If it actually was a virus, then that's what it looks like. It's almost impossible to know at this point, because they've been a little more... unpredictable than they used to be. They usually only last a few days, and the people affected typically remember what happened during them, but there have been a few instances of viruses lasting longer with only a handful of people affected lately.

Then there are cases where people just disappear without a trace, only to come back months later with no memory of anything at all, including their time at the community...