How does resistance affect treatment?

In a person not on antiretroviral (ARV) treatment, the population of viruses will tend to be those most 'fit' to reproduce. Resistant viruses will occur at random and form only a minority part of this population.

While taking ARVs, drug-sensitive HIV will be suppressed, that is, prevented from reproducing. If few or no drug-resistant viruses are present and drug levels stay high enough, HIV should remain suppressed. However, there is usually a small population of virus that keeps reproducing. Over time, this 'selective pressure' can shift the pool of HIV in the body to include fewer drug-sensitive viral strains and more drug-resistant strains.

Over time, variants accumulate additional mutations. Some are harmful to the virus and cause it to stop reproducing. Other variants go on to accumulate additional mutations and given time, ARVs can lose their ability to bind to this virus and prevent replication. This is how undetectable viral load once again becomes detectable.

Drug resistance is the most common reason for ARV treatment failure. Viral load, which drops and remains suppressed during successful HIV treatment, is likely to rebound if a resistant virus population emerges.

Drug-resistant virus may be present from the time of infection (see Transmission of resistant HIV), develop before treatment begins, or develop after starting treatment – particularly if ARV drug levels are not consistently high enough to suppress viral replication.

Community Consensus Statement on Access to HIV Treatment and its Use for Prevention

Together, we can make it happen

We can end HIV soon if people have equal access to HIV drugs as treatment and as PrEP, and have free choice over whether to take them.

Launched today, the Community Consensus Statement is a basic set of principles aimed at making sure that happens.

The Community Consensus Statement is a joint initiative of AVAC, EATG, MSMGF, GNP+, HIV i-Base, the International HIV/AIDS Alliance, ITPC and NAM/aidsmap

This content was checked for accuracy at the time it was written. It may have been superseded by more recent developments. NAM recommends checking whether this is the most current information when making decisions that may affect your health.

NAM’s information is intended to support, rather than replace, consultation with a healthcare professional. Talk to your doctor or another member of your healthcare team for advice tailored to your situation.