There are a bunch of serological surveys going on right now in the US: https://www.sciencemag.org/news/2020/04/unprecedented-nationwide-blood-studies-seek-track

There are a bunch of serological surveys going on right now in the US: https://www.sciencemag.org/news/2020/04/unprecedented-nationwide-blood-studies-seek-track-us-coronavirus-spread https://www.sciencemag.org/news/2020/04/unprecedented-nation...