Antiretroviral drugs prevent the reproduction of a type of virus called a retrovirus. The human immunodefiency virus (HIV), that causes acquired immune deficiency syndrome (AIDS), is a retrovirus. These drugs are therefore used to treat HIV infections. These medicines cannot prevent or cure HIV infection, but they help to keep the virus in check.

Viruses are tiny, disease-causing particles that are unable to reproduce on their own. They must invade the cells of other living things and take over the cells' machinery in order to multiply. In the process, they cause illness. HIV is a specific type of virus called a retrovirus. It slowly weakens the immune system by invading and destroying special immune cells that help defend the body against infections.

Antiretroviral drugs do not kill viruses, because that could also damage or kill the cells the viruses have infected. Instead, these drugs block the...