Computer virus attacking my wordpress sites

Hi all, I need some expertise assistance. I have some type of virus that is working its way into my wordpress sites and altering the code. This has happend accross multiple IP address, user names, passwords and domains, different hosting companies (godaddy, hostgator, tierra.net)

I have run norton anti virus, spyhunter, malware anti malware and its not helping. the virus corrupts the code, examples here:

https://www.jarvispainting.com
https://www.thehomeconnection.com

and has now infected over 50 sites I have, any suggestions are greatly appreciated. If I upgrade to the most recent versions in most cases it fixes the initial problem, but I REALLY want to kill this virus from my computer ASAP

THANKS!!