Antibody testing conducted in some of Boston’s poorer and hardest hit areas indicated that about 10% of the population in those neighborhoods has had a past infection. (Boston Article) Another 2.6% tested positive for the coronavirus infection. So extrapolating to Boston’s entire population, which is estimated at 710,000, around 85,000 residents have been or are infected. The mayor said he thinks, based on his discussions with the researchers who did the study, that the results are low. Boston has reported about 11,500 cases by positive infection testing, so in reality there are about 7.5 undetected cases for every reported one. All of these undetected cases can be assumed to be asymptomatic or mild. Boston also reported the followup on its attempts to test every homeless person. 2200 have been tested and 32% were positive for current infection, again largely asymptomatic.
And in the “why I hate the media” department, one Boston newspaper headlined this development as “90% of Boston residents not exposed to the virus yet” or something like that. First of all, as we have repeatedly pointed out, not everyone who is exposed is infected, so the fact that someone isn’t infected doesn’t mean they weren’t exposed. Second, let’s be sure to paint this in the most negative way. The very, very positive message for people in Boston is that a very low percent of infections in the general population have resulted in serious illness. And if the research about variation in susceptibility is right, the city may be well on its way to population immunity.