This study tracked the staff of five skilled nursing facilities in Colorado to ascertain the level of asymptomatic infections. (Medrxiv Paper) The workers were tested weekly for five weeks, but it wasn’t always the same workers every week. There was substantial variation across the five skilled nursing facilities in level of infections, from one facility that had no infections to one that began with a 22% infection rate. Infections occurred in all job types within the facilities. The rate of infection declined over the study period. It was unclear if any of those infected eventually became symptomatic, but they all were asymptomatic when they tested positive. The study indicates the importance of ongoing testing of staff in these facilities.
This paper looked at viral load by patient age. (Medrxiv Paper) Viral load is important because it almost certainly in correlated with severity of illness and with ability to infect others. The researchers used data from 3300 patients in Germany. People under the age of twenty, however, accounted for only a small portion of the patients. Viral loads at a level the researchers considered high enough to be infectious existed in 29% of children age 6 and under, 37% of children aged 19 and under and in 51% of people aged 20 and over. Two test types were used and gave somewhat different results, which would be concerning. Another paper on viral loading concerned 28 patients in Japan. (Medrxiv Paper) The researchers, based on this small sample, found lower viral loads in children than in adults at initial testing, but the difference disappeared at subsequent followup testing as loads declined among all patients, and lower loads in asymptomatic cases versus symptomatic ones. The authors thought the results suggested a lesser role for asymptomatic transmission.
Another antibody prevalence study, this one from Belgium, which has been hit hard by coronavirus illness. (Medrxiv Paper) During the month of April, the rate rose from about 3% to around 6%.
This study purports to summarize studies looking at the effectiveness of lockdowns by studying border counties in states with and without a lockdown. (Medrxiv Paper) The authors found very low differences, less than 3%, in infection growth rates. More evidence that lockdowns made little difference in slowing spread.
And finally, this paper found fairly high levels of asymptomatic infection and antibody presence in health care workers in a London Hospital. (Medrxiv Paper)