This is a very sophisticated article from the journal Nature, regarding observations in viral shedding and replication, screening for (diagnosing) active versus convalescent disease, and some key differences in Covid-19 virulence and pathogenicity patterns, as compared with previous SARS viral epidemics.
One of the key features of this report is that viral shedding seems to exist both earlier and later in the course of the disease compared to previous SARS Coronavirus infections. This means that there is often viral shedding before symptoms start and for many days after symptoms abate, increasing the time-frame a patient can transmit the disease to others and increasing the chances that transmission will occur. This is apparently true even in mild infections and could potentially also explain the apparent increased virulence pattern. This means that the Covid-19 “R0 number” is greater than that of Influenze by a factor of 100-150%. The “R0 number” is the number of people that will statistically be infected by one infected individual. It is easier to understand this by looking at the actual numbers. Seasonal influenza has an R0 of 1. Measles has an R0 of 12-18. SARS-CoV2 R0 is 2.0-2.5, at least based on the data we have at this point in time. It is feasible that the R0 (and mortality rate) could be lower once we have tested more of the population.
Also, the jury is still out about the presence of coronavirus in the stool (gastrointestinal replication), and transmission through the fecal-oral route, similar to many other viruses. Stool does show virus but it is not clear if it actually replicates in the gut or is just swallowed from respiratory secretions (mucous or phlegm).
This article is loaded with well conducted data observations and with sound conclusions drawn, for those who can tolerate scientific writing.