Temporal Dynamics of Viral Load and False negative Rate Influence the Levels of Testing Necessary to Combat COVID19 Spread

Jarvis, Katherine F.; Kelley, Joshua B.

Many colleges and other organizations are considering testing plans to return to operation as the COVID19 pandemic continues. The temporal dynamics of viral load and test false negative rate have the potential to alter the apparent efficacy of testing, as testing must identify a sick individual prior to that person transmitting the virus to one or more people and isolate them. High levels of presymptomatic spread and high false negative rates for testing make it difficult to successfully test an individual in the time frame necessary to stop viral spread. Here, we develop a stochastic agent-based model of COVID19 in a university sized population, considering the dynamics of both viral load and false negative rate of tests on the ability of testing to combat viral spread. We find that the undetectable period of SARS-CoV-2 can lead to an apparent false negative rate of ~17% in the presence of a hypothetical perfect test, while full implementation of dynamic false negative rates reported in the literature leads to an overall false negative rate of ~48%. We then compare testing while varying fraction of the population and the frequency of testing. We find that these assumptions about viral load and false negative rate lead to a requirement for high levels of both frequency and fraction of population tested in order to bring the apparent Reproduction number (Rt) below 1. We conclude that it is important to consider the non-uniform dynamics of viral spread and false negative rate in order to produce realistic testing plans that will lead to the desired reduction in Rt to control viral spread.