Are bugs that bite the way in which most diseases including HIV are spread?

Actually very few diseases are transmitted by insects and their relatives. But when it comes to the impact overall, they're perhaps just as good at transmitting diseases as people coughing and sneezing. If you look at the number of cases of malaria each year, and we're talking about tens of millions, we get about two million people die of malaria each year in sub-Saharan Africa. The population at risk is several hundreds of millions, so the chances of getting a disease from an insect are much higher in certain parts of the world, even though the variety is very small. To be a virus transmitted by an insect, you have to be a very special type of creature in that you have to be able to survive going into the insect's gut and pass through into its blood and travel to the salivary glands. It then has to survive transferring back into the human. HIV just can't do that, but malaria can.