Percentage of reported Covid-19 cases in Colombia: Estimating the true scale of the pandemic

Abstract

Since March 6, when Colombia confirmed its first case of the coronavirus disease (Covid-19), the country healthcare system, with a limited testing capability, has struggled to monitor and report current cases. At the outbreak of a virus, data on cases is sparse and commonly severe cases, with a higher probability of a fatal resolution, are detected at a higher rate than mild cases. In addition, in an under-sampling situation, the number of total cases is under-estimated leading to a biased case fatality rate estimation, most likely inflating the virus mortality. Real time estimation of case fatality ratio can also be biased downwards by overlooking the delay between symptoms onset to death. In this communication, using reported data from Instituto Nacional de Salud up to December 28, we estimate the case fatality rate for Covid-19 in Colombia and some of its regions and cities adjusting for delay from onset to death. We then apply the method proposed by Russell et al., and use our corrected case fatality rate to estimate the percentage of Covid-19 cases reported in Colombia as 42.95% (95% confidence interval: 42.50-43.41), which corresponds to a total of 3'661,621 estimated Covid-19 cases in the country.