In one way, “seroconvert” simply refers to the moment when enough virus appears in the blood so that it becomes detectable in a sample. In that sense, other viruses may also be said to seroconvert.
But with HIV, the story is more complicated. Here’s a link to a comment I once made to Eric Griggs, another Quoran you may know.
“You know, I’m not entirely sure why some of us use the word seroconvert.” @jfinn6511