[oblomov]

There is a theory that influenza and measles virii cause people to want to be around other people in the early, most contagious stage of these diseases.

[dennisw]

There is a theory that influenza and measles virii cause people to want to be around other people in the early, most contagious stage of these diseases.

I am not surprised. These  virii has a better chance of replicating if there is something in it that induces this togetherness feeling.  The virii got this way via evolving.