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EarthAt the close of this past decade, an estimated 33.6 million men, women, and children worldwide were infected with the human immunodeficiency virus (HIV). This virus, unknown until 17 years ago, now dominates national and international affairs. The HIV/AIDS epidemic is now acknowledged to be a contributing factor to changing national economies, to population displacement, and most recently, to national and international security.

The following list highlights key findings from the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) as of December 1999.

  • 32.4 million adults and 1.2 million children will be living with HIV by the end of 1999. While this is a modest increase in comparison with the global HIV totals published at the end of 1998, the WHO states that the true increase is larger due to improved surveillance. Infections in a few populous countries of Latin America and Asia were overestimated in 1998, hence the difference.

  • It is estimated that in 1999, approximately 5.6 million people became infected with HIV worldwide.

  • The highest death rate from HIV/AIDS to date, 2.6 million in 1999, is a higher global total than in any year since the beginning of the epidemic -- in spite of new antiretroviral therapies shown to extend survival, which are widely available in wealthier countries.

  • With the HIV positive population expanding rapidly, the annual number of AIDS deaths can be expected to increase for many years before peaking. If prevention programs managed to eliminate new infections, deaths among those already infected would continue mounting for some years.

  • HIV has had an unprecedented impact on an important population demographic: young, sexually active adults. Approximately one-half of all people who acquire HIV become infected before they turn 25 and typically die of one of the life-threatening opportunistic infections (OIs) associated with AIDS before they reach 35 years of age.

  • As a result of this age-associated epidemic, children are highly impacted. The WHO estimates that as of 1999, there was a cumulative total of 11.2 million AIDS orphans, defined as those having lost their mothers before reaching the age of 15. Many of these maternal orphans have also lost their fathers to AIDS.

  • In 1999, an estimated 570,000 children aged 14 or younger became infected with HIV. Over 90% were babies born to HIV positive women; these babies acquired the virus either at birth or through their mother's breast milk. Approximately 90% of these pediatric infections occurred in Sub-Saharan Africa.

  • The overwhelming majority of people with HIV -- some 95% of the global total -- live in the developing world. That proportion is set to grow even further as infection rates continue to rise in countries where poverty, poor public health systems, and limited resources for prevention and care fuel the spread of the virus.

Regional HIV/AIDS Statistics and Features,
December 1998
 Epidemic startedAdults & children living with HIV/AIDSAdults & children newly infected with HIVAdult prevalence rate [1]% HIV-
positive women
Main mode of transmission for those living with HIV/AIDS [2]
Saharan Africa
late 70s-
early 80s
North Africa & Middle Eastlate 80s210,00019,0000.13%20%IDU, Heterosexual
South & South-
East Asia
late 80s6.7
East Asia & Pacificlate 80s560,000200,0000.068%15%IDU, Heterosexual, MSM
Latin Americalate 70s-
early 80s
160,0000.57%20%MSM, IDU, Heterosexual
Caribbeanlate 70s-
early 80s
330,00045,0001.96%35%Heterosexual, MSM
Eastern Europe & Central Asiaearly 90s270,00080,0000.14%20%IDU, MSM
Western Europelate 70s-
early 80s
500,00030,0000.25%20%MSM, IDU
North Americalate 70s-
early 80s
890,00044,0000.56%20%MSM, IDU, Heterosexual
Australia & New Zealandlate 70s-
early 80s
12,0006000.1%5%MSM, IDU
Total 33.4 million5.8 million1.1% average43% average 
  1. The proportion of adults (15-49 years of age) living with HIV/AIDS in 1998, using 1997 population numbers
  2. IDU: transmission through injection drug use; MSM: sexual transmission among men who have sex with men


Twenty years into the HIV/AIDS epidemic, much is known about preventing HIV infection. Yet the epidemic continues and is in fact unrelenting in some places. Worldwide, surveillance and prevention responses vary as a result of many factors.

This article cannot provide a full description of all aspects of the epidemic in every country or the vast and diverse range of cultural, social, environmental, biological, and even political dynamics of this devastating epidemic. Instead, this article will provide a snapshot of some of that diversity and range by describing the epidemiology (i.e., frequency, distribution, and behavior) of HIV in a few representative regions and countries.

The HIV/AIDS epidemic is fraught with paradox and true drama: life-saving treatments bring hope as well as risk; countries that share borders have vastly different epidemics. HIV has changed the world and is still changing it.

Antiretroviral Therapies Significantly Impact Mortality

The numbers of new AIDS cases and AIDS deaths are both falling significantly in countries that provide antiretroviral therapy for a majority of those diagnosed with HIV. However, there is no sign that new HIV infections are following the same downward course. On the contrary, extremely worrying recent evidence suggests that the advent of life-prolonging therapies may have led to complacency among some groups of people about the dangers of HIV, and that that complacency may be leading to rises in risky behavior.

For the past several years in San Francisco, for example, there have been decreases in the number of men who have sex with men (MSM) reporting consistent condom use, increases in the number of men reporting unprotected anal sex with multiple partners, and increases in rectal gonorrhea. Many of the men sampled in these studies reported that they did not know their partners' HIV status. Of particular concern is that the absolute number of HIV positive people is probably growing because of improved survival.

Theoretically, antiretroviral therapy could reduce a person's infectiousness, or the likelihood that an infected person might pass on the virus to a sexual partner. Evidence of this effect is not conclusive, but some new research has demonstrated reduced transmission in a study of serodiscordant heterosexual couples (i.e., those in which only one partner is HIV positive). On the other hand, even if a person's overall infectiousness is reduced by anti-HIV drugs, there is good evidence that viable virus (i.e., virus capable of reproducing) can be recovered from seminal fluid in men taking highly active antiretroviral therapy, or HAART.

Yet until further studies of HIV treatment and infectivity are done, it must be assumed that a higher level of HIV in the pool of potential sexual partners means a higher risk of transmission whenever unprotected sex occurs with a partner of unknown HIV status. More than ever, prevention leaders, community-based organizations, and public health officials must continue to pursue effective HIV prevention efforts in communities where HIV incidence (number of new infections) has declined and prevalence (infection levels) is stable or increasing.

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