Acquired
immunodeficiency syndrome (AIDS) and the entire spectrum of
diseases associated with human immunodeficiency virus (HIV)
infection have rapidly emerged as major global and national public
health problems. About 183,000 cases of AIDS had been reported in
152 countries, as of 30 September 1989, but the actual number is
estimated to be over three times as high. In addition,
there are estimated to be 6 to 8 million who are infected with the
virus, but do not yet show major symptoms. The latest
estimates show a continuing and even increasing spread of the
disease. WHO's projections indicate that the epidemic will continue
to grow throughout the next decade, with about 15 million new
infections expected in the early 2000s. Moreover its geographic
scope will be much wider, as the disease is already gaining
footholds in previously unaffected regions. In countries where it
is already prevalent, it is growing in hitherto lightly affected
population groups, including children and rural
communities.
As the epidemic has
been followed for only about seven years, it is not known what
proportion of the people infected with HIV will ultimately develop
the symptoms of AIDS. Current estimates are that about 50 per cent
will develop AIDS within 10 years, but the percentage that will
develop AIDS after 15 or 20 years cannot be predicted at this time,
nor can the proportions who will eventually die of the disease. The
fatality rate among those who develop symptoms appears to be high,
but many essential epide-miological characteristics,
including the natural
history of asymptomatic infections, have yet to be
elucidated. The cumulative total of AIDS cases world-wide was
projected by WHO to exceed 1 million by the early 1990s and could
exceed 3 million by the late 1990s."
AIDS is a prolonged,
physically debilitating illness that often is economically and
emotionally devastating for the victims and their families. Most of
the people with AIDS are young and middle-aged adults, whose
illness and death deprive their countries of a valuable resource.
The number of infants born with HIV infections is increasing,
particularly in some developing countries, jeopardizing these
countries' recent, hard-won gains in infant and child survival. At
present there are no very effective medical techniques for the
prevention or treatment of AIDS. Consequently, educational
campaigns to prevent it from spreading are essential while the
search for effective treatment continues. The main lines of defence
against AIDS are education to reduce high-risk behaviour and
provision of a safe blood supply for transfusions, through
screening for HIV antibodies. As with most other infectious
diseases, a fairly stable prevalence of HIV infections will
eventually be established, but how high or low that prevalence will
be will depend on the effectiveness of prevention
programmes.
The costs of the
HIV/AIDS epidemic could prove staggering for both the developed and
the developing countries. In the United States, the country with
the most reported cases, total federal expenditures on AIDS are
projected to exceed $2 billion in fiscal year 1989; the average
lifetime costs per AIDS patient in the United States are estimated
at $50,000 to $60,000. Treatment with AZT, the most effective
drug available so far for HIV/AIDS, has been costing about $8,000
per patient per year, although some selective reductions in price
have recently been offered by the manufacturer. Clearly, such costs
are beyond the means of the developing countries, where per capita
expenditure on health often does not exceed $5 annually. The
enormous cost of caring for AIDS patients threatens to divert
resources from other health programmes, with adverse consequences
for overall health and mortality.
Although the United
States has by far the largest number of reported AIDS cases,
several developing countries in the Americas and in central and
eastern Africa have a higher incidence of infection. The impact of
the disease in these countries will go beyond the normal concern of
public health authorities. Associated ethical and humanitarian
problems will increase, along with human suffering, and these
countries' economic and social development may be held back
severely unless treatments are found or a vaccine is discovered in
the next few years and made widely available. In some countries in
Africa, the incidence of infection is 10 per cent and up among the
urban adult population, both male and female, especially those
between ages 20 and 50. Workers in this age group are essential in
the more modern sectors of the economy, notably in the mining
industry in certain African countries. The incidence of infection
is also increasing rapidly in several Latin American countries, and
is beginning to surge in at least one Asian country (Thailand).
Policy-makers in countries whose key industries are about to be
seriously affected by AIDS, to a point where they might no longer
be internationally competitive, may be forced to use the limited
means available to retard the impact of the disease on the
workforce in these industries. In the case of the mining industry
in Africa, the demographic structure and traditions of health care
offer some potential for a comparatively good response to a
sustained educational effort.
While it is not yet
possible to project the long- term incidence of HIV infections and
AIDS cases with much certainty, WHO has used the available
information to estimate the impact of AIDS on mortality and
population growth in a hypothetical country. This hypothetical case
is instructive because the country has characteristics similar to
those in some central African areas, where up to 25 per cent of the
population 20 to 40 years of age in some cities were infected with
HIV in 1987. In the WHO model, the rate at which infected persons
progress to AIDS has been estimated to be 20 to 25 per cent within
5 years and close to 50 per cent within 10 years. The progression
rate for adults is projected to be 75 per cent within 15 years and
100 per cent within 20 years. The model assumes that half of the
infants born to HIV-infected mothers will be infected, and that 80
per cent of infected children will have progressed to AIDS by their
fifth birthday. Because of the high infection rates of sexually
active females in some urban areas, about 10 per cent of children
under five years old in urban areas are assumed to be infected.
Persons with AIDS are assumed to die in the same year in which the
disease develops. With a population of 20 million and an average
HIV infection prevalence of 2.3 per cent in the country as a whole,
there would be 450,000 infected people.
In the absence of
AIDS, the population would increase by about 6.5 million between
1987 and 1997. Between 1987 and 1997, there would be 479,000 deaths
from AIDS, including 320,000 urban residents (187,000 adults and
133,000 children) and 159,000 rural residents. Although the overall
effect of AIDS on population growth would be modest in the 10-year
period (population growth would be reduced by about 7 per cent
over-all), population growth would be 36 per cent less in urban
areas. Among the urban population aged 25 to 59 in 1997 (15 to 49
in 1987), the projected population increase between 1987 and 1997
would be 70 per cent less with AIDS; the under-5 age group in 1997
would have grown 50 per cent less than without AIDS. Projections
beyond 1997 would depend on the patterns of spread of the HIV
infection. If the virus were to continue to increase in urban areas
and to spread extensively in rural areas, population growth could
turn negative.