HIV/AIDS: Transmission, Epidemiology, and Community Health

Introduction to HIV and AIDS

Human immunodeficiency virus (HIV) is a virus that can lead to the development of acquired immunodeficiency syndrome, or AIDS, in susceptible individuals. Although the human body can eliminate some types of viruses, it cannot eliminate HIV — so once a person contracts HIV, they carry the virus for life.

Symptoms, Transmission, and Disease Progression

Within the body, HIV spreads via bodily fluids and targets specific cells of the immune system known as T cells, or CD4 cells. As HIV moves through the body, it destroys such a large number of T cells that the body can no longer effectively fight off infections and other diseases. This is the point at which an HIV infection progresses to full-blown AIDS.

Although HIV presents with many symptoms, testing is necessary to confirm a diagnosis. Many people who become infected with HIV remain symptom-free for years — in numerous cases, for ten years or more. Despite the potential severity of the disease, many people report experiencing only flu-like symptoms two to four weeks after exposure, sometimes describing them as "the worst flu ever." For others, a more conventional symptom pattern emerges: fever, enlarged lymph nodes, sore throat, and rash. Because these symptoms are not unique to HIV and overlap with other viral and bacterial infections, anyone who presents with them and may be at risk for HIV should be tested promptly. Symptoms may last anywhere from a few days to several weeks. Importantly, an HIV test may not detect the virus during this early window period; however, infected individuals are highly contagious at this stage.

HIV is transmitted during any of three disease stages: acute infection, clinical latency, and AIDS. The acute infection stage occurs within two to four weeks of initial infection. The infected person may feel ill with flu-like symptoms — a response technically referred to as acute retroviral syndrome (ARS) or primary HIV infection. Not everyone develops ARS, even though it represents the body's natural response to the viral invasion. During this stage, large quantities of HIV are produced as the virus uses CD4 immune cells to replicate, destroying those cells in the process and causing a sharp drop in the CD4 count. Viral levels in the blood are at their highest during this period, making transmission to others especially likely. A healthy immune response will eventually lower the viral load and allow the CD4 count to rise, though it may not return to pre-infection levels.

The stage known as clinical latency is a period of relative dormancy. HIV remains active in the body but reproduces at a much lower level; this phase is also called asymptomatic HIV infection or chronic HIV infection. Many HIV-positive individuals experience no symptoms during this period. People undergoing antiretroviral therapy (ART) may remain in clinical latency for several decades, while those not on ART may progress through this phase in roughly a decade or less. ART does not eliminate the possibility of transmission, though it greatly reduces the risk. Toward the middle or end of clinical latency, viral load typically begins to rise again and the CD4 count drops, often accompanied by the return of symptoms as the immune system weakens.

The advanced stage of infection is AIDS, at which point the immune system is so severely damaged that the individual becomes vulnerable to opportunistic illnesses — infections and cancers that would not normally pose a serious threat to a healthy immune system. AIDS is diagnosed when the CD4 count drops below 200 cells per cubic millimeter of blood (200 cells/mm³), compared to a normal range of 500 to 1,600 cells/mm³. The presence of one or more opportunistic illnesses also constitutes grounds for an AIDS diagnosis, regardless of CD4 count. Without treatment, individuals diagnosed with AIDS typically survive approximately three years; the presence of an opportunistic illness shortens this to roughly one year. Medical treatment is essential to prevent death at this stage.

Treatment Options and Mortality

The mortality rate associated with HIV is high, and most people cannot be cured of the disease. The rare documented cases of HIV cure have generally involved treatment for an otherwise terminal cancer, using aggressive therapies that are themselves life-threatening. For this reason, physicians resort to these treatments only when the HIV-positive patient would otherwise die from the cancer.

The standard treatment for HIV is antiretroviral therapy (ART). ART has dramatically prolonged the lives of HIV-positive individuals and also reduces the risk of transmission to others. Treatment has been shown to be most effective when HIV infection is identified and treated early — underscoring the importance of encouraging individuals who present with possible HIV symptoms to seek testing as soon as they suspect they may be ill.

Without treatment, HIV is nearly universally fatal. The virus works steadily to overwhelm the immune system, ultimately resulting in AIDS. Treatment has been shown to both slow and prevent progression from one stage to the next, and is therefore considered beneficial for infected individuals at all stages of the disease.