Ubuntu basically provides an open-source alternative to Windows. Its level of functionality is comparable to that of Windows, and it installs like a charm.
Fedora focuses more on the latest in free and open source software like that of the business Red Hat Linux.
It is rather challenging for a virus to infect a Linux machine, though. However, it does happen. USB drives are great for passing viruses from one machine to another.
Personally, I have used Ubuntu and Mint for about 3 years and never had a virus or any malicious software. There are several AntiVirus programs available for Linux distros. You would have no problem selecting one.
Ubuntu and Mint (my favorite) provide a very pleasant OS alternative, however, they have its similarities to Windows, and the transition to them IMO is very smooth.
You will enjoy whatever distro you select.
Retired - Doin' Dis, Dat, and slapping malware.