Some strains of resistant virus have been found to be less infectious. One study has suggested that resistant virus has only a 25% capacity to infect others compared to wild-type virus ^[1]. However, a consensus appears to have emerged, based on a significant body of research, that resistance mutations acquired at the time of infection may persist for many years in the absence of treatment.

This is different than what occurs in patients who develop drug resistance mutations during treatment. If these patients stop taking antiretroviral therapy, the bulk of the viral population reverts to the fittest strain of HIV in their body, the wild-type strain (although resistant virus is likely to persist in 'archived' DNA). However, in patients initially infected with a resistant strain, there is no wild-type strain archived in the body to become dominant, and random reversion of the virus to wild-type is very rare.

A British study of 14 people infected with a drug-resistant strain found that the vast majority of drug-resistant viruses persisted over two to 36 months ^[2]. Multidrug resistance in two of these cases was found to be stable for over 18 months.

Resistant virus, including acquired multidrug resistance, has been found to persist nearly unchanged after periods up to seven years in one small, six-patient study ^{[3][4][5][6][7][8]}.

A large American study found resistance mutations in 12% of a treatment-naive cohort after eight years of infection ^[9].

The M184V mutation has been seen to reverted to wild type, with a viral load increase sometimes associated with that reversion ^{[10][11][12][13]}.