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The natural history of HIV infection explains why it continues to be frequently transmitted. Understanding the natural history of HIV facilitates development of optimal strategies in disease prevention, diagnosis, and treatment.
HIV enters the body through intimate blood-to-blood contact-through sexual contact, pregnancy, needle exchange, etc. The virus then infects white blood cells that express the CD4 surface marker. Following initial exposure, there is a period (4-11 days) of rapid viral replication that may or may not be associated with symptoms. This acute phase of HIV infection is often associated with nonspecific symptoms such as fever, sore throat, and rash. These symptoms typically resolve without treatment, so few patients seek medical attention at this stage. During this early stage, diagnosis is based on positive plasma HIV levels, as antibody levels are unreliable. The formation of resistant strains during acute infection has prompted the recommendation to initiate aggressive early therapy to attenuate emergence of resistant strains.
After initial exposure and rapid replication, HIV infection may progress to an asymptomatic latent phase, which can last for several years. During this time, there is a gradual diminution of CD4 cells. The prolonged duration of the asymptomatic state contributes to the difficulty of early diagnosis and the challenge in stopping spread of the disease.
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