I can not go in details but a person in a factory got to illegal party and went to work. He is known to be a conspiracy theory believer. Many coworkers got it there, factory closes. Older children play with young kind who get no symptoms. They infect others.
We have mapped it all even before the goverment found it to be the route. The person is not in any law danger because he only caused few deaths and many more illness. Of course this is simplified and anonified.