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EPIDEMIOLOGY Current and future dimensions of the HIV/AIDS pandemic in women and children JAMES CHIN

The WHO estimates that during the first decade of the HIV/AIDS pandemic there were about 500 000 cases of AIDS in women and children, most of which have been unrecognised. During the 1990s, WHO estimates that the pandemic will kill an additional 3 million or more women and children world wide. HIV infection among heterosexual populations has been increasing throughout the world during the 1980s. AIDS has become the leading cause of death for women aged 20-40 in major cities in the Americas, Western Europe, and sub-Saharan Africa. In these cities, infant and child mortality could be as much as 30% greater than what would otherwise have been expected. During the 1990s, not only can hundreds of thousands of paediatric AIDS cases be expected, but also more than a million uninfected children will be orphaned because their HIV-infected mothers and fathers will have died from AIDS.

Introduction

By the end of the 1980s global surveillance data showed that AIDS was distributed throughout the world. In North America, Latin America, Oceania, and Western Europe there is a large number of cases in young and middle-aged men, and a small, but increasing number, in women and children. In sub-Saharan Africa, more than half of the large numbers of people with HIV infections or AIDS are women and children. This paper

provides estimates developed by the Global Programme on AIDS (GPA) of the World Health Organisation (WHO) of the current prevalence and shortterm projections of the HIV infection/AIDS pandemic as it affects women and children. In addition, estimates of the number of young uninfected children who will be orphaned by the death of their HIV-infected mothers are presented. Only HIV-1 infections are included for the purposes of this

transmission-namely, sexual, parenteral, and perinatal. Several broad though distinct epidemiological patterns of HIV infections/AIDS have been described by WHO.1.2 In pattern I areas, the primary population groups affected are homosexual men and intravenous drug users; extensive spread of HIV began in the late 1970s/early 1980s. There are not many paediatric AIDS cases in these areas since heterosexual spread of HIV, though increasing, accounts for a moderately small number of new infections. This pattern is seen in North America, Western Europe, and Oceania. In pattern II areas, HIV

infection/AIDS

is found

predominantly in sexually active heterosexuals; extensive spread of HIV probably began in the mid-to-late 1970s. Since many women of childbearing age have been infected in these areas, perinatal transmission of HIV is a major and increasing problem. Pattern IIareas are sub-Saharan Africa and some parts of the Caribbean. Many Latin American countries were initially classified as belonging to pattern I. However, by the mid-to-late 1980s, sexual transmission among heterosexuals had increased to such an extent in this region that Latin America is now classified as pattern I/II.3 Areas currently classified as pattern III include Asia, most Pacific countries (excluding Australia and New Zealand), Eastern Europe, North Africa, and the Middle East. HIV was introduced into these areas in the early-tomid 1980s. Although there is indigenous spread of the virus in most of these countries, the prevalence of both AIDS cases and HIV infections was low at the end of the 1980s with no clearly predominant mode of HIV transmission. However, the situation is changing rapidly in a few countries. During the late 1980s, the prevalence of HIV infections has greatly increased among intravenous drug users in Southeast Asia, especially in Thailand, where the prevalence is now nearly 50%; focal increases (up to 50%) have been recorded among female prostitutes in several cities in Thailand and India.3

Estimation methods HIV seroprevalence

paper.

Epidemiological patterns of

HIV

infections/AIDS Factors that

responsible for global patterns of HIV (1) time when HIV entered or began to spread extensively in the population; and (2) the relative frequency of the three modes of HIV

Serosurvey data must be interpreted and extrapolated with extreme caution because of differences in methods used

are

infection/AIDS

include:

ADDRESS: Surveillance, Forecasting and Impact Assessment Unit, Global Programme on AIDS, World Health Organisation, 1211 Geneva 27, Switzerland (J. Chin, MD)

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Fig 1-Estimated number of HIV-infected women aged 15-49 years. No in boxes = prevalence per 100 000 women. in HIV serosurveys and because HIV infections are not distributed in any population. To estimate the seroprevalence of HIV infection in females, WHO used many national or regional estimates of HIV infection in total populations together with either male/female ratios of reported AIDS cases or large community HIV serosurveys to calculate the proportion and number of HIV infections in

randomly

women.

HIV incidence in infected women Annual incidence of HIV infection in women can be derived from current seroprevalence estimates combined with the estimated time when HIV began to spread extensively in the population. For the USA and most central African countries, the late 1970s can be used as a reasonable starting point-for Western Europe the early 1980s. In Thailand, extensive spread of HIV began in 1988. Without epidemiological data, the annual incidence of infection can be estimated by the assumption that there is a linear increase from the starting point up to the most current seroprevalence estimate level. However, epidemiological data indicate that most HIV infections were acquired in the early-to-mid 1980s. Thus, the cumulative HIV infection curve for these populations from 1980 to 1989 was sigmoidal rather than linear or exponential. A sigmoidal curve was fitted from the most recent prevalence estimate of HIV infection back to the starting point of the epidemic (late 1970s or early 1980s) to calculate annual cohorts of HIV-infected women. Infected cohorts were then subdivided into age groups according to observed age distribution of HIV-infected females in the population, with

particular emphasis on women of childbearing age-iie,15 to 49 years.

HIV-infected infants To calculate the number of HIV-infected infants, the number of HIV-infected women who might give birth

during a given year must be estimated. Estimates of annual cohorts of HIV-infected women, as well as fertility patterns and rates for a given area or population, can be used to calculate the annual expected number of HIV-infected babies born to HIV-infected women as follows: (number of infected females x age-specific fertility rate) x rate of mother to fetus/infant HIV transmission. In sub-Saharan Africa an HIV transmission rate of 25% from an infected woman to her fetus/infant was used, and women who got AIDS were removed from the population at risk for pregnancy. Details of this method have been published elsewhere.6 AIDS

cases

The WHO has developed an AIDS projection model that relies on available HIV serological survey data and on annual rates of progression from HIV infection to AIDS.4 The basic data needed are: (1) the estimated number of individuals newly infected with HIV, by year, based on available HIV serosurvey data and epidemiological observations about when HIV infection first began to spread extensively in any given population; and (2) the proportion and rate at which HIV-infected persons are expected to get AIDS. The most recent data suggest that the progression rate to AIDS after acquisition of HIV does not differ much from area to area or by mode of transmission,s with the exception of paediatric AIDS, the progression of which is much more rapid than that for adults. In the WHO model, progression rates of 20% within 5 years and 50% within 10 years are used for adult case projections. No data are available beyond 10 years, but for modelling purposes it has been assumed that progression to AIDS will be about 75 % within 15 years and 95% within 20 years. Less well documented data are available about progression in children, but the following rates were used in the WHO model: 25% in the first year, 45% by the end of the second year, 60% by the end of the third year, and 80% by the end of the fourth year.

223

Projections of adult AIDS cases for less than virtually independent of the occurrence of

5 years new

are

HIV

infections because 80%-90% of adult AIDS cases expected be present in the next 4-5 years would be the result of infection already acquired, since the disease has a very long incubation period (median about 10 years). By contrast, HIV infections of women will greatly affect the numbers of HIV-infected infants and paediatric AIDS cases within the next few years. Therefore, to estimate the number of HIV-infected infants and paediatric AIDS cases at the end of 1992, the annual incidence of HIV infection in women was estimated at a slighly lower level than was recorded during the late 1980s. This assumption about the future incidence of new infections in women will need to be modified as more HIV serological data are collected. Additional details of the WHO projection model, especially for paediatric AIDS cases, have been published elsewhere.4,6

ESTIMATED NUMBER OF CUMULATIVE HIV INFECTIONS/AIDS IN WOMEN AND CHILDREN IN PATTERN II AREAS

to

Results HIV-infected women At the end of the 1980s WHO estimated that 8-10 million

people world wide were infected with HIV, and that most of these infections occurred in the early-to-mid 1980s. More detailed data have led to a downward revision of HIVinfected people in pattern I areas and an upward revision in most sub-Saharan countries from previous estimates. If the lower range of the global estimate is used with the observed male/female ratios of AIDS cases or HIV infections, a crude estimate of the total numbers of HIV infections in women by region or continent can be made. By early 1990 more than 3 million females, most of whom were of childbearing age, were infected with HIV. About 80% are in sub-Saharan Africa (fig 1). Prevalence per 100 000 women aged 15-49 years varies from about 2500 in sub-Saharan Africa to less than 5 in Eastern Europe, most of Asia, and the Pacific countries. During the late 1980s there was a consistent age distribution of HIV-infected individuals in many central African cities (5-10% of infants were HIV positive); very few 5-15-year-old children were infected with the virus; and the prevalence of HIV infection increased among sexually active young adults, with a peak at about age 35.7 Up to 40% of the 30-34-year age group in some central African cities were infected. HIV seroprevalence rates declined for those over 35. There were more HIV infections in sexually active women aged 15-24 than in men of the same age, but this difference was in some instances reversed for the older age groups. Over the entire age range there were slightly more infected women.

*Not infected but born to

an

mfected mother

was used to derive estimates of annual incidence of AIDS cases in both women and children in pattern II areas in Africa. Fig 2 shows the estimated cumulative incidence by year: up to the end of 1992, there will be more children than women with AIDS. The model estimated that by the end of 1989 there would be more than 800 000 AIDS cases in African women and nearly 300 000 paediatric AIDS cases, and that by the end of 1992, there will be more than 600 000 cases of AIDS in women, and more than 600 000 in children. During 1992 alone, nearly 300 000 AIDS cases (150 000 in women and more than 130 000 in children) are expected. As for most AIDS patients in Africa, the diagnosis of the disease in women and children in this continent will be followed by death within a year, unless substantial improvements can be achieved with newer treatments. A 10% increase in these numbers gives an approximate global estimate of AIDS cases in women and children.

projection model

Impact of AIDS on mortality rates During the early-to-mid 1990s most countries in subSaharan Africa can expect large increases in both child ( 5 years old) and adult (especially in the 20-49-year age group) mortality rates. Impact on child mortality rates (CMRs). There will be a major impact of AIDS on mortality in the first 5 years of life-ie, number of deaths per 1000 live births-in areas where a large proportion of pregnant women are infected with HIV. For example, in a population with an under-5 mortality of 100/1000 live births, and where 5 % of pregnant women are infected with HIV, the impact of a 25%

mother-to-fetus/infant transmission rate of HIV would raise the CMR to 109/1000 (assuming an 80% mortality for the HIV-infected children in the first 5 years of life). If the proportion of pregnant women infected with HIV is 10% or

HIV-infected infants At the end of the 1980s about 2-55 million females in Africa infected with HIV and they gave birth to about 2 million infants, of whom about 500 000 were estimated to have been infected with the virus. By the end of 1992, about 4 million infants will have been born to HIV-infected women and nearly a million are expected to be infected (table). A 10% increase in these numbers gives an approximate global estimate of HIV-infected infants. were

AIDS cases in Based women

women

and children

estimated annual cohorts of HIV-infected and infants in sub-Saharan Africa, the WHO on

Fig 2-Estimated cumulative number of AIDS and children in pattern II

. = women; 0 = children.

areas.

cases

in

women

224

20%

(prevalence levels seen in several central African cities during the second half of the 1980s), the CMR will increase to 118/1000 or 136/1000 live births, respectively. To put these CMR increases in perspective, the total CMR in most industrialised countries is less than 20/1000 life births. Impact on adult (20-49 years) mortality rates (AMR). The AMR in sub-Saharan countries varies from 2-5 to 10 per 1000 annually. The fairly high prevalence of HIV infection (5-10%) among sexually active adults in many central African cities during the second half of the 1980s could double or triple the AMR in these cities by the early 1990s. Adult AIDS cases and deaths could equal or exceed the expected number of deaths from all other causes in the most severely affected sub-Saharan African cities by the early 1990s. Thus, several million uninfected children will be orphaned because a large proportion of HIV-infected mothers will die of AIDS. As with HIV infections and AIDS cases, the global total of uninfected orphans can be estimated by an increase in the projected number in Africa by at least 10%.

Discussion The WHO has made global and regional estimates of HIV infection and AIDS in women and children based on the limited data available. In general when a wide range of estimates was possible the lower value was used. Thus, the WHO estimates and projections of HIV-infected women and children should be viewed as very conservative. During its first decade the HIV infection/AIDS pandemic has caused an estimated 500 000 cases of AIDS in women and children, most of which have been unrecognised. During the 1990s, WHO estimates that the pandemic will kill an additional 3 million or more women and children throughout the world. The social, economic, and demographic impacts on women and children have until now been largely neglected. Only recently has the growing magnitude of HIV infection in women and children been recognised outside a few geographic areas. Economic studies of the HIV infection/AIDS pandemic have paid little or no attention to the special problems of women, especially mothers, and children. The major reason for such neglect was that during the early 1980s most AIDS cases were in young and middle-aged men. However, during the second half of the 1980s, HIV infections among homosexual/ bisexual men have shown a decreasing trend in most areas of the world. By contrast, there has been a slow but steady increase in HIV infections among heterosexual populations: this trend has been most pronounced in Latin America, especially in the Caribbean. In sub-Saharan Africa, where heterosexual transmission has been the predominant mode of transmission since the start of the pandemic, large increases in HIV incidence continue to be recorded. In addition to increasing HIV incidence among young and middle-aged adults in urban areas, spread to rural areas has also been noted. These new HIV infections will yield increasing numbers of AIDS cases by the early-to-mid 1990s. Since more than half the AIDS patient population in pattern II countries consists of women and children, the impact of these future cases on health care systems will be enormous. This increasing clinical care burden will add to the already heavy burden of current endemic disease. In most central African cities and in some pattern I areas, such as New York City, AIDS has become the leading cause of death for women aged 20 to 40. Results from several HIV infection/AIDS models suggest that during the next few

decades, life expectancy at birth in many sub-Saharan African cities may fall by about 6 years. Infant and child mortality could be as much as 30% greater than would otherwise have been expected. Available data on the current prevalence of HIV-infected women and children are limited; accelerated efforts are needed to collect reliable data on the natural history of HIV infection in women and childen. Current estimates need to be periodically revised as additional data are gathered. Nevertheless, whatever the actual numbers are, the HIV infection/AIDS problem in women and children will doubtless become one of the major challenges to public health, health care, and social support systems world wide. REFERENCES 1. Mann 2.

3. 4. 5.

JM, Chin J, Piot P, Quinn T. The international epidemiology of AIDS. Sci Am 1988, 256: 82-89. Chin J, Mann JM. Global patterns and prevalence of AIDS and HIV infection. AIDS 1988; 2 (suppl 1): S247-S252. Sato P, Chin J, Mann JM. Review of AIDS and HIV infection: global epidemiology and statistics. AIDS 1989; 3 (suppl 1): S301-07. Chin J, Mann JM. Global surveillance and forecasting of AIDS. Bull WHO 1989; 67: 1-7. Moss AR, Bacchetti P. Natural history of HIV infection. AIDS 1989; 3:

55-61. 6. Chin J, Sankaran G, Mann JM. Mother-to-infant transmission of HIV: an increasing global problem. In: Kessel E, Awan AK, eds. Maternal and child care in developing countries. Thun, Switzerland: Ott Publishers, 1989. 7. Rwanda HIV Seroprevalence Study Group. National community-based serological survey of HIV-1 and other human retrovirus infections ina Central African country. Lancet 1989; i: 941-43.

From The Lancet Ne

quid nimis

Plain English The Lord Chief Justice Cockburn, when addressing the students of St Mary’s Hospital Medical School a year or two since, in a set address, could find, as he said, no more useful subject on which to speak with them, and through them with the medical profession, than to advise them finally to abandon the use of technical language when setting medical statements before the public. He described with force and humour the difficulties in which jurymen are involved by the habitual use by medical wimesses of phrases to which the non-medical public attach no definite sense, or a wrong meaning, or none at all.... We have frequent occasion to observe this tendency to neologism, and the avidity with which second and third rate writers especially cover a certain crudity of reasoning and obscurity of thought, or endeavour to give weight to a shallow theory, by the selection of the very longest and most technical words which the medical vocabulary will supply. This is an error to be deplored and reprobated. The best medical writers and the most distinguished practitioners are remarkable for the clearness of their diction, and for the constant avoidance of latinised terms when they can be dispensed with.... Many a man would cease to write nonsense if he would begin by writing plain English. This is useful for medical men writing for each other; it is most desirable when they are writing or speaking words which are to be scanned by non-medical persons.... Plain English is, in ninety-nine cases out of the hundred, infinitely preferable to dog-latin or barbarous greek. It is even better than a purely classical phrase derivable from either of the dead languages. Medicine has every reason to court the investigation of men of sense and education. They love to be appealed to in plain clear language. Mystery is magnificent only to the ignorant and uneducated. The man who studies to use it is by that fact under suspicion of incompetency or quackishness.

(Sept 30, 1865)

AIDS pandemic in women and children.

The WHO estimates that during the first decade of the HIV/AIDS pandemic there were about 500,000 cases of AIDS in women and children, most of which ha...
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