Human immunodeficiency virus (HIV), a lentivirus, causes acquired immunodeficiency syndrome (AIDS) which is a condition in humans were the immune system begins to fail, leading to life-threatening opportunistic infections. Infection is transferred through bodily fluids where HIV is present as both free virus particles and within infected immune cells. The four most common routes of infection are unsafe sex, contaminated needles, breast milk, and transmission from an infected mother to her baby at birth. Blood screens have largely eliminated transmission through blood transfusions and infected blood products in the developed world.

The World Health Organization considered HIV infection to be a pandemic. From 1981, when it was discovered, to 2006 AIDS killed more than 25 million people and it infects about .6% of the world’s population. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but routine access to antiretroviral medication is not available in all countries.

HIV infects primarily vital cells in the human immune system such as helper T cells, macrophages, and dendritic cells. HIV causes low levels of CD4+T cells through direct viral killing of infected cells; increased rates of apoptosis in infected cells; and by killing infected CD4+T cells by CD8 cytotoxic lymphocytes that recognize infected cells. All of this causes the body to be more susceptible to illness.

People infected with HIV-1 who don’t receive treatment often develop AIDS. These people often die from other infections due to the failure of the immune system. Most HIV infections progress to AIDS within 10 years. Without antiretroviral therapy most AIDS sufferers will die within a year.

HIV-1 and HIV-2 are the two types of HIV known to exist. HIV-1 was the first to be discovered and is more virulent, more infective, and the major cause of HIV infections globally. HIV-2 is largely confined to West Africa due to its low infection rate. The infection occurs in four basic stages: incubation period, acute infection, latency stage and AIDS. Incubation is asymptomatic and lasts between two and four weeks. Acute infection last on average about 28 days and can include fever, lymphadenopathy, pharyngitis, rash, malaise, and mouth and esophageal sores. Latency stage shows few to no symptoms and can last from two weeks to twenty years. AIDS usually shows through various opportunistic infections.

Most individuals develop an influenza or mononucleosis-like illness called acute HIV infection. Symptoms are non-specific and thus are often not recognized as signs of HIV infection. Immune defense reduces the number of viral particles in the blood stream which is the start of secondary or chronic HIV infection.

Once CD4+T cell-mediated immunity fails then tumors and infections start becoming common. Pneumonia is a common and fatal disease in AIDS victims. Most HIV infections are acquired through unprotected sex. Many people infected with HIV are unaware they are infected with the virus. Most of this is due to lack of screening although modern tests are extremely accurate. There is no cure or vaccine for HIV or AIDS.

However, when therapy is deferred death rates are almost twice as high. HAART is a new treatment that neither cures the patient nor uniformly removes all symptoms. It would also take more than a lifetime to clear HIV from the body using HAART. Despite all of this individuals who use HAART show remarkable improvements in their general health and quality of life. The majority of those infected don’t have access to or can’t afford anti-retroviral drugs. A chemical called BanLec was reported to inhibit HIV replication.

HIV is through to have developed in non-human primates in sub-Saharan Africa and was transferred to humans in the 19th or early in the 20th century.