First, someone who has your email address got a virus. It's likely that they all originate from the same IP. I've been there. Had this happen for several months straight. It was a slightly different virus than those you've mentioned, but it was one where the originating IP was not falsified. I contacted the ISP and they told me it wasn't one of their users and that the IP was false. I asked DH and they confirmed the IP it came from was correct. I went back to the ISP a couple times and they insisted it wasn't someone on their network.
At that point I played my legal card and, since the originating ISP and their ISP were based in my state, I contacted their ISP and quoted the spam law on this. I said since the emails violate the spam law, and that the ISP under them refuses to do anything about it, I considered them to be assisting in violating the law. I had received tens of thousands of emails over several months. I also quoted the law which states I'm entitled $500 per email. I informed them that if they let the ISP under them continue to assist in these illegal actions, I would seek full damages.
The parent ISP agreed that the IP was part of their network and said they would take care of it. A few days later the emails stopped and they never started up again.
If you don't want/know how to figure the above out, then you can setup a rule in Mail.app to send those emails to the trash based on the sender's address (I'm guessing it stays the same.) You should be able to find some sort of consistency.
Don't worry, if you're using Mail.app your client is not infected, nor will it become infected by any virus in existence to today.