Anyone know what is causing the humps in the graphs of “confirmed cases” ? Looked at this before, at first I thought it was weekends being under reported, then

Anyone know what is causing the humps in the graphs of “confirmed cases” ? Looked at this before, at first I thought it was weekends being under reported, then people going out on weekends, etc. — but now starting to think it might be the R0 (reproduction number) is very high and the virus burns itself out among a social network. Any ideas what is the source of those humps?