virus will be transmitted to another individual. hiv has evolved to maximize the number of infections to other hosts, and this tendency for selection to favor intermediate strains shows that hiv undergoes stabilizing selection. the virus has also evolved to become more infectious between hosts. there are three different mechanisms that allow hiv to evolve at a population level. one includes the continuous battle to evolve and overcome the immune system which slows down the evolution of hiv and shifts the virus’ focus towards a population level. another includes the slow evolution of viral load due to viral load mutations being neutral within the host. the last mechanism focuses on the virus' preference to transmit founding viral strains stored during the early stages of infection. this preference of the virus to transmit its stored genome copies explains why hiv evolves more quickly within the host than between hosts. hiv is evolving to a milder form but is "an awfully long way" from no longer being deadly and new severe variants are still appearing. drug resistance mutations isolates of hiv-1 and hiv-2 with resistance to antiretroviral drugs arise through natural selection and genetic mutations, which have been tracked and analyzed. the stanford hiv drug resistance database and the international aids society publish lists of the most important of these; first year listing 80 common mutations, and the latest year 93 common mutations, and made available through the stanford hiv rt and protease sequence database.