In at least 1 episode of Red Dwarf there where positive viruses. Have the positive viruses ever been used in the Red Dwarf books?
From the Red Dwarf Wikia synopsis of the book:
Back on the Mayflower, Kryten and Kochanski, in their study of the many viruses, come across both negative viral strains and positive ones (which, unlike viruses such as flu and rabies, are beneficial to their hosts). In particular, they find the Luck virus, which bestows the infected person with a brief dose of good fortune...
After "Quarantine", the positive viruses wouldn't be seen again until Season 8's "Back in the Red".
Of the other three novels written (Last Human is the third of four), the first two, Infinity Welcomes Careful Drivers and Better Than Life, deal with earlier episodes/situations, before "Quarantine". The fourth book, Backwards, takes scenes from episodes before and after "Quarantine", but not the episode itself, nor as late as "Back in the Red".