Importance of untested infectious individuals for the suppression of COVID-19 epidemics

Francisco Perez-Reche; Norval Strachan

Bearing in mind that 50% of infected individuals might be asymptomatic 7,9 , we conclude that most of those that were infected but not tested in Germany were asymptomatic. In contrast, untested individuals in other countries might include a significant number of individuals with mild symptoms in addition to those that are asymptomatic. Table 2 ). Logarithmic scale is used in the vertical axis of each plot. Table 1 . Estimates of the model parameters given in terms of the 5% percentile, median and 95% percentile. is the transmission rate, is the proportion of tested infectious (in percentage), is the proportion of tested infectious that die (in percentage), is the rate of recovery of tested infectious individuals, is the rate of recovery of untested infectious individuals, (0) is the initial number of exposed individuals and â„› 0 is the reproduction number. The proportion of tested infected individuals that die, , is smaller for the outbreak in Germany than for the other outbreaks. This might be a combined effect of the fact that infected individuals in this country were relatively young at the beginning of the outbreak 28 and the high testing rate. On the one hand, the COVID-19 fatality rate is lower for the younger than for the elderly 29 . On the other hand, the higher the testing rate, the more individuals with mild symptoms will be included in the tested infected compartment of our model. The lower death rate of individuals with mild symptoms will lead to an effectively lower death rate for the whole set of infected individuals in this compartment. We note that the specific value of for a country does not fully determine the expected fraction of deaths in the country. Indeed, we found that the predicted fraction of deaths by the end of unmitigated epidemics is not too different for different countries (medians are as follows: 0.4% for Germany, 0.9% for Hubei, 0.5% for Italy, 0.8% for Spain and 0.3% for UK).