Man flu over the cuckoo's nest

Yes, I have man flu. Jen has been feeling ill for a few days solid, but she has gone to work without complaint. I on the other hand have felt grotty all day, and so have whinged about it since Jen picked me up from my training. I have sniffled my way through dinner and have moaned and groaned on the couch whilst we watched a Bug's Life (for Emma - honest!). Why is it that men get sicker than women?