer-reviewed) The copyright holder for this preprint . https://doi.org/10.1101/2020.03. 18.20037952 doi: medRxiv preprint In other words, if someone is symptomatic and confirmed to be COVID19+ on any of the days between t+1 to t+4, then s/he was infected but asymptomatic on day t. Using data for Washington through March 17, 2020, we were able to calculate that there were at least 447 asymptomatic cases on March 13, 2020. However, this likely underestimates the actual prevalence of asymptomatic cases because this only includes the infected individuals that eventually tested positive, excluding those who ultimately never developed symptoms or only developed mild symptoms, those who developed severe symptoms but were never tested, and those who were tested but had a false negative result. Furthermore, the number of COVID-19 infections in the US and in WA have been steadily increasing over time. 2, 3 News reports that the virus is thought to have been circulating within communities for weeks prior to the outbreak also support the idea that this number underestimates the actual prevalence of asymptomatic cases. 26 Next, we needed to determine the ratio of asymptomatic uninfected people to uninfected people in the general population. We subtracted the confirmed infections on March 13, 2020 and the asymptomatic infected population on that day from the total population of WA in order to determine the uninfected population.