IT/Virus??/Email help

[AAlmeter]

Strange situation we have here...

My uncle (bored and retired) sends out frequent emails of jokes, politics, etc. I never really paid any attention to the recipients until last week. He sent out an anti-Obama email. Then someone with a rather unusual first name hit "reply-all" so I was copied on it. I also noticed that this person mentioned his affiliations with the Democratic party. Kind of odd, as I know one of my brother's friends had this first name and had worked for the local Dem party.

Today, a similar situation happened, but I bothered to look at the entire list of who my uncle is forwarding these emails to. There are a lot of my brother's personal and professional contacts on that list, and my uncle knows none of them (he lives in NM, we're in NY).

I quickly forwarded the email to my brother, who is not copied on the emails to alert him to this fact.

It appears as though somehow my uncle has my brother's email address book and is unknowingly bulk emailing some emails to these people. Another email I received today from my uncle on the subject of tort reform was only sent to select people (uncle's family and friends), so these emails are not automatically being copied to everyone. Also, my brother is always especially careful with his email, and I have no record of any sort of contact between him and my uncle via email.

Any thoughts on this one? Ghosts maybe?