Tropical Medicine Mission Index of Diseases About Tropical Medicine Tropical Medicine Home Page Tropical Medicine Staff

Next Page

Geographic Distribution

Infections by HIV occur worldwide; different subtypes of the virus involve different geographic areas. Currently the highest incidence of AIDS occurs in sub-Saharan Africa, Southeast Asia, and the Caribbean. Even within these broad regions there are major differences; for example, a high rate is found in Haiti, Bermuda, and the Bahamas but a low rate is reported from Cuba. The largest population affected is in Africa, where in some countries 30% of the high-risk population (ages 15 to 50) are infected. Groups such as the military, the elite, diplomats, and businessmen may have even higher rates; 85% of prostitutes in Nairobi are HIV positive. The World Bank and WHO in Africa estimate that 25% of the sub-Saharan workforce will die in the next 20 years, that the average life span, which had been increasing to 58-63 years, will fall to 47 years, and that 3 million African children will die. Worldwide perhaps 14 million children will be orphaned or without one parent, and 30% of all neonates will be HIV positive unless education is effective and treatment or prevention becomes available. The social outcome in some countries is already devastating.

Patterns of Spread

The World Health Organization has defined three patterns of spread for the AIDS epidemic. A type 1 pattern, exemplified by the United States and Western Europe, is characterized by disease spread primarily by homosexual behavior and intravenous drug abuse. A type 2 pattern, exemplified by Africa, describes primarily heterosexual spread. It has been estimated that 80% of HIV infections in East Africa are heterosexually transmitted. Homosexuality and drug abuse are rare. A type 2 pattern is also currently seen in the Caribbean and parts of Latin America, although homosexuality and drug abuse are also contributing factors in these areas. A type 3 pattern of spread occurs in areas with recent introduction of HIV by spread from countries with type 1 or type 2 patterns via blood products or sexual contact, often prostitution. The regions thus affected include Eastern Europe, North Africa, the Middle East, and Asia.

Whether AIDS is spread by homosexuals, heterosexuals, bisexuals, intravenous drug users, or transfusion of blood products, it makes little difference to the clinical course of the disease, with some notable exceptions. More important are the individual's general health and hygiene and the bacterial, viral, and parasitic cohabitants of the world in which the patient lives and has lived.


The first cases of AIDS in black Africans were identified in the 1980s, occurring in young heterosexuals with chronic wasting, opportunistic infections, and/or Kaposi's sarcoma. However, it seems probable that AIDS in Africa has a much longer history. Currently, AIDS is the most common cause of death in many African cities. The highest rates of infection worldwide are in sub-Saharan Africa, particularly Malawi, Zambia, Tanzania, Uganda, Rwanda, Burundi, and Zimbabwe. In sub-Saharan Africa, the trans-Africa highway provides an interesting lesson in social geography. The truck drivers from the coast in Tanzania and Kenya and the prostitutes along the highway form an almost unbroken chain of infection deep into the heart of Africa, from which the epidemic spreads into the countries which are supplied by the trucks. (There is an exactly similar pattern of spread by lorry drivers in India.) In Atzori's revealing Tanzanian survey, the level of HIV seroprevalence was directly correlated with the distance between the subject's home village and the nearest main road.

In Africa, the common occurrence of ulcerative venereal diseases, such as chancroid, and the lack of male circumcision increase heterosexual transmission (see below). Condom use is not favored ("no one eats a sweet with the wrapper still on"); men's dislike of condoms was the major reason for not using them, as reported by women in a study from Tanzania. In Malawi, with the highest rate of HIV infection in the world, traditional beliefs hold that women require frequent sexual intercourse, the semen acting as a vitamin to restore blood lost during menses (a proposed benefit which would be negated by condom use). Unfortunately, while initiating an educational campaign against AIDS in the new century, the President of one African country forbade mention of condoms.

Contaminated blood products, medical injections with unclean needles, and maternal-fetal spread are also important routes of transmission. Transfusion has contributed an estimated 10%-15% to AIDS transmission in Africa, particularly affecting children with malaria, women with pregnancy-related anemia, trauma victims, and patients with sickle cell disease. Improving standards in blood banking may reverse this trend. Between 5% and 15% of AIDS is perinatally transmitted.

Certain cultural practices may also promote the heterosexual spread of AIDS in Africa. There is a tradition of multiple wives or sexual partners. Networks of concurrent sexual partners, a common situation in sub-Saharan Africa, facilitate transmission. Prostitution is considered more acceptable than in some other parts of the world. Scarification (Fig. 8.1), tattooing, the rites of passage into manhood or womanhood [circumcision, female circumcision (genital mutilation), infibulation], blood letting and blood brotherhood, use of ritual and medicinal enemas given through a dirty reed or horn, and even close head or body shaving, all entail risk of transmission of HIV if, as is almost inevitable, only one instrument is shared by a group.

Fig-8.1. Traditional medical treatment of tuberculous pleurisy by scarification over the right lower chest. The chest film in the background shows a right-sided pleural effusion at the exact site the traditional healer has applied his or her treatment. Such procedures place the individual at risk for transmission of blood-borne diseases, including AIDS.

Heterosexual spread is enhanced by multiple births in rapid succession, with cervicitis, recurrent infection, and scarring. In some societies the surviving spouse after the death of her husband must free the spirit of the deceased by having sex with the nearest relative.

Intensive educational programs have been launched in almost all countries of Africa, with varying success. Knowledge is spreading ("sex is no fun if you are dead" - a high school pupil), but sometimes "knowledge is excellent: behavior is abysmal". However, there is some recent evidence that education may be changing behavior. The first report of decreasing seroprevalence of HIV-1 in Ugandan young adults, 13 to 24 years old, was published in 1995 by Mulder and colleagues. A Ugandan behavioral study published in 1997 by Asiimwe-Okiror and colleagues comparing behavioral patterns in 1989 and 1995 showed increasing condom use, a 2-year delay in the age of first sexual intercourse, and, over the same period, a 40% decline in HIV seroprevalence in women attending antenatal clinics. Similarly, a study of Tanzanian urban factory workers registered a marked decrease in those reporting sex with multiple partners as well as those reporting casual sex partners between 1991 and 1994.

Common opportunistic infections and malignancies seen in African AIDS include tuberculosis, bacteremia, cerebral toxoplasmosis, pyogenic pneumonias, cytomegalovirus, Kaposi's sarcoma, and nonspecific enteritis (see later discussion).


HIV and AIDS rates in Asia vary substantially between countries. Japan demonstrates a very low rate, with the majority of AIDS cases occurring in hemophiliacs infected by blood products produced elsewhere. Homosexuality is rare, as is intravenous drug abuse, and condoms are widely used for contraception. However, some Japanese men participate as customers in the sex trade countries of Asia such as Thailand, where a high percentage of prostitutes are infected, providing a possible avenue of infection. Korea demonstrates low levels of seropositivity in all groups. Officially reported statistics of AIDS in the People's Republic of China describe extremely low rates, but the reliability of these reports is unknown. The level of knowledge about sexually transmitted diseases appears to be low: in a 1994 survey involving rural Chinese villagers, only 18% had heard of AIDS, and only 25% and 28% respectively had heard of sexually transmitted diseases or condoms.

Hong Kong appears to have a type I or Western distribution of infections, with the majority in homosexuals and bisexuals. Pneumocystis carinii and tuberculosis are common opportunistic infections. Singapore appears to have a relatively low level of HIV infection. In Vietnam, the infected population primarily comprises male intravenous drug abusers and female sex workers. Thailand has experienced three major HIV epidemics, in intravenous drug users, sex workers, and male sexually transmitted disease (STD) patients. Efforts to limit the epidemic have been ineffective. Two-thirds of the intravenous drug abusers in Myanmar (formerly Burma) are thought to carry the virus. The three most common opportunistic infections encountered in the AIDS population in Southeast Asia are extrapulmonary tuberculosis, cryptococcosis, and Penicillium marneffei, a fungal pathogen endemic to the region.

The first cases detected in India by surveillance were in 1986. The Ministry of Health, plagued by budget cuts, is as yet poorly equipped to handle a large number of AIDS patients. An AIDS epidemic is predicted for India primarily because of the large number of prostitutes, many of whom are infected (47% in a sampling from 1997). Although only 4.4% of respondents to a 1997 Delhi survey had particiated in sex outside or before marriage, most positive respondents were males who frequently sought sex with commercial sex workers. Almost half had never used a condom during extramarital or premarital encounters. The male to female infection ratio in India is 5:1, with female cases being primarily seen in prostitutes. The typical route of infection among males is heterosexual contact with female sex workers, while in women who are not prostitutes, the most common source of infection is their husband. Large numbers of blood donors are HIV positive, particularly professional blood donors.

In the study by Chacko et al. of 61 AIDS patients in Vellore, India, the most common presenting symptoms included weight loss, fever, and chronic diarrhea, Common secondary infections included pulmonary and/or extrapulmonary tuberculosis, oropharyngeal candidiasis, and cryptococcal meningitis. Kaposi's sarcoma was not seen in any patient. The mean duration from AIDS diagnosis to death was 4.5 months. In another study, tuberculosis and candidiasis were the most common secondary infections. Secondary infections by virulent bacteria are also common, as are cryptococcosis, cryptosporidiosis, and cytomegalovirus. Although Pneumocystis carinii pneumonia was not observed in one Indian study, in another 9% of patients expired with P. carinii as a terminal infection, with a mean CD4 count of 6 cells/mm³. In a small study of interstitial pneumonia in Bombay, three of five patients were positive for P. carinii on bronchoalveolar lavage or transbronchial biopsy. Among Indian AIDS patients examined at autopsy for gastrointestinal disease, 71% of those with diarrhea yielded an organism, as compared with 29% of those without diarrhea. The most frequent pathogens were cytomegalovirus, parasites, fungi, and Mycobacterium tuberculosis. Screening of a high-risk population at a sexually transmitted disease clinic in Bombay also revealed a high incidence of HIV-2 infection, usually occurring as a co-infection with HIV-1. However, in another study by Saran and Gupta of all seropositives tested for both viruses, 31% were HIV-2 positive only. Thus, India joins the group of HIV-2 epidemic countries, which has included Western Europe, West Africa, Brazil, and the United States.

Cuba and the Caribbean

A large screening study within Cuba has revealed that the overall prevalence of infection in that country is extremely low, with higher rates in visiting foreigners and in homosexuals. Those infected are isolated to contain the epidemic.

Other Caribbean countries differ greatly from Cuba. In these countries transmission appears to be primarily homosexual, bisexual, and heterosexual, with a minor contribution of intravenous drug abuse. Bisexuality is generally believed to be common in the Caribbean because homosexuality is not well tolerated; therefore many homosexuals are married with families. Subsequent spread to the general heterosexual population has occurred, and pediatric AIDS has resulted. Further spread of HIV in the community has been promoted by cultural patterns of multiple sexual partners and a propensity for unprotected sex.

Quinn's study of 4000 women attending a prenatal clinic in Port au Prince, Haiti, demonstrated a 9.2% HIV infection rate. High rates of infection have also been seen in the English-speaking Caribbean countries such as the Bahamas and Bermuda. Co-infection with HTLV-1 may occur, and this appears to speed progression to AIDS and shorten survival. Histoplasmosis capsulatum is endemic in much of the Caribbean, and AIDS patients are at risk for disseminated disease: there are also high rates of tuberculosis.

Central and South America

In Latin America, HIV infection is most common in Brazil and Mexico. Initial infections appeared in homosexual and bisexual males with subsequent spread to the heterosexual community via bisexuals. Intravenous drug abusers contribute to spread in a limited fashion, particularly in Argentina and Brazil. Unlike Africa and Asia, prostitution does not appear to be a major factor. Mexico is an endemic area for coccidioidomycosis, and Central America is an endemic area for histoplasmosis capsulatum. Protozoal infections such as toxoplasmosis, cryptosporidiosis, and isosporiasis are common in South America. Fungal and mycobacterial infections are more common in Brazil than P. carinii or viral infections.


The pattern of HIV infection is type 1, with initial cases seen in homosexual and bisexual males in urban centers. Subsequent transmission to the heterosexual population has occurred. Education of the public and the prostitute population and increased condom use have diminished the spread of a variety of sexually transmitted diseases, including gonorrhea. Unfortunately, participation as sex tourists in Asian countries by Australian males has produced persistent seeding of penicillinase-producing strains of gonorrhea from Southeast Asia, with obvious implications for the importation of HIV. Opportunistic infections appear to be similar to those encountered in the United States, with a high prevalence of P. carinii infection and a preponderance of atypical mycobacterial infection as compared with M. tuberculosis.

Back to the Table of Contents

Copyright: Palmer and Reeder