They have an announcement on their web site[1] and on twitter[2].
Also the web client shows information about the executing tasks (e.g. [3][4]). The COVID19 tasks are prioritized and will be executed when you keep the target settings of the client at default ("Any").
[1] https://foldingathome.org/2020/03/10/covid19-update
[2] https://twitter.com/foldingathome/status/1238568504200253442