Prevalence of infection. Prevalence of people infected with the drug sensitive virus (solid lines), the drug resistant one (dashed lines) and the sum of both (dotted lines). All cases who seek medical help receive antiviral treatment; additionally, a fraction of (a) 0%, (b) 10% and (c) 20% of all adults between 20 and 60 years of age are given prophylaxis. The grey curves and the right hand scales indicate the fractions of resistant infections among all infections. Assumptions: (1) A single drug-sensitive infection is introduced on day 0 into a Swiss population of 100,000 individuals. (2) Resistance develops de novo in 4.1% of children and 0.32% of adults who receive medication. (3) Social distancing reduces the number of contacts by 10% for all individuals; isolation additionally prevents 10%, 20% and 30% of contacts of moderately sick cases, severely sick cases at home, and hospitalized cases, respectively. (4) Antiviral treatment reduces the contagiousness of patients by 80%, their duration of sickness by 25% and their need of hospitalization by 50% if they are infected with the drug sensitive virus. (5) Prophylaxis furthermore reduces susceptibility by 50%. Upon infection, it doubles the fraction of individuals who stay asymptomatic from one third to two thirds, but only one of the two thirds becomes immune. (6) R
0 = 2.5 for the drug sensitive and the drug resistant virus (fitness = 100%).