The human immunodeficiency virus (HIV) is a sexually transmitted infection (STI; 75-85% of worldwide transmissions) that may also be transmitted through blood (3-5%), IV drug use (5-10%) or vertically (pregnancy, delivery and breastfeeding; 25-35% in developing countries). It was first identified when two very uncommon diseases (pneumocystis pneumonia and Kaposi's sarcoma) were found in gay men in San Francisco and New York in the early 1980s. A similar illness was also identified in blood product recipients and intravenous drug users. In 1983, acquired immunodeficiency syndrome (AIDS) was identified in Africa, proved in 1998 to be its place of origin. In 1984, HIV was discovered.
HIV is a retrovirus that has a special affinity for CD4 lymphocytes (T-helper cells). Usually, the normal count of these cells is 500-1500. With HIV, naive cells are affected more than memory cells, though both decline. The reduction in CD4 cells results in susceptibility to organisms controlled by T cell immunity.
The natural progression of the HIV is related to two main factors – viral load and the rate of fall of the CD4 count, neither of which are the same in every individual. 1% of all infected HIV cases progress to AIDS by 1 year, and 50% by 8 years, though there are some long term non-progressors with no AIDS even after twenty years.
The diagnosis for HIV is based on the CD4 count and indicator diseases, as well as patient symptoms. A total of 15 infections, 3 cancers, HIV dementia and HIV wasting make the diagnosis of AIDS. The most common presentations are pneumocystis pneumonia (38%) and HIV wasting (18%).
Risk factors do not include age, sex, race do not matter, but do include unprotected intercourse, multiple partners, the sharing of needles, sex for drugs, exposure to blood prior to 1985 (current risk 1:1 000 000 units), a positive tuberculosis culture, or an infected mother.
Indicators pointing toward HIV include persistent illness with weight loss, fatigue, thrombocytopenia, specific oral and cutaneous lesions, oral candidiasis, oral hairy leukoplakia, Molluscum contagiosum, Kaposi's sarcoma, AIDS-defining systemic illnesses, and pneumocystis pneumonia.
Serology (blood work) is one effective way of testing for HIV. Before this antibody test can be performed, consent must be obtained. If the test is positive, it indicates an ongoing infection with HIV, though it may take up to 6 months to become positive after exposure. Therefore, a negative result does not rule out exposure less than 6 months prior. A positive result means further work-up and a public health call for contact tracing.
If the patient is HIV positive, a CD4 count and viral load are taken to stage the disease. A complete blood count (CBC), liver profile, BUN, creatinine, electrolytes, cholesterol, triglycerides, and blood glucose are taken for monitoring diseases and drug toxicities. Serologies for hepatitis B and hepatitis C viruses, toxoplasma, cytomegalovirus (CMV), VDRL, and a tuberculosis skin test are also performed.
If the CD4 count is less than 200, there is a 10% per year mortality, even on Highly Active Anti Retroviral Therapy (HAART). Three-drug regimens are preferred for initial therapy, including Efavirenz + 3TC + AZT (NNRTI and NRTI combo) and Kaletra + 3TC + AZT (PI and NRTI Combination).
If a pregnant mother is infected, her untreated risk of transmission to her child is 25%. Starting therapy with oral AZT after 12 weeks, intravenous AZT during labour and after birth for six weeks will decrease the risk to 8%. Also, Efavirenz is contraindicated in pregnant mothers, since it is teratogenic. If the viral load is greater than 1000 copies/mL, delivery is performed by Cesarian section.
Antiretroviral therapy may also be used. The goal of antiretroviral therapy is to drive the viral load to be undetectable (<50 copies/mL), which occurs in 50-60% of patients. This type of treatment may fail due to toxicity, adherence, or resistant virus, and so an eight week recheck is the best indicator of long term outcome. Usually, this type of treatment involves two NRTI's + NNRTI or PI.
Common toxicities for NRTI's include peripheral neuropathy (D4T, DDI), anemia (AZT + 3TC), acute hypersensitivity (abacavir), and lactic acidosis.
People with HIV are especially prone to opportunistic infections, which are of low virulence in the normal population. Some of the more common opportunistic infections found in HIV include Pneumocystis pneumonia (Pneumocystis carinii), cytomegalovirus (CMV), and Candida abicans. Kaposi's Sarcoma is also a major and AIDS-defining illness not found in the normal population.