Reinstalling might help, but it depends.
Scenario. You receive an email from "Joe". BUT, Joe's computer didn't actually send it. "Fred" who is also on both of your email lists, well it's his friend's "Steve" computer that's infected and so it's Steve's computer that sent the email to you, "spoofing" the sender's name.
So, you can see the difficulty in running down who exactly has the virus.
ANYONE who is a recipient of an email where several people are sent the same email, can then be victim of this sort of problem.
I've STOPPED sending useless stuff like jokes to multiple recipients, and although that's part of the fun of being online, it can cause problems sometimes. Also when sending to multiple recipients, ALWAYS use the Blind Carbon Copy option when possible. It could help at least a bit.