This reminds me of William S Burrough’s “Cities of the Red Night,” in which a deadly plague appears suddenly. The character Dr. Pierson is a heroin addict, and helps discover that heroin is prophylactic against the fever:
“A top government official bluntly warned: ‘Virus B-23 now loose in our overcrowded cities, is an agent that produces biologic changes in those affected – fatal in many cases, permanent and hereditary in those who survive and become carriers for that strain, which as a matter of survival they will spread as far and fast as possible to destroy enemies and quite literally make friends.’ Junkies, however, are only lightly affected by the virus and remain characteristically unchanged.
…
“He recovers in the fear because of his addiction, and the word went out that the junk was the only insurance against the fever. No stemming the black market the Government concedes and legalises. Now begins a deadly war to extermination between the junkies and the fever-freaks.”
I first heard it in this collection, which I bought 20+ years ago — https://www.discogs.com/sell/release/721207. I can’t recommend it enough; Burroughs is fantastic at reading his own work, even blind drunk as he clearly was in some of these recordings.
“A top government official bluntly warned: ‘Virus B-23 now loose in our overcrowded cities, is an agent that produces biologic changes in those affected – fatal in many cases, permanent and hereditary in those who survive and become carriers for that strain, which as a matter of survival they will spread as far and fast as possible to destroy enemies and quite literally make friends.’ Junkies, however, are only lightly affected by the virus and remain characteristically unchanged.
…
“He recovers in the fear because of his addiction, and the word went out that the junk was the only insurance against the fever. No stemming the black market the Government concedes and legalises. Now begins a deadly war to extermination between the junkies and the fever-freaks.”
https://en.wikipedia.org/wiki/Cities_of_the_Red_Night