Have your host verify the virus is actually on your site and not an ad. They should also be able to remove it for you if you pay for managed service. Also take measures to ensure your local machine is not infected and being used to infect your site(s).

I think you should contact your hosting service about it... by the way how do you know your site or blog is affected by virus?

The only time I have had a problem was like was already mentioned-it was an ad script that was rotating through external ads that were not hosted on my pages. The ads were all infected, so I simply disabled the script and it was all ok.

Also make sure your apache binary is not infected. We found this clever exploit a while back on an unmanaged Linux server. You can try `grep test_header_filter /usr/local/sbin/httpd` to identify an exploited httpd if you have root access.