HERPES SIMPLEX VIRUS TYPE 2 (HSV-2) is the most common cause of genital infections worldwide. 1 About 22% of people aged 12 years or older in the United States are infected with HSV-2, representing a 30% increase in prevalence since the late 1970s. 2 The prevalence of HSV-2 has also been reported to be high in developing countries. 3 With the exception of rare perinatal acquisition, HSV-2 infections are acquired primarily by contact with infected secretions during a sexual encounter. 4 Hence, HSV-2 antibodies may be used as a biologic marker of sexual behavior. Improved knowledge about risk factors for HSV-2 is important in identifying populations most likely to practice high-risk sexual behaviors. This information may be used in targeting sexually transmitted disease (STD) prevention programs to the most vulnerable populations.
Research on the epidemiology of HSV-2 in Africa has been hampered by the lack of simple and inexpensive diagnostic technology. Recent advancements in type-specific serologic assays and nucleic acid amplification techniques 5 have availed diagnostic tools that can be used to estimate the prevalence and incidence of HSV-2 in developing countries where information about the burden of genital herpes in limited. In this report, we present results from a study we conducted among bar and hotel workers in the town of Moshi, in northern Tanzania. The main aim of this study was to determine the seroprevalence of HSV-2 infection and assess the association between HSV-2 and demographic characteristics, sexual behaviors, and other STDs, including HIV-1 infection.
Study Population and Sampling
We collected data from men and women working in the registered bars and hotels in eight wards in the center of Moshi, Tanzania. The detailed methods used in this study have been described elsewhere 6 and will be reviewed here briefly. We sampled study subjects in each ward proportional to the total number of workers in the bars and hotels located in that ward. In each ward, we randomly selected one bar or hotel at a time and kept on adding until we reached the required number of workers based on the predetermined sample size.
Data Collection and Study Procedures
Data were collected between June and October 2000 at the study clinic in a nearby health center. Workers were transported to the study clinic, where they received detailed information about the study aims and procedures, and those who agreed to participate provided written informed consent. A structured questionnaire was administered in a private room by interviewers to obtain information about sociodemographic characteristics, sexual behavior, and other risk factors for HSV-2. After the interviews, pretest counseling was done before blood for syphilis, HSV-2, and HIV-1 testing was collected. Later, physicians conducted a clinical examination in a private room. Urethral swab specimens were collected from men for Gram staining and the detection of Neisseria gonorrhoeae and Chlamydia trachomatis. In women, vaginal fluid pH was measured with use of a pH paper on a vaginal swab specimen obtained from the lateral and posterior fornices, and genital swab specimens were collected for the detection of Trichomonas vaginalis, Candida albicans, N gonorrhoeae, and C trachomatis.
All study participants were requested to return to the study clinic after 2 weeks for results and posttest counseling. Study subjects with treatable genital infections received treatment at no cost, based on the guidelines of the Ministry of Health of Tanzania. The study protocol was approved by the Ethical Committee of the Tanzania National AIDS Control Program, Research and Publications Committee of the Kilimanjaro Christian Medical College (KCMC), and Institutional Review Board of the Harvard School of Public Health. Genital samples were not collected from 43/309 women (13.9%) and 10/206 men (4.9%) who were not examined. For most women, nonexamination was due to the menstrual period (at the time of the interviews), not returning for a subsequent appointment, or missing the posttest counseling session. Furthermore, samples for detection of chlamydial infection were not collected from 108/309 women (35.0%) and 3/206 men (1.5%) because of the unexpected late arrival of sample collection kits.
All specimens were processed in the Department of Clinical Laboratories at KCMC. Antibodies to HSV-2 were detected by a qualitative type-specific HSV-2 enzyme immunoassay (EIA) (Premier Type Specific HSV-2 IgG ELISA; Meridian Diagnostics, Cincinnati, OH). The sensitivity and specificity of this test are 98% and 96–99%, respectively, in comparison with Western blot and culture results. 5 HIV-1 infection was diagnosed with an EIA (Murex 1.2.0; Murex Biotech Ltd, England, UK), and reactive samples were confirmed by using a second EIA (Vironostika HIV Uni-Form II plus O; Organon, Boxtel, The Netherlands). Indeterminate or conflicting results were resolved by Western blot (Bio-Rad Laboratories Ltd, Dartford, UK). T vaginalis, N gonorrhoeae, syphilis, C trachomatis, C albicans, and disturbances of vaginal flora were identified by means of standard laboratory tests, as previously described. 6 Women with severe disturbance of the vaginal flora were classified as having bacterial vaginosis, as proposed by Amsel et al. 7 This criterion is equivalent to a score of 7 to 10 for a gram-stained smear. 8
The frequency distribution of the outcome variable and of all potential predictors was analyzed initially, and extreme data values and inconsistencies were checked. We summarized the associations between HSV-2 status and predictor variables with age-adjusted odds ratios (ORs) and 95% confidence limits. Age-adjusted ORs were calculated from logistic regression models, which included age with each of the predictors. Age was grouped into five categories and entered in these models as indicator variables, as follows: 16–20 years, 21–25 years, 26–30 years, 31–35 years, and ≥36 years. To adjust for multiple risk factors simultaneously, multivariate analyses were performed with logistic regression models. 9 Observations with missing data were retained in the analyses by means of the missing indicator method. 10 Variables were entered into the models according to the level of significance in univariate analyses (P < 0.10) or if they were known or suspected to be important risk factors for HIV-1 infection. Only significant variables (P < 0.05) were retained in the final regression models. All analyses were performed with use of SPSS statistical software (SPSS, Chicago, IL).
Of 578 men and women who were invited, 541 (93.6%) agreed to participate in the study. In this report, we excluded 22 subjects (4.1%) because they were not sexually active and most information about HSV-2 predictors was not collected for them. None of these subjects were HSV-2-seropositive. We have also excluded four subjects (0.7%) who did not provide blood samples for HSV-2 testing. Out of 515 subjects with complete data, 309 (60.0%) were women and 206 (40.0%) were men. The age of study participants ranged from 16 to 66 years (mean = 29.5 years; standard deviation [SD] = 9.2 years). Men were older (mean age = 32.4 years; SD = 10.5 years) than women (mean age = 27.6 years; SD = 7.7 years;P < 0.001). The majority of both men and women had at least seven years of primary education. The sociodemographic characteristics and sexual behavior of subjects with missing STD/genital infection data were not significantly different from those of other study subjects. Of 515 subjects from whom a blood sample was taken, 224 were HSV-2-seropositive, yielding an HSV-2 seroprevalence of 43.5% (95% CI = 39.2–47.8).
The prevalence of HSV-2 in women (53.1%; 95% CI = 50.3–55.9) was higher than that in men (29.1%; 95% CI = 22.9–35.3;P < 0.0001). After adjustment for age, women were almost four times more likely to be HSV-2-seropositive than men (age-adjusted OR = 3.8; 95% CI = 2.5–5.8). In Table 1, we present the associations between selected sociodemographic characteristics, sexual behavior, and HSV-2. The prevalence of HSV-2 increased with increasing age among both men and women. The prevalence of HSV-2 was significantly higher among women than men across all age groups. The prevalence of HSV-2 decreased with increasing level of education among women (P value [test for linear trend], <0.01). In men, we observed an opposite trend, with increasing HSV-2 prevalence associated with increasing level of education (P value [test for linear trend], <0.03). For women, the risk of HSV-2 was significantly less among Catholics (age-adjusted OR = 0.4; 95% CI = 0.2–0.8) and Protestants (age-adjusted OR = 0.5; 95% CI = 0.3–0.9) than among Muslims. A surprising finding was that women who had uncircumcised sex partners had a 50% reduction in HSV-2 risk. Marital status, frequency of alcohol use, and circumcision status were not associated with HSV-2.
Most study subjects reported having more than two sex partners during the past 5 years, indicating that multiple sex partners were common in this population. Compared with the risk for women with fewer than three partners, the risk of HSV-2 more than doubled for those with three partners (age-adjusted OR = 2.4; 95% CI = 1.4–4.3) and further increased for those with at least five partners (age-adjusted OR = 4.2; 95% CI = 1.8–9.8). Similarly, the risk of HSV-2 was significantly increased among women with concurrent or overlapping partners at the time of interviews (age-adjusted OR = 3.0; 95% CI = 1.1–8.2). About two-fifths of study participants reported ever using condoms, and most of these were inconsistent users. Inconsistent condom use was associated with increased risk of HSV-2 infection among women. Women who were aware that their partners had other sex partners had a significantly increased risk of HSV-2 infection (age-adjusted OR = 2.2; 95% CI = 1.3–3.7).
In Table 2, we present the associations between HSV-2 and other STDs. Women who had an STD in the past year were more likely to be HSV-2-seropositive (age-adjusted OR = 2.3; 95% CI = 1.0–5.1). Out of 48 subjects with GUD on examination, 64.6% were HSV-2-seropositive, while 6.8% had recent or untreated syphilis. Subjects with GUD were not at increased risk of HSV-2 infection. The prevalence of chlamydial infection, gonorrhea, recent or untreated syphilis, and HIV-1 was significantly higher among women than men. After adjustment for age, women were about 10 times more likely to be HIV-1-seropositive than men (age-adjusted OR = 9.9; 95% CI = 4.8–20.3). The risk of HSV-2 was significantly higher among HIV-1-seropositive women (age-adjusted OR = 3.3; 95% CI = 1.9–6.1) than among HIV-1-negative women. The prevalence of HSV-2 was increased among men and women with chlamydial infection and recent or untreated syphilis and women with gonorrhea, although none of these values were significant. Only three women had normal vaginal flora. The risk of HSV-2 increased with increasing degree of disturbances of vaginal flora (P value [test for linear trend], <0.02).
In multivariate analyses (Table 3), age remained positively associated with HSV-2 in both women and men. The risk of HSV-2 also increased with increasing level of education in men (P value [test for linear trend], 0.05). The only other demographic characteristic associated with HSV-2 in women was religion, with a 50% HSV-2 risk reduction among Catholics in comparison with Muslims. Use of alcohol was associated with increased risk of HSV-2 infection among men, although this was significant only for men using alcohol once a week (adjusted OR = 3.0; 95% CI = 1.1–9.2). The number of sex partners in the last 5 years and having a partner who had other sex partners were associated with significantly increased risk of HSV-2 infection in women. In men, having concurrent or overlapping sex partners was associated with a threefold HSV-2 infection risk increase. For women, the only measure of STDs that remained significantly associated with HSV-2 in our final model was HIV-1 infection (adjusted OR = 2.8; 95% CI = 1.5–5.1).
The prevalence of HSV-2 and other genital infections was high, indicating that STDs were a major public health problem in our study population. HSV-2 antibodies were detected in about two-thirds of subjects with GUD. Thus, HSV-2 was the commonest STD in this population and the most frequently identified etiologic agent for GUD. Other studies conducted in Tanzania have shown high HSV-2 seroprevalence in the general population 11 and among STDs patients. 12,13 The prevalence of HSV-2 we observed in this study is consistent with results from studies conducted in other African countries. 14–19
Women were about four times more likely to be HSV-2-seropositive than men. The prevalence of other STDs, including HIV-1 infection, was also higher among women than men. Increased efficiency of HSV-2 transmission from men to women 4,20,21 and sexual behavior are known to account for increased risk of HSV-2 for women. Various studies have shown that women working in the bars and hotels in Africa have the highest rate of partner change and may work as part-time sex workers. 22,23 In our study, about one third of women had received money or gifts in exchange for sex. As observed in other studies, 2,11,15–18 age was an independent predictor of HSV-2 infection in this population. The prevalence of HSV-2 increased rapidly among young women, indicating that most women in this population acquired HSV-2 infection during the first few years of initiation of sexual activity.
Other demographic characteristics associated with HSV-2 were the level of education and religion. The risk of HSV-2 increased with increasing level of education among men. A positive association between HIV-1 and level of education among men has been reported in other studies in Africa. 24,25 Educated men with relatively higher socioeconomic status may be at increased risk of STDs because they have disposable income that may be used to support multiple sex partners. 25 The risk of HSV-2 was lower among Christian women than among Muslims, although this finding was significant only among Catholics. This association was not influenced by the circumcision status of the male partners they had in the past year. Sexual behavior might account for the observed differences in HSV-2 prevalence in association with religion. In our study, Christian women reported relatively fewer sex partners in the past 5 years than Muslims and were less likely to have concurrent partners at the time of interview. These findings are consistent with results from other studies conducted in the general population in Tanzania. 26,27
Alcohol consumption was associated with increased risk of HSV-2 among men, although this was significant only among subjects who used alcohol once a week, in comparison with nonusers. Alcohol impairs judgment and decision-making and might increase the risk of HSV-2 infection by increasing risk-taking and diminishing the perception of risk from unprotected sex. 28,29 As expected, sexual behavior was a major predictor of HSV-2 in this population. The risk of HSV-2 increased for women with increasing number of sex partners in the last 5 years and for men with concurrent or overlapping sex partners. Similar findings have been observed in other studies. 2,11,17,30,31
Women with HIV-1 infection had a significantly increased risk of HSV-2. This association was not observed among men, mainly because the prevalence of HIV-1 was low, limiting our statistical power to assess this association. We also observed increased prevalence of HSV-2 in subjects with bacterial STDs, although none of these infections were associated with significantly increased risk of HSV-2, possibly because of the low prevalence of these STDs in our study population. The positive association between HIV-1 and HSV-2 has been reported in other studies conducted in Africa. 15–17,19 Although it is not possible to determine the temporal relationship between HSV-2 and HIV-1 in our study, there is increasing evidence to suggest that infections with these viruses might reinforce each other. HIV-1 infection may facilitate HSV-2 transmission by increasing the frequency and severity of herpetic ulcers 19,32 and by enhancing the shedding of HSV-2 in the genital tract. 33–36 Numerous prospective studies have shown an increased risk of HIV-1 acquisition among HSV-2-seropositive individuals, 37 indicating that HSV-2 increases susceptibility to HIV-1.
In conclusion, HSV-2 infection was strongly associated with sociodemographic characteristics, high-risk sexual behavior, and HIV-1 infection in our study population. The high prevalence of HSV-2 infection and other genital infections among bar and hotel workers highlights the urgent need for programs to reduce the burden of STDs in this population. The strong association between HSV-2 and HIV-1 in this population suggests that HSV-2 control might be an important strategy for HIV-1 infection prevention in developing countries. Efforts to raise awareness about genital herpes and promotion of safer sexual practices continue to be the main strategies for primary prevention of HSV-2 infection. In most developing countries, secondary prevention of HSV-2 infection is hampered by the limited capacity to detect HSV-2 infections at primary health facilities and lack of suppressive antiviral therapy. Since an effective vaccine against genital herpes in not currently available, studies to assess the effectiveness of long-term suppressive therapy for prevention of both HSV-2 and HIV-1 infections among high-risk populations should be given the highest priority.
1. Nahamias AJ, Lee FK, Beckman-Nahamias S. Seroepidemiological and sociological patterns of herpes simplex virus infection in the world. Scand J Infect Dis 1990; 69: 19–36.
2. Fleming DT, McQuillan GM, Johnson RE, et al. Herpes simplex virus type 2 in the United States, 1976 to 1994. N Engl J Med 1997; 337: 1105–1011.
3. O'Farrell N. Increasing prevalence of genital herpes in developing countries: implications for heterosexual HIV transmission and STI control programs. Sex Transm Infect 1999; 75: 377–384.
4. Whitley RJ, Kimberlin DW, Roizman B. Herpes simplex viruses. Clin Infect Dis 1998; 26: 541–555.
5. Ashley RL. Sorting out the new HSV type specific antibody tests. Sex Transm Infect 2001; 77: 232–237.
6. Kapiga SH, Sam NE, Shao JF, et al. HIV-1 epidemic among female bar and hotel workers in northern Tanzania: risk factors and opportunities for prevention. J AIDS 2002; 29: 409–417.
7. Amsel R, Totten PA, Spiegel CA, et al. Non-specific vaginitis: Diagnostic criteria and microbial and epidemiological associations. Am J Med 1983; 74: 14–22.
8. Nugent RP, Krohn MA, Hillier SL. Reliability of diagnosing bacterial vaginosis is improved by a standardized method of gram stain interpretation. J Clin Microbiol 1991; 29: 297–301.
9. Hosmer DW, Lemeshow S. Applied logistic regression. New York: John Wiley & Sons, 1989.
10. Cohen J, Cohen P. Applied Multiple Regression Correlation Analysis for the Behavioral Sciences. New York: John Wiley & Sons, 1975.
11. Obasi A, Mosha F, Quigley M, et al. Antibody to herpes simplex virus type 2 as a marker of sexual risk behavior in rural Tanzania. J Infect Dis 1999; 179: 16–24.
12. Langeland N, Haarr L, Mhalu F. Prevalence of HSV-2 antibodies among STD clinic patients in Tanzania. Int J STD AIDS 1998; 9: 104–107.
13. Mwansasu A, Mwakagile D, Haarr L, Langeland N. Detection of HSV-2 in genital ulcers from STD patients in Dar es Salaam, Tanzania. J Clin Virol 2002; 24: 183–192.
14. Gray RH, Wawer MJ, Sewankambo NK, et al. Relative risks and population attributable fraction of incident HIV associated with symptoms of sexually transmitted diseases and treatable symptomatic sexually transmitted diseases in Rakai District, Uganda. AIDS 1999; 13: 2113–2123.
15. Kamali A, Nunn A, Mulder D, Van Dyck E, Dobbins J, Whitworth J. Seroprevalence and incidence of genital ulcer infections in a rural Ugandan population. Sex Transm Infect 1999; 75: 98–102.
16. McFarland W, Gwanzura L, Bassett MT, et al. Prevalence and incidence of herpes simplex virus type 2 infection among male Zimbabwean factory workers. J Infect Dis 1999; 180: 1459–1465.
17. Weiss HA, Buve A, Robinson NJ, et al. The epidemiology of HSV-2 infection and its association with HIV infection in four urban African populations. AIDS 2001; 15 (suppl 4): S97–S108.
18. Shaw M, van der Sande M, West B, et al. Prevalence of herpes simplex type 2 and syphilis serology among young adults in a rural Gambian community. Sex Transm Infect 2001; 77: 358–365.
19. Chen CY, Ballard RC, Beck-Sague CM, et al. Human immunodeficiency virus infection and genital ulcer diseases in South Africa: the herpetic connection. Sex Transm Dis 2000; 27: 21–29.
20. Langenberg AGM, Corey L, Ashley RL, Leong WP, Straus SE. A prospective study of new infections with herpes simplex virus type 1 and type 2. N Engl J Med 1999; 341: 1432–1438.
21. Mertz GJ, Benedetti J, Ashley R, Selke SA, Corey L. Risk factors for the sexual transmission of genital herpes. Ann Intern Med 1992; 116: 197–202.
22. Mgalla Z, Pool R. Sexual relationships, condom use and risk perception among female bar workers in north-west Tanzania. AIDS Care 1997; 9: 407–416.
23. Mhalu F, Hirji K, Ijumba P, et al. A cross-sectional study of a program for HIV infection control among public house workers. J AIDS 1991; 4: 290–296.
24. Dallabetta GA, Miotti PG, Chiphangwi JD, et al. High socio-economic status is a risk factor for human immunodeficiency type 1 (HIV-1) infection but not for sexually transmitted diseases in women in Malawi: implications for HIV-1 control. J Infect Dis 1993; 167: 36–47.
25. Ryder RW, Ndilu M, Hassig SE, et al. Heterosexual transmission of HIV among employees and their spouses at two large businesses in Zaire. AIDS 1990; 4: 725–732.
26. Kapiga SH, Lugalla JL. Sexual behavior patterns and condom use in Tanzania: results from the 1996 Demographic and Health Survey. AIDS Care 2002; 14: 455–469.
27. Kapiga SH. Determinants of multiple sex partners and condom use among sexually active Tanzanians. East Afr Med J 1996; 73: 435–442.
28. Morrison TC, DiClemente RJ, Wingood GM, Collins C. Frequency of alcohol use and its association with STD/HIV-related risk practices, attitudes and knowledge among an African-Am community-recruited sample. Int J STD AIDS 1998; 9: 608–612.
29. Leigh BC, Stall R. Substance use and risky sexual behavior for exposure to HIV: issues in methodology, interpretation, and prevention. Am Psychol 1993; 48: 1035–1040.
30. Smith JS, Herrero R, Munoz N, et al. Prevalence and risk factors for herpes simplex virus type 2 infection among middle-age women in Brazil and the Philippines. Sex Transm Dis 2001; 28: 187–194.
31. Potterat JJ, Rothenberg RB, Muth SQ. Network structural dynamics and infectious disease propagation. Int J STD AIDS 1999; 10: 182–185.
32. Bagdades E, Pillay D, Squire S, O'Neil C, Johnson M, Griffiths P. Relationship between herpes simplex virus ulcerations and CD4 counts in patients with HIV infection. AIDS 1992; 6: 1317–1320.
33. Mbopi-Keou F-X, Gresenguet G, Mayaud P, et al. Interactions between herpes simplex virus type 2 and human immunodeficiency virus type 1 infection in African women: opportunities for intervention. J Infect Dis 2000; 182: 1090–1096.
34. Mostad SB, Kreiss JK, Ryncarz AJ, et al. Cervical shedding of herpes simplex virus in human immunodeficiency virus–infected women: effects of hormonal contraception, pregnancy and vitamin A deficiency. J Infect Dis 2000; 181: 58–63.
35. Augenbraun M, Feldman J, Chirgwin K, et al. Increased genital shedding of herpes simplex virus type 2 in HIV-seropositive women. Ann Intern Med 1995; 123: 845–847.
36. Augenbraun M, Corey L, Reichelderfer P, et al. Herpes simplex virus shedding and plasma human immunodeficiency virus RNA levels in co-infected women. Clin Infect Dis 2001; 33: 885–890.
37. Wald A, Link K. Risk of human immunodeficiency virus infection in herpes simplex virus type 2-seropositive persons: a meta-analysis. J infect Dis 2002; 185: 45–52.