Quickly, a couple of antibody survey papers. The first comes from Brazil, which has been hard hit, but appears to be on the downslope. (Medrxiv Paper) The survey was done in a secondary city and found a 1.4% prevalence, which was 15 times the detected infection level.
India is another hard hit country. This paper examined antibody prevalence in Mumbai. (Medrxiv Paper) This was also a representative sample and compared slum to non-slum areas. The slum areas had a prevalence of 54% and the non-slums were at 16%. The prevalence is far higher than the number of detected infections. The difference in the socio-economic areas is probably largely due to population density. These high prevalence rates are the one thing that makes me question population immunity at lower levels of infection, but it could be that while lower prevalence in less densely populated areas is enough to slow transmission, higher transmission continues to occur in denser areas.
Also quickly, a paper that estimated future earning losses from keeping children out of school. (SSRN Paper) The authors find large losses in lifetime earnings for each year of education lost, with the biggest impact among low-income children.
Another paper attempting to ascertain how long the virus may remain viable on solid surfaces. (Medrxiv Paper) The virus is more stable under conditions similar to spring and fall in temperate climates, that is, lower temperatures and relative humidity. But it did not have a very extended period of viability on any of the 12 surfaces tested, generally in the range of a few hours, although some virions might last for longer periods.
This study looked at the prevalence of various respiratory viruses in young children diagnosed with bronchiolitis infection. (Medrxiv Paper) The most common virus was RSV at 59%, followed by rhinovirus at 19%. Influenza and coronavirus were each found in around 3%. No child was reported as having CV-19 infection.
Another paper covered the topic of viral clearance. (Medrxiv Paper) It comes from Australia and involved tracking 958 positive patients, about 250 of whom had multiple tests on follow up. Very long clearance time, but no description of testing method in terms of cycle time. The authors did acknowledge that after a few days they were likely finding fragments. Not sure why culturing wasn’t done to determine viability. Older people took longer to clear the virus than did younger ones.
One notable feature of the epidemic around the globe has been the heavy impact on nursing home residents. This paper described the experience of nursing homes in a region of Belgium. (Medrxiv Paper) The mortality rate among nursing home residents was 130 times that in the general population. It was highly variable across nursing homes, as it has been in the US. One of the authors’ conclusions is that that nursing home population should be addressed as a separate group for managing the epidemic response.
More research on T cells, antibodies and other immune response issues. The first dealt with a correlation between T cell response and hospitalization rates. (Medrxiv Paper) The researchers found that hospitalization rates rose 4.5% for each year of life. Interestingly, they said that thymus volume and T cell production declines at a similar rate. Similar patterns are seen with other infectious diseases. Men have greater T cell declines, and higher rates of severe disease. People under the age of 20 have an apparent immune protection 53% to 77% greater than would be predicted, suggesting either cross-reactive immunity or other immune responses.
This paper compares the immune response to influenza with that for CV infection. (Medrxiv Paper) In general there is a robust T cell response to both infections, but CV infection seems more often to lead to T cell exhaustion and may be less focused on memory or helper T cells. They detected some cross-reactivity with seasonal coronaviruses.
And this study was a systematic review of antibody responses. (Medrxiv Paper) 150 papers were included. The researchers’ summary of findings included that almost all patients generate an antibody response, although in some it may be at a low level. These antibodies include neutralizing antibodies. Cross-reactivity with seasonal coronaviruses may exist but cross-neutralization is limited.