FWIW, I do consider it POSSIBLE though extremely unlikely--esp considering that there is no known case of mosquito transmitted HIV.
1)the feeding canal and the salivary canal of the mosquito proboscis(needle) are separate.
2)the HIV virus is digested by the mosquito and henceforth does not survive.
3)the number of infectious particles(virions) that are involved are generally going to be insufficient to cause infection.
Remember that the host has numerous defenses. It is not as simple as a germ gets in you and you get sick. It takes a certain infectious dose to overcome defenses and cause infection. This of course is highly variable and depends on the nature of the organism, the host and imunnocompetence of same, infectious dose, etc. Some bacteria need a very small infectious does to cause illness, even death. Others require infection with a great number(several factors account for this). For instance, someone, even someone with some immunity to a specific bacteria may become ill if exposed to a sufficient number of bacteria. Viruses are more complicated as they invade the individual cells and take over the machinery of that cell to make new virus particles(virions) which are then typically released by the cell to invade others, etc, etc.
There are many different encephalitis viruses, FWIW. Also included in mosquito born viruses are Yellow Fever and Dengue. Malaria is a protozoal parasite and is far different from viruses and bacteria. There are others.
Other encephalitis viruses in the US are St. Louis Enceph(SLE), Eastern Equine Enceph(EEE), Calif or Western Enceph, Lacrosse Enceph, etc. EEE has a high mortality rate comparable to others though it is likely that most subclinical cases of infection with these viruses go unrecognized and are self limited. There is no cure, Treatment is symptomatic and supportive.
Usual life cycle of these is mosquito--bird--mosquito although, clearly, other species do become hosts.
Viruses do not have spores. Anthrax does and is much larger than 5 microns. Bacteria and viruses are as different from one another as we are from a fluke worm. In fact, there are many different viruses which invade and infect bacteria. Often it is proteins coded for in viral RNA or DNA that has been intercalated into
the bacterial genome which accounts for some of the most virulent toxins and hence the most deadly bacteria.
Condoms are not a guarantee but have been shown to be effective in general.
If you're interested I have an MD and a BS in microbiology. Hope I answered your questions.