Acquired Immune Deficiency Syndrome (AIDS) is the leading cause of death in persons aged 25-44. It is characterized by a progressive decline in immune function over a period of 8-15 years, which is paralleled by an increase in susceptibility to a wide range of opportunistic infections. Cryptococcis, crytosporidiosis, and pneumocystis carinii pneumonia are a few such infections, which often end the lives of those living with AIDS. Human Immunodeficiency Virus (HIV) is the etiologic agent which causes AIDS. HIV is a member of the retrovirus family of which there are two sub-families; HIV-1 and HIV-2. HIV-1 is more prevalent and more pathogenic than HIV-2. HIV-1 is responsible for infections globally, whereas HIV-2 is found predominantly in countries of West Africa. This website will focus on HIV-1, as it is the virus responsible for the AIDS pandemic.

Obtained from IAVI newsletter. For further information visit www.iavi.org

There are approximately 16,000 new HIV-1 infections per day, 90% of which occur in developing countries. Infection is diagnosed with a simple clinical test designed to detect serum antibodies directed against the virus. Progression to AIDS is diagnosed when a patient exhibits characteristic opportunistic infections combined with a CD4 T-cell count of 200 or less. The virus is transmitted by contact with contaminated blood or bodily fluids. The World Health Organization (WHO) estimates that 80% of HIV transmission occurs via unprotected anal or vaginal intercourse. HIV can be transmitted during intravenous drug use by sharing or re-using hypodermic needles with an infected individual. Many people have become infected by receiving infected blood or blood products during transfusions. Stringent blood screening protocols are now in effect, which have dramatically reduced the numbers of individuals infected by this route. HIV can also be transmitted from mother to child during parturition, and possibly during breastfeeding. Numbers of children infected by this route have steadily decreased in industrialized countries due to the administration of anti-retroviral drug therapy to the mother before and during birth and to the infant following birth.

Obtained from www.iavi.org

HIV-1 is one of the most rapidly mutating viruses known. Because strain classification is based upon the variable viral structure, many different strains of HIV-1 have been documented. Among large populations in particular geographic locations, predominant virus strains arise which are referred to as subtypes or clades. Approximately 30% of the amino acids in the gp120 protein differ between clades. There are a minimum of 9 distinct clades (A-I), which are currently involved in the AIDS pandemic. Clade B is prevalent in the Americas, Europe, and Australia. Clades A and D are commonly found in sub-Saharan Africa, clade C in India, and clade E in Southeast Asia.

Back to HIV