World Population Highlights 2007: HIV/AIDS

(September 2007) The AIDS epidemic is one of the most destructive health crises of modern times, ravaging families and communities around the world. By 2006, more than 25 million people had died and at least 35 million people were living with HIV. An estimated 4.3 million people were newly infected with HIV in 2006.

Nearly 63 percent of all people with HIV worldwide live in sub-Saharan Africa—25 million people. While southern Africa has been hardest hit, other regions also face serious AIDS epidemics. In recent years, nationally representative surveys have allowed researchers to lower previously published HIV prevalence estimates for some countries. But the number of people infected and the effects on families, communities, and countries are still staggering.

HIV Prevalence Is Highest in Southern Africa

Source: C. Haub, 2007 World Population Data Sheet.

HIV/AIDS Is More Common in Less Developed Regions.

  Percent of Population Ages 15–49 With HIV/AIDS, 2005/2006
More developed regions 0.5
Less developed regions 1.1
Africa 4.5
North America 0.6
Latin America/Caribbean 0.5
Europe 0.5
Oceania 0.4
Asia 0.2

Source: C. Haub, 2007 World Population Data Sheet.

Impact on Demographics and Health

Countries hard hit by the AIDS epidemic have seen mortality surge and life expectancy drop in the last decade. But the epidemic has not led to a decrease in population in sub-Saharan Africa, due to relatively high fertility. Even accounting for AIDS-related mortality, sub-Saharan Africa’s population is projected to grow from 788 million in 2007 to 1.7 billion in 2050.

AIDS takes a major toll on societies. It ranks fourth among the leading causes of death worldwide and first in sub-Saharan Africa. In 2006, UNAIDS estimated that 2.9 million adults and children died of AIDS and 2.1 million of them were in sub-Saharan Africa.

Effects on Mortality and Life Expectancy

People living with HIV and AIDS are prone to developing other illnesses and infections because their immune systems are suppressed. The AIDS epidemic has fueled a rise in tuberculosis wherever HIV prevalence is high. In sub-Saharan Africa, death rates among children under age 5 are substantially higher than they would be without HIV. Without lifesaving drugs, one-third of children who are born infected with HIV (transmitted through their mothers) die before their first birthday, and about 60 percent die by age 5.

The surge in AIDS deaths has also halted or reversed gains in life expectancy in many African countries. For example, in Lesotho, where an estimated one in every four adults was living with HIV/AIDS in 2005, life expectancy was nearly 60 years in 1995, but plummeted to 36 years by 2007, primarily due to AIDS-related deaths.


As HIV continues to spread—in the absence of a vaccine or cure—prevention remains the key way to curb the epidemic. The most common mode of HIV transmission is sexual contact. Thus, effective prevention programs promote abstaining from sex, delaying the onset of sexual activity, staying with one mutually faithful partner, limiting the number of sexual partners, consistently and correctly using condoms, and counseling and testing for HIV. Preventing HIV transmission from mothers to their infants is also a way to save lives.

Measurement Challenges

Since 2001, a new source of data on HIV prevalence has become available for more countries: demographic and health surveys based on nationally representative samples. The Demographic and Health Survey (DHS) program, conducted by ORC Macro with national agencies, tests people for HIV. Most of the DHS surveys, along with the HIV/AIDS Indicator Surveys (AIS) completed so far, suggest HIV prevalence is likely lower than earlier estimates.

  % of HIV-Positive Adults
  Estimate at Time of DHS/AIS Year   Estimate Year
Burkina Faso 4.2 2003   1.8 2003
Cote d’Ivoire 7.1 2005   4.7 2005
Kenya 15.0 2001   6.7 2003
Zambia 21.5 2001   15.6 2001/2002

In India, a nationally representative survey found that 0.36 percent of adults ages 15 to 49 were HIV positive in 2006, compared with a non-nationally representative UNAIDS estimate of 0.9 percent in 2005.

Case In Point.

AIDS-related deaths have dramatically cut life expectancy in the most affected countries and regions. In southern Africa, home to many of the worst affected countries, life expectancy dropped from 61 years of age to 49 over the last 20 years.

AIDS reshapes the distribution of deaths by age. From 1985 to 1990, deaths in eastern Africa were clustered among young children and older adults. Adults ages 20 to 49 accounted for 16 percent of all deaths. But by 2010, that share will most likely nearly double to 29 percent of all deaths. Such large surges in deaths deplete a country of residents in their prime productive years, creating the potential for severe shocks to the economy and society.

South Africa reflects many of the changes projected for populations severely affected by AIDS. By 2015, the adult population (ages 15 and older) is projected to be smaller by 6 million people (16 percent). Deaths of large numbers of women during their reproductive years and the lower survival prospects of infected children will reduce the size of the younger population as well. The total population in South Africa in 2015 is projected to be 50 million—or 15 percent lower than in a no-AIDS scenario.


Lori S. Ashford, How HIV and AIDS Affect Populations (Washington, DC: Population Reference Bureau, 2006).

Carl Haub, 2007 World Population Data Sheet (Washington, DC: Population Reference Bureau, 2007).

Carl Haub, “Improving Data Collection Efforts to Estimate HIV/AIDS,” accessed online at, on June 20, 2007.

Peter R. Lamptey, Jami L. Johnson, and Marya Khan, “The Global Challenge of HIV and AIDS,” Population Bulletin 61, no. 1 (2006).

UNAIDS, AIDS Epidemic Update: December 2006, accessed online at, on June 28, 2007.

United Nations, World Population Prospects: The 2006 Revision (New York: United Nations, 2007).


The Status of the HIV/AIDS Epidemic in Sub-Saharan Africa

Despite the fact that sub-Saharan Africa contains only about 11 percent of the Earth’s population, the region is the world’s epicenter of HIV/AIDS. The numbers are daunting. Adult HIV prevalence is 1.2 percent worldwide (0.6 percent in North America), but it is 9.0 percent in sub-Saharan Africa. UNAIDS estimates that at the end of 2001, there were 40 million people living with HIV/AIDS, 28.5 million of them from sub-Saharan African. Five million adults and children became newly infected with HIV in 2001, 3.5 million of them from sub-Saharan Africa. Three million people died from AIDS-related causes in 2001, and 2.2 million of these deaths were among sub-Saharan Africans.2

AIDS is now the leading cause of death in sub-Saharan Africa. (Worldwide, AIDS is the fourth leading cause of death.) Life expectancy at birth has plummeted in many African countries, wiping out the gains made since independence. The combination of high birth rates and high AIDS mortality among adults, including many parents, has meant that more than 90 percent of children who have been orphaned as a consequence of the HIV/AIDS epidemic are in this region.2

These statistics disguise an important part of the story, however. Most of the worst affected countries form an “AIDS belt” in eastern and southern Africa. This belt consists of about 16 countries3 and stretches from Djibouti and Ethiopia down the east side of the continent through South Africa. These countries constitute only a little more than 4 percent of the world’s population but account for more than 50 percent of HIV infections worldwide.

According to UNAIDS, all the worst affected countries (with prevalence rates over 20 percent) are contiguous to one another in the lower part of the continent. These include South Africa, Lesotho, Swaziland, Botswana, Namibia, Zambia, and Zimbabwe. Botswana, Lesotho, Swaziland, and Zimbabwe have prevalence rates above 30 percent.4

Further north in the AIDS belt, Mozambique, Malawi, Burundi, Rwanda, Kenya, Tanzania, and Ethiopia all have adult prevalence rates in the 6-15 percent range. Adult prevalence in Uganda is estimated to be around 5 percent. Uganda is the one country in the region that has probably achieved a longstanding decline in HIV prevalence. Prevalence in Uganda may have peaked in the 12-13 percent range in the early 1990s before the onset of this decline.

Elsewhere, Somalia, Eritrea, Djibouti, and Sudan have little or no data, and Madagascar remains an interesting case. Despite tourism, an active commercial sex trade, and high rates of other sexually transmitted infections (STIs), and despite being separated from the African mainland by only 60 kms of water, adult HIV prevalence remains below 1 percent.5

Though having overall adult prevalence rates lower than in the eastern and southern parts of the continent, the middle part of Africa6 is undergoing a serious and generalized7 HIV/AIDS epidemic. Among the countries in the region, the Democratic Republic of Congo, Chad, and Equatorial Guinea show adult HIV prevalence rates under 5 percent. Angola has been war-torn and chaotic for so long that it is difficult to know exactly what is transpiring with the epidemic there. However, UNAIDS places the adult prevalence rate at 5.5 percent. Elsewhere in the region, UNAIDS reports prevalence rates of 7.2 percent in the Congo, 11.8 percent in Cameroon, and 12.9 percent in the Central African Republic.8 Many of the worst affected countries in middle Africa have the highest rates of other STIs on the continent.

Among the 15 countries of West Africa,9 only a few countries have prevalence rates over 5 percent. These include Burkina Faso (6.5 percent), Côte d’Ivoire (9.7 percent), Nigeria (5.8 percent), and Togo (6.0 percent). With an estimated population of 127 million, Nigeria is the demographic giant of sub-Saharan Africa. After South Africa, Nigeria has more people living with HIV/AIDS (3.5 million in 2001) than any other place on the continent. Côte d’Ivoire receives a large number of male migrants from neighboring countries who are temporary workers. Along with a vibrant commercial sex industry, especially in the capital city of Abidjan, this helps explain why Côte d’Ivoire has emerged as the epicenter of the epidemic in West Africa.

Table 1
Estimated Number of People in the African “AIDS Belt” Living with HIV/AIDS, end of 2001

Total Adults and Children Total Women (15-49) Adults (15-49) rate (%)
Global Total 40 million 18.5 million 1.2
Sub-Saharan Africa 28.5 million 15 million 9.0
Ethiopia 2.1 million 1.1 million 6.4
Uganda 600,000 280,000 5.0
Kenya 2.5 million 1.4 million 15.0
Tanzania 1.5 million 750,000 7.8
Rwanda 500,000 250,000 8.9
Burundi 390,000 190,000 8.3
Mozambique 1.1 million 630,000 13.0
Malawi 850,000 440,000 15.0
Zambia 1.2 million 590,000 21.5
Zimbabwe 2.3 million 1.2 million 33.7
Namibia 230,000 110,000 22.5
Botswana 330,000 170,000 38.8
Swaziland 170,000 89,000 33.4
Lesotho 360,000 180,000 31.0
South Africa 5.0 million 2.7 million 20.1

Source: UNAIDS, Report on the Global HIV/AIDS Epidemic: July 2002.

Why have rates in West Africa not soared to the levels found in the AIDS belt countries of eastern and southern Africa? If the African epidemic has its roots in the Great Lakes region, the epicenter could well have moved westward into middle and western Africa. Instead, it moved primarily southward. The question is an intriguing one and no consensus has emerged in response. Cultural and social norms may have played a role.10 For example, in countries with conservative Islamic traditions and a large proportion of Muslims in the population, sexual networking may be more circumscribed than in other countries.

Demographers John and Pat Caldwell suggest at least two additional factors. They point out that the presence of other STIs is probably the single most important factor contributing to the rapid spread of HIV. However, it is not all STIs, but especially those that cause genital ulcers that serve as an effective conduit of HIV. In West Africa, gonorrhea is the most common STI, but this is a non-ulcerative STI and an ineffective transmitter of HIV. By contrast, syphilis and chancroid are the dominant STIs in eastern and southern Africa. Both are ulcerative STIs that greatly increase the probability of HIV transmission.

Also, in most societies in West Africa, male circumcision is almost always practiced, while it is uncommon in a very large swathe of the AIDS-belt countries.11 Several studies conducted over the last decade and a half point to an association between male circumcision in some areas of sub-Saharan Africa and a reduced risk of HIV infection. However, it is still not clear whether circumcision’s apparent protective effect is due to culturally or religiously dictated behaviors — such as limiting the number of sex partners — or what the foreskin’s biological role is in male infection with HIV and other STIs.

Is the epidemic still worsening or is the situation improving? Uganda is still the only country in the region that has achieved a sustained decline in HIV prevalence. In some places — parts of Zambia, for example — prevalence appears to be dropping among the younger age groups, a possible prelude to an overall prevalence decline.

UNAIDS indicates that in 2000 the number of annual new infections went down for the first time relative to the previous year.12 While this is an encouraging trend, a drop in the annual number of new infections over a short period does not mean very much by itself. Some eventual downturn in incidence (annual new infections) would eventually occur even in the absence of any successful prevention efforts. The high levels of incidence that drove expansion of the epidemic during the 1990s could not be sustained indefinitely. This happens, in part, because prevalence levels become so high in certain high-risk groups that there is little room for expansion. A drop in incidence over a number of years is needed before it signifies a change in the overall course of the epidemic. Also, a rise in a few key but large countries — Congo and Nigeria, for example — could see incidence climbing again.

The best assessment is that, while there are some hopeful signs, overall the epidemic continues to rage throughout the Africa region. Even if prevention efforts become radically more successful in the near future than they have been, the impacts of the HIV/AIDS epidemic are going to echo for generations. If prevention, treatment, and care programs evolve at a more modest pace, it is certain that HIV/AIDS will have a profound impact on African development well into the 21st century.


  1. The Joint United Nations Programme on HIV/AIDS (UNAIDS), Report on the Global HIV/AIDS Epidemic: July 2002 (Geneva: UNAIDS, 2002).
  2. USAID, Leading the Way: USAID Responds to HIV/AIDS (Washington, DC: The Synergy Project, 2001).
  3. The definition of the AIDS belt can vary. In this case, it includes 16 contiguous countries in eastern and southern Africa with serious HIV/AIDS epidemics. The countries are Djibouti, Ethiopia, Uganda, Kenya, Tanzania, Rwanda, Burundi, Mozambique, Malawi, Zambia, Zimbabwe, Namibia, Botswana, Swaziland, Lesotho, and South Africa.
  4. UNAIDS, Report on the Global HIV/AIDS Epidemic: July 2002.
  5. UNAIDS, Report on the Global HIV/AIDS Epidemic: July 2002.
  6. Middle Africa countries include Angola, Cameroon, the Central African Republic, Chad, Democratic Republic of Congo, Congo, Equatorial Guinea, and Gabon.
  7. One definition of a generalized HIV/AIDS epidemic is that HIV has spread beyond initial subpopulations engaged in high-risk sexual behavior to the general population, as evidenced by prevalence rates of 5 percent or more in urban areas. See, for example, Confronting AIDS: Public Priorities in a Global Epidemic, A World Bank Policy Research Report (New York: Oxford University Press, 1997): 87.
  8. UNAIDS, Report on the Global HIV/AIDS Epidemic: July 2002.
  9. West African countries include Benin, Burkina Faso, Cote d’Ivoire, Gambia, Ghana, Guinea, Guinea-Bissau, Liberia, Mali, Mauritania, Niger, Nigeria, Senegal, Sierra Leone, and Togo.
  10. Leading the Way: USAID Responds to HIV/AIDS.
  11. John C. Caldwell and Pat Caldwell, “Toward an Epidemiological Model of AIDS in Sub-Saharan Africa,” Social Science History 4 (Winter 1996): 567, 576, 578-585, 592.
  12. UNAIDS, AIDS Epidemic Update: December 2000 (Geneva: UNAIDS, 2000).