Another strong study on the adaptive immune response to infection. (Medrxiv Paper) It comes from France and looks at memory B cell response in severe and mild disease patients. Those cells aid in the production of antibodies. These cells were tracked for up to six months. They began to develop shortly after infection and they recruited cross-reactive betacoronavirus B cells to assist in fighting infection. Over the course of time, a robust memory B cell population developed. The response tended to be stronger in patients with severe disease.
The Mayo Clinic is reporting that 900 of its staff have recently been infected with CV-19. The clinic said most of the transmission occurred in the community. If that is true, it isn’t likely the staff’s fault, if anyone knows how to protect themselves it is health care workers. Mayo is worried about staff shortages, but earlier in the epidemic it was laying people off due to lack of patient volume. (Mayo Story)
Another news story suggesting both ease of transmission and that we might want to dig into hospitalization numbers a little more is found in the Miami Herald. (Miami Story) According to the story, of 898 patients admitted to hospitals in the area in the last week and testing positive for CV-19, 471 or more than half, were admitted for a reason other than coronavirus and had no symptoms. The author tries to make this into a scary story about community spread, but what it really shows is how for most people, they don’t even know they have CV-19.
It isn’t just Minnesota that is wasting millions on contact tracing and diverting effort from more effective mitigation approaches. A Wall Street Journal article notes the futility of these efforts around the world. (WSJ Article) No country mentioned in the article is able to trace even 25% of infections. Since we don’t have a definite answer yet to the question of exactly how survivable CV-19 is in the environment, how it can travel and what an infectious dose is; contact tracing that presumes transmission occurs in some defined encounter between individuals is a waste of time. I will keep saying it, this is a sneakily transmissible virus.
Okay, a few antibody prevalence studies, been a while since we talked about those. How about Chicago? According to this study, (Medrxiv Paper) prevalence was a huge 20% among about 1545 participants, fairly randomly selected. This is more than ten times the number of reported cases.
How about a meta-review of prevalence studies? This paper attempts to synthesize global studies. (Medrxiv Paper) On average, the studies suggested infection levels 12 times the reported number of cases. Prevalence estimates varied widely by geography.
One more, from India. (Medrxiv Paper) Seropositivity averaged 51% across five areas in the city of Pune. Astounding and far larger than the reported number of cases. These kinds of numbers do make me wonder about low population immunity threshholds, but they also demonstrate that the vast, vast majority of infections are completely asymptomatic. Spread was lower currently in areas with higher levels of antibody positivity.
How many virions or virus particles does an infected person have? Inquiring minds want to know. These researchers tried to find out. (Medrxiv Paper) According to them, about one billion at peak infection. Think of your immune system trying to cope with that and keep them from replicating and infecting new cells. No problem, according to the authors, your body produces larger numbers of antibodies and T cells.
Think vitamin D may have an effect on CV-19 disease? This study suggests not. (Medrxiv Paper) The study was conducted among 240 patients hospitalized with severe illness in Brazil. Half were given vitamin D3 supplementation. Their levels went up, but no difference was observed for mortality or other outcomes. It might still be that taking supplemental vitamin D offered a protective effect against getting infected.
I have mentioned my fear that too aggressive suppression of the virus may encourage mutations that enhance its survivability, transmissibility and infectiousness. This news story from Australia needs to be further verified and the strain tested. If true it is exactly what might be expected. Sometimes it is best to leave bad enough alone. (ZH Story)