Update on this. The CDC announced, today, that three major antibody test surveys will be done with one of them already underway, on hotspot areas. A national survey will be done this summer, probably because doing one now while things are changing rapidly will be of less value; another will be done soon on health care workers and some local hospitals will be doing their own shortly. We know there are significant numbers of people who test positive without symptoms, but we have no idea how many there are and how many of these are infectious carriers. On the Diamond Princess cruise ship, about 19% of passengers tested positive (they tested everyone on board) and of those almost half had no symptoms.
So far, no country has tested more than about 1% of their population and no country has more than about 0.2% of their population with positive results, which is way less than on the DP. The big question is whether we already have 1, 5, 10, 20% of people in the US or in hotspots that were actually infected and don't know it (and likely have antibodies/immunity). There are some experts out there speculating that 5-10% of the population have already been infected (will post on this later, when I have some time). This is really important testing...
The Centers for Disease Control and Prevention has begun preliminary studies to try to determine how many Americans have already been infected with SARS-CoV-2, the virus that causes Covid-19, an agency official revealed Saturday. On Friday, the agency said nearly 240,000 people in the country have been infected with the virus and nearly 5,500 have died.
Joe Bresee, deputy incident manager for the CDC’s pandemic response, said the agency hopes to flesh out the portion of cases that have evaded detection using three related studies.
The first, which has already begun, will be looking at blood samples from people never diagnosed as a case in some of the nation’s Covid-19 hot spots, to see how widely the virus circulated. Later, a national survey, using samples from different parts of the country, will be conducted. A third will look at special populations — health care workers are a top priority — to see how widely the virus has spread within them. Bresee said the CDC hopes to start the national survey in the summer; he gave no timeline for the health workers study.
“We’re just starting to do testing and we’ll report out on these very quickly,” Bresee said at a media briefing. “We think the serum studies will be very important to understand what the true amount of infection is out in the community.”
These studies — called sero-surveys — involve drawing blood from people never diagnosed as a case to look for antibodies to the virus. They are conducted by taking a representative sample of people in a city, for instance, ensuring people from different age groups are included.
https://www.politico.com/news/2020/04/04/cdc-coronavirus-blood-tests-165116
