• Introduction

• The global estimates of HIV/AIDS (1999)

• The evolving picture of AIDS

• The spread of HIV

• Using epidemiology

• Questions for reflection and discussion

• Introduction

The human immunodeficiency virus (HIV) continues to spread around the world, moving into communities previously little troubled by the epidemic and strengthening its grip on areas where AIDS is already the leading cause of death in adults (defined as people aged 15-49). Estimates by the Joint United Nations Programme on HIV/AIDS (UNAIDS) and the World Health Organization (WHO) indicate that by the end of 1999 over 30 million people were infected with HIV (27 million of whom did not know their HIV status), and that 12.7 million people around the world had already lost their lives to the disease. Unless a cure is found, or life-prolonging therapy can be made more widely available, the majority of those now living with HIV will die within a decade. The virus continues to spread causing nearly 16,000 new infections a day. Indeed, HIV/AIDS is among the top ten killers world wide, and given current levels of HIV infection, it may soon move into the top five (UNAIDS/WHO Report, 1999).

• The global estimates of the HIV/AIDS epidemic as of the end of 1999 are:

The major concentration of HIV infections is in the developing world, mostly in countries least able to afford care for infected people. In fact, 86% of people with HIV live in sub-Saharan Africa and the developing countries of Asia, which between them account for less than 10% of global Gross National Product (GNP). Infection rates are rising rapidly in much of Asia, Eastern Europe and southern Africa. The picture in Latin America is mixed with prevalence in some countries rising rapidly. In other parts of Latin America and many industrialized countries, infection is falling or close to stable. This is also the case in Uganda, Thailand, and in some West African countries. Nevertheless, although the situation is improving among many groups, large numbers of new infections occur every year in these countries.

• The evolving picture of AIDS

Sub-Saharan Africa: the epidemic shifts south
Over two-thirds of all the people living with HIV in the world (nearly 21 million) live in sub-Saharan Africa, accounting for 83% of the world's AIDS deaths. An even higher proportion of the children living with HIV in the world are in Africa, an estimated 87%. There are a number of reasons for this. First, more women of childbearing age are HIV-infected in Africa than elsewhere. Second, African women have more children on average than those in other continents, so one infected woman may pass the virus on to a higher than average number of children. Third, nearly all children in Africa are breastfed. Breastfeeding is thought to account for between a third and a half of all HIV transmission from mother to child (see Fact Sheet 10). Finally, new drugs which reduce transmission from mother to child before and around childbirth are far less readily available in developing countries, including those in Africa, than in the industrialized world. In general, West Africa has seen its rates of infection stabilize at much lower levels than East and southern Africa, where the virus is still spreading rapidly, despite already high levels of infection. For example, in Botswana, the proportion of the adult population living with HIV has doubled over the last five years, with 43% of pregnant women in a major urban centre testing HIV-positive in 1997.

Asia: low infection rates but rapid spread
HIV came later to Asia, and mostly through drug injectors and sex workers. However, by 1997 HIV was well established across the continent. The countries of South East Asia, with the exception of Indonesia, the Philippines, and Laos are comparatively hard hit, as is India. While the prevalence remains low in China, they are beginning to record increasing numbers of cases. Only a few countries in the region have developed sophisticated systems for monitoring the spread of the virus, so HIV estimates in Asia often have been made on the basis of less information than in other regions. Overall, about 6.4 million people are currently believed to be living with HIV in Asia, just over 1 in 5 of the world's total. By the end of the year 2000, that proportion is expected to grow to 1 in 4. About 94,000 children now live with HIV.

Latin America and the Caribbean: most infections are in marginalized groups
The picture is fragmented in Latin America with most infections being in marginalized groups. Men having unprotected sex with men, as well as drug injectors who share needles, are the focal points of HIV infection in many countries in the region. Rising rates in women show that heterosexual transmission is becoming more prominent with the proportion being around one fifth.

Eastern Europe: drug injection drives HIV
Until 1994, mass screening of blood samples from people whose behaviour put them at risk for HIV showed extremely low levels of infection. But in the last few years, the former socialist economies of Easter Europe and Central Asia have seen infections increase around six-fold. By the end of 1997, 190,000 adults were infected. The most common form of spread is through unsafe drug injecting, and to a lesser extent through sex workers. The rise in new cases of STDs may reflect dramatic increase in unprotected sex, which indicates that the risk of HIV infection is spreading rapidly throughout the general population of Eastern Europe.

The industrialized world: AIDS is falling
In Western Europe, HIV infection rates appear to be dropping, with new infections concentrated among drug injectors in the southern countries, particularly Greece and Portugal. About 30,000 new cases were reported in 1997. Antiretroviral drugs have accounted for low mother to baby transmission. In North America 44,000 new HIV infections were reported with half that number being in injecting drug users. As in Western Europe, mother to baby transmission is rare. Although cases of HIV infections continue to rise in the industrialized world, the cases of AIDS are falling. This downturn is probably due to the new antiretroviral drug therapies which postpone the development of AIDS and prolong the lives of people living with HIV. In the United States, in some disadvantaged sections of society, AIDS continues to rise. This rise is partly due to the inaccessibility of expensive drugs, and to less successful prevention initiatives than in the predominantly well-educated, well-organized gay communities.

North Africa and the Middle East: the great unknown
Less is known about HIV infection in North Africa or the Middle East than in other parts of the world. Just over 200,000 people are estimated to be living with HIV in these countries, under 1% of the world total.

• The spread of HIV

There are no simple explanations as to why some countries are more affected by HIV than others. Poverty, illiteracy and engaging in identified risk behaviours account for much of the epidemic. People who are infected with HIV often have no symptoms of disease (see Fact Sheet 1) for many years and can infect others without realizing that they themselves are infected. Much still needs to be done to ensure better tracking of the epidemic and to find better prevention strategies and care for people living with HIV/AIDS.

•Using epidemiology

It is important that nurses and midwives understand the epidemiological statistics for HIV and AIDS at the local, national and global level. Understanding these figures helps to persuade decision makers about the magnitude of the problem while also enabling them to make informed decisions about the allocation of resources for the care and prevention of HIV.

Incidence:
refers to the number of times an event occurs in a given time, e.g. the number of new AIDS cases presenting each month or year, or the number of new HIV infections being detected during a specified period of time.

Prevalence:
means the total number of specific conditions in existence in a defined population at a precise point in time, e.g. The number of AIDS cases or number of HIV infections which have so far been reported in your own country. The systematic collection of facts (data) about disease occurrence is part of surveillance.

Collecting information from the National AIDS Programme, or visiting health centres involved in testing and counselling people would be important sources of data. Also, visiting hospitals (to assess the number of in-patients who are HIV positive), visiting sexually transmitted disease (STD) services, blood transfusion services and other facilities where people go to access HIV-related care would provide important epidemiological information about the incidence and prevalence of HIV/AIDS. The more knowledgeable that nurses/midwives are regarding the magnitude of the problem in their area, the more they can do to influence decision makers, or make informed decisions about, HIV prevention and care.