Question: what is the most beneficial disease to have ever infected humans ?

Zoe Vance answered on 29 Apr 2024:

Probably one of the viruses that we ended up keeping within our DNA! Some viruses integrate their genetic material into that of their host, so some percentage of our genome is made up from viruses that infected our far off ancestors – endogenous retroviruses or ERVs. The most beneficial one is probably the one that is now a syncytin gene, a gene that mammals need to have in order to make a placenta during pregnancy! Viruses have an ability to fuse with cell membranes, which is useful for them trying to get into the cell, but mammals have co-opted that to fuse lots of cells together into the placenta.