Worldwide totals 35.3 million/2.3 million/1.6 million total cases in 2012 new cases in 2012 deaths in 2012 Sub-Saharan Africa 25 million/1.6 million/1.2 million Caribbean 250,000/12,000/11,000 South and South-east Asia 3.9 million/270,000/220,000 Latin America 1.5 million/86,000/52,000 Eastern Europe and Central Asia 1.3 million/130,000/91,000 East Asia 800,000/270,000/220,000 North America 1.3 million/48,000/20,000 Western Europe 860,000/29,000/17,000 North Africa and Middle East 260,000/32,000/17,000 Oceania 51,000/2100/1200 Fig. 13.28 The incidence of new HIV infection is increasing more slowly in many regions of the world, but AIDS is still a major disease burden. the number of individuals living with HiV/aiDS is large and continues to grow, but the number of new infections in 2012 decreased by over one-third since the peak of the epidemic. Worldwide, in 2012, it is estimated that there were around 35.3 million individuals infected with HiV, including some 2.4 million new cases, and approximately 1.6 million deaths from aiDS, a decrease of 30% since the peak in 2005. new infections in children have declined approximately 50% since 2001, with 260,000 new cases in 2012. (AIDS Epidemic Update, unaiDS/World Health Organization, 2013.)
HIV belongs to a group of retroviruses called the lentiviruses, from the Latin lentus, meaning slow, because of the gradual course of the diseases that they cause. These viruses persist and continue to replicate for many years before causing overt signs of disease. In the case of HIV, the virus targets cells of the immune system itself, producing an initial acute infection that is controlled to the point that infection is not apparent, but rarely leading to an immune response that can prevent ongoing replication of the virus. Thus, although the initial acute infection does seem to be controlled by the immune system, HIV establishes latency within cells of the immune system and continues to replicate and infect new cells for many years. As will be discussed below, this ultimately exhausts the immune system, resulting in immune deficiency, or AIDS, that leads to opportunistic infections and/or malignancy that cause death.
Fig. 13.29 The virion of human immunodeficiency virus (HIV). the virus illustrated is HiV-1, the leading cause of aiDS. the virion is roughly spherical and measures 120 nm in diameter, or about 60 times smaller than the t cells it infects. the three viral enzymes that are packaged in the virion—reverse transcriptase, integrase, and protease—are shown schematically in the viral capsid. in reality, many molecules of these enzymes are contained in each virion. Photograph courtesy of H. Gelderblom.
gp120env RNA genome envelope protease (p10) integrase (p32) nucleocapsid reverse transcriptase (p64) lipid membrane MHC proteins matrix proteins gp41 p17gag gp120/gp41 complex, or viral spike 13-26 HIV infects and replicates within cells of the immune system.