This study attempts to reconstruct the course of the epidemic in its original center, Wuhan, China. (Nature Article) The researchers are from China and examined the period from January 1 through March 8. They used a revised model, which now has the benefit of hindsight and estimate that 87% of infections were missed, so that there actually were 250,000 cases, instead of the reported number. But depending on trends in various periods of the epidemic, the number could be 260,000, 818,000 or 6.3 million. In any event, they concluded that there were a large number of asymptomatic or mild cases that simply were never tested or treated. They noted that even though the entire city underwent door-to-door checking for symptoms, these cases were missed. The authors initial transmissibility, or R number, was 3.54, but I have come to view that number as useless. Transmissibility depends on how infectious someone is, how many contacts they have and how intense the interaction is, so that an adequate dose of virus can be delivered to infect a contact, and that dose likely is highly variable. And it appears that clustering is very common. So R doesn’t tell you squat that is useful. What is apparent from the authors’ work, which presumably has China’s blessing, is that there was a much extensive epidemic in Wuhan than the world was initially told.
An interesting paper on the seasonality of influenza. (Seas. Article) While it isn’t coronavirus, the seasonality of respiratory viruses tends to be similar. The study was carried out in Vietnam, which has a variety of topographies and climates. The researchers focused on differences in absolute humidity. They found that in a tropical region, high absolute humidity may facilitate transmission, whereas in more temperate areas, low absolute humidity seemed more favorable to spread of the virus. They also found that where absolute humidity had a seasonal pattern, so did influenza-like illness. Where absolute humidity was relatively the same year-round, there was weaker seasonality to influenza.
More on whether or not this frigging virus is transmitted solely by droplets, or in part by aerosols. (Medrxiv Paper) These researchers, from the Netherlands, measured droplet size, number and volume from healthy subjects. They then applied current knowledge about viral loads and concluded that aerosol transmission was unlikely to occur frequently, especially from asymptomatic or mildly ill people.
I get really tired of stating what is obvious now over and over again. Say it with me “Children don’t get infected easily and are infrequently sources of transmission.” This antibody study was done among children and their teachers in Germany. (Medrxiv Paper) 1538 students and 507 teachers were tested. 11 students and one teacher were positive or .6%. Even in schools that had a CV case before closure, there were no clusters. 23 out of the 24 participants that had a household case were negative. Open the damn schools and don’t terrify our children by making them wear masks and doing other goofy things that make no difference. Let them be children.
This study from the UK looked at children admitted to the hospital with coronavirus disease. (Medrxiv Paper) There were 451 of these children, and the researchers concluded that in general, even the hospitalized children had much less severe illness than did adult patients. Three died, all of whom had “profound” comorbidities.
And one more study, comparing viral loads in symptomatic children and adults. (Medrxiv Paper) They found similar viral loads, but also noted that children much less frequently become infected and are most often asymptomatic, so they still aren’t likely significant transmission agents.