Originally Posted by ScottGem
Yes its possible for someone to deliberately or inadvertently upload a file with a virus in it.
No, you can't assume the site operators are scanning files unless they state that they are. The only way that a virus would target FTP sites is to upload itself whenever the user connected to an FTP site or even automatically upload to any FTPs the user has gone to.
You can do a search on any virus name to get info about its properties.
As long as your A/V software is up to date, it should scan any downloaded files and warn you if it is infected.