There are 2 types of HIV that result in AIDS in humans:
- HIV-1: common
- HIV-2: Africa
Mode of transmission
- Sexual transmission: both homosexual and heterosexual. It is particularly more common among homosexual men during receptive anal intercourse. Vaginal transmission to both partners is a common mode of transmission. Oral sex is a much less effective mode of transmission although there have been documented cases.
- Transmission through HIV contaminated blood products.
- Occupational transmission: Health care worker and lab worker maybe infected. Infections resulting from self puncture resulting from a needle or a sharp object is rather low being estimated at a rate of approximately 0.3%
- Vertical transmission from the mother to the fetus (through placental blood) or infant (through breast milk).
- There is no convincing evidence of transmission through other body fluids (e.g. saliva).
Mechanism of disease
The hallmark of HIV disease is a profound immunodeficiency resulting primarily from a progressive deficiency of a the subset of T lymphocytes referred to as helper T cells, or inducer T cells. This subset of T cells is identified by the presence of a the CD4 molecule on its surface which also serves as the primary cellular receptor for HIV.
- Initial acute retroviral syndrome: affects 50% of those infected and starts 3 to 6 weeks after primary infection. Retroviral syndrome presents with fever, lymphadenopathy, sore throat, rash, myalgia/arthralgia, diarrhea, weight loss, and headache.
- Asymptomatic stage
- Generalized lymph node enlargement
- Symptomatic infection:
- constitutional disease (fever, loss of 10% body weight, diarrhea).
- secondary infection
- secondary neoplasm
Diagnosis and screening
Using the CDC system for diagnosis of AIDS, any HIIV-infected individual with a CD4+ T cell count of <200/uL has AIDS by definition, regardless of the presence of symptoms or opportunistic diseases .
The currently used screening methods include various ELISA techniques that may require confirmation with Western Blot or other tests such as DNA PCR, RNA PCR, the (b)DNA assay, or p24 antigen capture that usually take days.
There is currently no cure for AIDS or vaccine for HIV. Treatment consists of the prevention and treatment of opportunistic infections as well as the use of highly active antiretroviral therapy (HAART) which slows progression of the disease. Over the previous decades the success of these anti-retroviral treatments in prolonging, and improving, the quality of life for people with AIDS has improved dramatically.
Current HAART combinations or "cocktails" consist of at least three medications belonging to at least two classes of anti-retroviral agents such as nucleoside analogue reverse transcriptase inhibitors (NRTIs), and protease inhibitors. Patients on such treatments have been known to repeatedly test "undetectable" (that is, negative) for HIV, but discontinuing therapy has thus far caused all such patients' viral loads to promptly increase. There is also concern with such regimens that drug resistance will eventually develop. In recent years the term HAART (highly-active anti-retroviral therapy) has been commonly used to describe this form of treatment. The majority of the world's infected individuals, unfortunately, do not have access to medications and treatments for HIV and AIDS.
There is ongoing research into developing a vaccine for HIV and in developing new anti-retroviral drugs. Human trials are currently underway. Research to improve current treatments includes simplifying current drug regimens to improve adherence and in decreasing side effects.
1. Centers for Disease Control and Prevention. Laboratory testing for the diagnosis of HIV infection: updated recommendations. 2014 Jun 27; Provides updated recommendations for HIV testing by laboratories in the United States, including an algorithm for AHI detection.