It doesn't hurt to have some anti-viral medicine handy as long as...
1. It really is what you're paying for - there's a lot of charlatans out there.
2. It will work against the virus you want to protect yourself against. No real way of knowing this until and unless the bird flu virus mutates to a human to human virus but research so far suggests that Relenza will be more effective than Tamiflu.
3. You're not thinking that is the most effective preventative measure.
Kindest regards,
Andrew Cavanagh
You can get a more detailed article on the drugs and bird flu at... Bird Flu