The person who originally contracted and spread COVID to your cluster. Generally this person got the vid from an unknown source and spread the virus to his friends. The best way to identify your werewolf is through contact tracing. Named the werewolf due to the old legend that all werewolves descend from an original werewolf who infected the other werewolves.
Bob: I have COVID and I got it through Bill. Bill got it from Jimmy who got it at a Lame Impala concert. I guess Jimmy is my COVID werewolf.