USA, UK and Europe , Growth and size of the epidemic

By June 1999, 702 748 adult cases of AIDS had been reported in the USA. In addition there were 8596 paediatric cases (<13 years old). Most of the cases in children (91%) occur because a patient suffered from HIV or belonged to a group at increased risk of HIV; 4% occurred through blood transfusion; 3% in children with haemophilia. Information on risk factors for the remaining 2% of the parents of these children is not complete. Adult cases in Europe totalled 234 406 by June 2000, and those in the UK 17 151 (December 2000). There are five times more people infected with HIV at any one time than have AIDS. The rate for AIDS cases varies throughout Europe, with particularly high rates in Italy, Portugal, Spain, France and Switzerland, where the commonest mode of infection is through intravenous drug use and the sharing of needles and equipment.

In North America and the UK the first wave of the epidemic occurred in homosexual men. In the UK, proportionally more homosexual men have been notified than in America: 67% of cases compared with 48% respectively. Even though infections amongst men who have sex with men still arise, an increasing proportion of new infections in the USA is occurring amongst intravenous drug users sharing needles and equipment. There is also an increase amongst heterosexuals in both the USA and the UK. Currently in the USA, 16% of cases
of AIDS have occurred amongst women, and although the commonest risk factor amongst such women is injecting drug use (42%), the next most common mode of transmission is heterosexual contact (40%).

The nature of the epidemic within the UK is changing with more heterosexual transmission. In the UK 12% of adult cases of AIDS have occurred in women, 70% of which have resulted from heterosexual intercourse. In 2000 there were more new annual infections of HIV than ever before and for the first time more occurring as a result of heterosexual sex than men having sex with men. Most heterosexually acquired infections are seen in men and women who have come from or have spent time in Sub-Saharan Africa.

The advent of an effective antibody test in 1984 has allowed for a clearer understanding of the changing prevalence and natural history of HIV infection. Surveys show that the proportion of individuals infected needs to be high before cases of AIDS start to become apparent. It also underlines the importance of health education campaigns early in the epidemic, when the seroprevalence of HIV is low. Once cases of AIDS start to appear the epidemic drives itself and a much greater effort is required in terms of control and medical care. Within countries one finds considerable variation in seroprevalence levels for HIV. Over 70% of cases of AIDS and HIV infection within the UK occur and are seen in the Thames regions (London and the surrounding area). Among different groups one also finds geographical differences. For example, the rates among drug users is higher in Edinburgh than London, and for gay men higher in London than anywhere else in the UK. This is also found in the developing world; for example, in Tanzania and Uganda, the urban level of HIV infection in men and women can be five times higher than rural rates. The use of highly active antiretroviral therapy (HAART) in resource-rich countries has resulted in an increase in life expectancy. This, in combination with the increase in new HIV infections, means that the prevalent pool of those infected, and potentially infectious, is increasing. This presents a continuing challenge for health promotion and a re-statement of the importance of safe sex techniques, particularly condom use.

Worldwide Growth and size of the epidemic

Even though North America and Europe experienced the first impact of the epidemic, infections with HIV are now seen throughout the world, and the major focus of the epidemic is in developing/resource-poor countries.

The joint United Nations programme on AIDS (UNAIDS) has estimated that by the end of 2000 there were 36.1 million people living with HIV/AIDS (34.7 million adults and 1.4 million children <15 years). The new infections during that year were 5.3 million, approximately 16,000 new infections per day.

Currently, 95% of all infections occur in developing countries and continents, the major brunt of the epidemic being seen in sub- Saharan Africa and south-east Asia. It is now recognised that cases of AIDS were first seen in Central Africa in the 1970s even though at that time it was not recognised as such. Current surveys from some
African countries show that the prevalence of infection is high amongst certain groups – 50–90% of prostitutes, up to 60–70% of those attending departments for sexually transmitted diseases and antenatal clinics. In the developing world, HIV is spread mainly by heterosexual intercourse.

At a family level, UNAIDS estimated that by the end of 1999 the epidemic had left behind a cumulative total of 13.2 million AIDS orphans (defined as those having lost their mother or both parents to AIDS before reaching the age of 15 years).

Many of these maternal orphans have also lost their father. Orphans in Zimbabwe are expected to total 1 million by 2005 and 2 million in South Africa by 2010. Traditional family structures and extended families are breaking down under the strain of HIV. Population growth and death rates are increasingly affected. Life expectancy in countries with adult prevalences of over 10% (for example Botswana, Kenya, Zimbabwe, South Africa, Zambia, Rwanda) are expected to see an average reduction in life expectancy of 17 years by 2010–2015. Young, highly productive adults die at the peak of their output, which has a considerable impact on a country’s economy.