The human immunodeficiency virus (HIV) is a type of virus called a retrovirus, which can infect humans when it comes in contact with tissues that line the vagina, anal area, mouth, or eyes, or through a break in the skin.
HIV infection is generally a slowly progressive disease in which the virus is present throughout the body at all stages of the disease.
Three stages of HIV infection have been described.
The initial stage of infection (primary infection), which occurs within weeks of acquiring the virus, often is characterized by a flu– or mono-like illness that generally resolves within weeks.
The stage of chronic asymptomatic infection (meaning a long duration of infection without symptoms) lasts an average of eight to 10 years without treatment.
The stage of symptomatic infection, in which the body’s immune (or defense) system has been suppressed and complications have developed, is called the acquired immunodeficiency syndrome (AIDS). The symptoms are caused by the complications of AIDS, which include one or more unusual infections or cancers, severe loss of weight, and intellectual deterioration (called dementia).
When HIV grows (that is, by reproducing itself), it acquires the ability to change (mutate) its own structure. These mutations enable the virus to become resistant to previously effective drug therapy.
The goals of drug therapy are to prevent damage to the immune system by the HIV virus and to halt or delay the progress of the infection to symptomatic disease.
Therapy for HIV includes combinations of drugs that decrease the growth of the virus to such an extent that the treatment prevents or markedly delays the development of viral resistance to the drugs.
The best combination of drugs for HIV are those that effectively suppress viral replication in the blood and also are well tolerated and simple to take so that people can take the medications consistently without missing doses.