PDAnet doesn't provide any protection against viruses, as far as I know. Just like your DSL/Cable modem doesn't provide any virus protection. That's why you have antivirus on your computer.
Looking online briefly, there are a couple of cases where people THOUGHT they got a virus from pdanet. However, it's either because there were downloading from sketchy sites (4share, etc) or because their AV program was being hypersensitive. As long as you're downloading it from a reliable place, it's fine. Thousands of people use it.
(ok, on second thought I might have misread your second question. You might have meant "Has PDAnet ever found viruses?" In which case, pdanet is not an AV. It won't find viruses, it just just pipes the phone's data connection to your computer).
Are you just asking out of curiosity/paranoia or do you think pdanet gave you a virus? The more specific you are, the better we can help...