Preventing and Mitigating AIDS in Sub-Saharan Africa Research and Data Priorities for the Social and Behavioral Sciences (1996) / Chapter Skim
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3 EPIDEMIOLOGY OF THE HIV/AIDS EPIDEMIC
3 EPIDEMIOLOGY OF THE HIV/AIDS EPIDEMIC
Pages 69-104
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From page 69... ...
Such biological factors may include the presence of classical STDs, male circumcision, and the viral characteristics of both HIV-1 and HIV-2 and their multiple genetic strains. In sub-Saharan Africa, many of the behavioral patterns and biological conditions that can precipitate rapid HIV transmission were present at the time HIV was introduced into selected populations.
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From page 70... ...
Not surprisingly, this speculation led many African leaders to resent the implication that Africans were to blame for AIDS. The controversy about the origin of AIDS resulted in a "backlash" and denial that HIV even existed within high-risk populations in subSaharan African countries and proved very unhelpful for designing effective prevention programs.
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From page 71... ...
The highest infection rates are usually found among men and women between 20 and 40 years old; people with STDs and tuberculosis; and, as discussed in Chapter 2, certain occupational groups, such as long-distance truck drivers, military personnel, and women employed in the commercial sex and entertainment industries (including those who work in
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From page 72... ...
. HIV infection rates of well over 80 percent have been reported for commercial sex workers in East and Central Africa (Plot et al., 1987, 1988; Quinn, 1 991 )
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From page 73... ...
By 1992, between 25 and 35 percent of pregnant women in these cities were infected. Infection rates among pregnant women rose at a much more moderate pace in Nairobi, Kenya; Bangui, the Central African Republic; and Dar es Salaam, Tanzania.
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From page 74... ...
80 90 1 00 FIGURE 3-3 HIV Seroprevalence for Commercial Sex Workers in Sub-Saharan Africa: Circa 1992. NOTE: Includes infection from HIV-1 and/or HIV-2.
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From page 75... ...
The virus may be spreading even more rapidly in Southern Africa than in West Africa. For example, in Botswana, HIV prevalence among pregnant women increased from 10 percent in 1991 to 34 percent in 1993 in Francistown, and from 6 percent in 1990 to 19 percent in 1993 in Gaborone (U.S.
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From page 76... ...
(Wagner et al., 1993; Serwadda et al., 1992~. A significant contributor to the elevated prevalence of infection in subSaharan Africa is the fact that behavioral factors associated with HIV transmission including multiple partners and impermanent relationships are generally more common among the young, this coupled with the high proportion of young adults found in sub-Saharan African countries (Anderson et al., 1991~.
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From page 77... ...
The difference in the age distribution of peak HIV prevalence between men and women occurs in the region because, on average, sexual partnerships are formed between older men and younger women (see also Chapter 23. The distortion of the urban population profile caused by male migration initially resulted in equal numbers of infected men and women (Quinn, 1994~.
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From page 78... ...
Originally identified in 1986, HIV-2 was recognized among high-risk populations such as commercial sex workers in urban centers in West Africa. While having some genetic relationship to HIV-1, in evolution HIV-2 may be more closely related to a simian immunodeficiency virus (SIV)
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From page 79... ...
The geographic pattern of HIV-2 shows a higher prevalence in West Africa and in other African countries with a Portuguese colonial history (Kanki, 1991~. Troop movements among these former Portuguese colonies and travel facilitated by cultural ties surely contributed to the spread of HIV-2 in these select countries.
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From page 80... ...
Although HIV-2 appears to have been in West Africa longer than HIV-1, levels of HIV-1 infection have now surpassed those of HIV-2 in many West African countries. For example, in a recent study in Dakar, Senegal, 1,452 registered female prostitutes were followed prospectively between 1985 and 1993 (Kanki et al., 1994~.
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From page 81... ...
HIV Seroprevalence (%) 20 15 10 ~ · HIV-1 ~ HIV-2 ~ ~1 LO 1986 1987 1988 1~ 1989 1 990 1991 1992 1993 FIGURE 3-8 HIV Seroprevalence for Pregnant Women, Abidjan, Cote d'Ivoire: 19861993.
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From page 82... ...
In another study of 278 female prostitutes from Ziguinchor, Senegal, HIV-2 seroprevalence was associated with women from Guinea-Bissau and with increased years of sexual activity. Women from Ghana and Guinea-Bissau also constituted a significant portion of study participants (commercial sex workers)
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From page 83... ...
Risk Factors in Sexual Transmission Sexual Transmission Behavioral risk factors for HIV transmission among heterosexuals include number of sex partners, frequency of unprotected intercourse, commercial sex, a history of or concurrent infection with an STD, lack of male circumcision, and anal intercourse; many women are at risk only because they have unprotected intercourse with a regular partner or spouse who is infected. Of these factors, the importance of STDs as a cofactor for HIV transmission among heterosexuals has been emphasized in a number of studies (Wasserheit, 19921.
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From page 84... ...
HIV and STDs A growing body of data suggests that HIV transmission cannot be considered in isolation from the classical STDs, principally syphilis, gonorrhea, chlamydia, chancroid, trichomoniasis, and herpes simplex virus type 2 (HSV-24. HIV shares modes of transmission and behavioral risk factors with these other STDs.
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From page 85... ...
Sewankambo, personal communication, 1995~. The older infections may have become established more uniformly over time in any one particular region; given that STDs may enhance HIV transmission, the data also suggest that STDs represent an important risk factor in a very wide segment of the African urban and rural populations.
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From page 86... ...
(1989) demonstrated a high incidence of HIV infection among men who developed genital ulcer disease after contact with a commercial sex
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From page 87... ...
. The case for non-ulcerative STDs as risk factors for HIV transmission/acquisition is less well documented.
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From page 88... ...
. Data from these trials should elucidate further the effects of STD reduction on HIV transmission among the general population and should add to our understanding of the role of individual STDs, and of symptomatic and asymptomatic infections, in HIV transmission in the community setting.
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From page 89... ...
Pelvic inflammatory disease is thought to have contributed substantially to the historical "infertility belt" of Central Africa, a region that includes Cameroon, the Central African Republic, northern Zaire, the Congo, Gabon, and parts of Uganda (Arya et al., 1973; Arya and Taber, 1975; World Health Organization Scientific Group on the Epidemiology of Infertility, 1975; Frank, 19839. Based on World Fertility Survey and Demographic Health Survey data from 17 subSaharan African countries, Larsen (1994)
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From page 90... ...
Although male infecundity may be responsible for up to one-third of all "couple" infecundity, the woman is more likely to be identified as the responsible partner and to suffer the social consequences (de Bruyn,1992~. To avoid rejection and divorce, the woman in an infertile couple may seek an outside partner to make her pregnant, feeding a vicious cycle of STD-HIV transmission.
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From page 91... ...
Ro represents the reproductive rate of infection of a particular pathogen, i.e., the number of new infections transmitted by one infected person in the susceptible population. There are three direct determinants of Ro' or the rate of spread: is, which represents the mean probability of sexual transmission per partnership D, the mean number of years an infected person remains infectious c, the average rate of new sexual partner selection per year Each of these variables can be viewed as a category that encompasses certain classes of risk factors.
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From page 92... ...
Anal intercourse Sex during menses factors that may influence either the infectiousness of or susceptibility to HIV are listed in Table 3-1. Areas with the highest HIV prevalence correspond roughly to geographic areas where most men are not circumcised (Bongaarts et al., 1989; Caldwell and Caldwell, 1993; Caldwell, 1995a, l995b; Plot et al., 1994~.
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From page 93... ...
As discussed earlier, in sub-Saharan Africa, female commercial sex workers, their male clients, truck drivers, migrant workers, and the military form the core groups of heterosexual HIV transmission, resulting in the high HIV seroprevalence and seroincidence described earlier. It should also be noted, however, that once HIV infection has achieved high levels among the general population, the role of multiple sexual partnerships and core groups in sustaining the epidemic becomes less important (Wawer et al., 1994a)
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From page 94... ...
Perinatal Transmission The second major mode of HIV transmission in Africa is perinatal, which accounts for approximately 15 to 20 percent of all AIDS cases in sub-Saharan Africa, in contrast with 5 to 10 percent worldwide (Quinn et al., 1994J. The large numbers of infected children in Africa are explained by the high proportion of women infected with the HIV virus and the large number of children each women bears.
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From page 95... ...
The problem, therefore, is that the HIV status of infants born to HIVinfected mothers cannot be ascertained until well after birth. It is possible that a new inexpensive HIV test will be developed that can reliably yield positive results only if the infant is HIV-positive when cord blood is tested, although a negative result would not mean conclusively that the infant was HIV-negative (Miles et al., 1993~.
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From page 96... ...
Where the primary causes of infant deaths are infectious diseases and malnutrition, the benefits of breastfeeding outweigh the risk of HIV transmission via breastfeeding, even for women known to be infected with HIV. However, in areas with low infant mortality rates from infectious diseases, women known to be infected with HIV should be advised to use a safe feeding alternative to breastfeeding; women whose HIV status is unknown should be advised to breastfeed (World Health Organization, 1992J.
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From page 97... ...
. HIV transmission via blood transfusion is often associated with preventable endemic tropical diseases.
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From page 98... ...
Cosmetic scarification, with its custom of using communally shared cutting utensils, is another possible mode of HIV transmission, as is tattooing with unsterilized needles. HIV transmission through the use of unsterilized paraphernalia by injecting drug users has not been documented as a major mode of HIV transmission in Africa.
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From page 99... ...
Unfortunately, social science research related to sexuality, AIDS, and STDs in Africa has most frequently been conducted in urban areas and among groups that fit the Western concept of high-risk behavior, such as commercial sex workers and the military; other groups in the general population that may also be at high risk because of elevated underlying HIV prevalence are less likely to be contacted (Udvardy, 1990~. Logistical problems associated with communitybased research have further resulted in a preponderance of urban clinic, hospital, and high-risk group studies, and more recently, community-based urban and rural serosurveys involving little or no behavioral research (Kaheru, 1989; Rwandan HIV Seroprevalence Study Group, 19894.
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From page 100... ...
Conversely, serological studies that fail to collect adequate behavioral data miss an important opportunity to assess the effects of factors such as sexual practices, sexual networks, and injecting drug use practices within given populations. There is also a growing realization that the design, execution, and analysis of clinical trials for HIV vaccines, STD control, antiretroviral drugs, and genital barrier methods/ viricides all depend on appropriate behavioral research to guide enrollment, ensure adherence to trial protocols, and permit adequate interpretation of epidemiological results (including the very basic need to control for potential differential behavioral change among study groups)
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From page 101... ...
Ethical standards related to biological and behavioral data collection, and to intervention trials of medical and behavioral prevention modalities, include voluntary informed consent, confidentiality, randomization, avoidance of physical/ psychological risk, and provision of STD/HIV counseling and preventive services (Christakis, 1988; Barry, 1988~. The concept of justice is also relevant, particularly in the case of international research: the burdens of research should be justly distributed, and disadvantaged communities should be assured of reaping an equal share of potential benefits such as access to effective vaccines that have been tested in part in developing countries (Beauchamp and Childress, 1983; Christakis, 1988; Garner et al., 1994~.
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From page 102... ...
The authors consider randomized controlled trials most appropriate for evaluating the effectiveness of behavioral interventions, but note that "it is commonly argued by behavioral researchers that random allocation to experimental groups is ethically more dubious than the uncontrolled experimentation resulting from less robust designs or from the implementation of unevaluated programs." The authors conclude that the resulting methodological weaknesses have led to a situation in which there is "a troubling lack of .
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From page 103... ...
Indeed, large population-based HIV studies in countries such as Uganda and Tanzania have adopted voluntary testing strategies, with the proviso that HIV results be made readily available and that the programs provide information and motivation for subjects to receive their results. In Nairobi, Kenya, women were tested in perinatal HIV transmission studies after giving voluntary informed consent and were given an appointment one week later to collect their results.
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From page 104... ...
More emphasis must be placed on HIV incidence studies for monitoring trends in HIV infection rates. Although seroprevalence provides important information regarding currently infected individuals in an area, measuring incidence is also critically important for estimating the rate of change in the spread of HIV infection in a given population.
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