According to news reports, we are finally getting some antibody testing for coronavirus infection. The FDA has approved at least one test, and I believe there may be other labs with their own tests. These tests are critically important for policy-makers and for individuals, especially those who work in settings where they are at high risk for contracting the disease. The CDC effort apparently will be limited to certain geographic locations, which I don’t understand, since even if you are conducting a formal study, you could allow more expansive testing outside the study. One set of locations will be “hot spots” like New York City. Others will be areas with less extensive spread of infections.
More research on virus shedding through respirations, which sounds mundane but is very important in understanding what measures may help stop transmission. A study in Nature Medicine (NM Study) discusses the efficacy of face masks in cutting transmission. The researchers first identified the nature of infectious agents in exhaled breath and found that both in droplets (which tend to fall) and aerosols (which tend to remain suspended in the air for some period) there were a variety of influenza viruses, coronaviruses and other infectious agents. They created a randomized study group of around 246 people. Half of this group had at least one respiratory virus in their exhalation. 90% of that group of 123 people had a respiratory virus infection, with 17 having coronavirus (not necessarily the Wuhan virus, in fact probably not, we all walk around with these viruses most of the time), and 43 with influenza. People tended to have more virus particles in their nose than throat. People did shed virus particles in droplets and aerosols but not in large numbers. One obvious conclusion is that while coronavirus can be transmitted by air, it may require close or extended contact. People wearing face masks had substantially fewer coronavirus particles that passed the mask in either droplets or aerosols, but influenza particles were reduced only in droplets. So face masks likely help.
In another transmission related story, it appears that people may be able to spread the virus for only about 1 to 3 days before symptoms start, according to a World Health Organization official. (WHO Story) This appears contradictory to some earlier reports suggesting that people could be transmitting for a much larger number of days before they became symptomatic and that even asymptomatic individuals, those who never got symptoms, could be transmitters. This report suggests that people who don’t get symptoms are not able to be transmitters. The report also says that droplets from the nose and mouth containing virus particles seems to be the most common method of transmission. The likelihood of infection also appears linked to how big a dose, or how many virus particles, an individual picks up.