Relative infectuousness of asymptomatic and symptomatic COVID-19 infectives - An analytical time table

The question on the relative infectuousness of asymptomatic and symptomatic infections of COVID-19 is surrounded by contradictory clinical findings and confusion. This article undertakes a critical review of the available clinical literature on this topic, from the perspective of individual infection cycles and from the perpective of epidemiologic dynamics. Using the available results from the clinical and virological literature, we analyse how they fit in the time table of individual infection cycles, separately for the symptomatic and asymptomatic infection mode. The time table is based on a Susceptible-Infected-Resolve (SIR) mainframe, but the Infection compartment is sub-divided in 5 clinical stages for the symptomatic infection mode and 3 clinical stages for the asymptomatic infection mode. From the perpective of epidemiologic dynamics, the only period that matters is the time interval that infectives shed viable virus material, which is capable of self-replication in another host. The duration of this period can only be assessed by subjecting the positive RT-PCR tests samples to viral culture to isolate virus material that is able to self-replicate. Doing this on a daily basis reveals the time profile of effective infectuousness, separately for symptomatics and asymptomatics. For mild to moderate symptomatic cases we calculate that this period is 14 days on average, while for asymptomatic cases it is 9 days. Most of the replication-competent virus material is emitted during the first 4 days of this period, with few differences between symptomatics and asymptomatics. Because they shed virus over a longer interval, symptomatic infectives are likely to constitute the largest source of secondary infections. However, asymptomatic infectives have the largest average daily infectivity, because they shed most infective virus load during a short period. If the contact network of susceptibles has a sufficiently high share of asymptomatics in their early infection stage, the asymptomatic persons become the dominant source of secondary infections.