If you want to get an excellent understanding of viruses and infections, without needing to go through university, for your own enjoyment of growing and sharing knowledge.
This is my recommendation:

1) Complete the youtube university lecture series `Virology' by Vincent Racaniello. 25 lectures, he uploads to not only teach his class but teach the public for free.

m.youtube.com/playlist?list=PL

Recommended prereq: 1000 level bio ― introduction to biology.

1/