National Academies Press: OpenBook
« Previous: APPENDIX B
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

Appendix C Transmission Dynamics of Coexisting Chlamydial and HIV Infections in the United States

Marie-Claude Boily1

Introduction

Predicting HIV prevalence and incidence trends in the United States is hazardous because the mechanisms of heterosexual HIV transmission, the interrelationships between classical STDs and HIV infection, and sexual behavior among the U.S. population are not fully understood. These factors are particularly important when determining the rate of spread of HIV in different risk groups and the potential impact of STDs on heterosexual HIV transmission. Nevertheless, mathematical models of disease transmission can be used to investigate whether HIV, once introduced in the general heterosexual population, is able to establish and persist solely by heterosexual transmission, without the contribution of high-risk groups such as intravenous drug users or bisexuals. If so, how fast will HIV spread and to what extent will new HIV infections be attributable to curable STDs? A deterministic mathematical model has been developed to represent the natural course of STD and HIV infection in the general, sexually active, heterosexual population of the United States. Chlamydial infection is specifically modeled because it affects a large proportion of individuals not usually at risk for STDs and could therefore play an important role in heterosexually transmitted HIV infections, not only from high-risk to low-risk groups but also within low-risk groups. Results of the model will be discussed in relation to all curable STDs.

1  

Centre de Recherche Hôpital du St-Sacrément and Département de Médecine Sociale et Préventive, Université Laval (Center for Research, Hospital of St. Sacrement and Department of Social and Preventive Medicine, University of Laval, Quebec City, Canada).

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

Model And Parameter Assumptions

The deterministic mathematical model used, which is compartmental in structure, describes dynamically the course of both chlamydial and HIV infections in an active heterosexual population stratified by sex and sexual activity. The different stages of HIV and chlamydial infections are represented by six compartments. In the model, an individual can be susceptible to HIV, be infected with HIV but asymptomatic, or have full-blown AIDS. Each of these groups could be infected with an STD or not. Individuals can pass from one disease state to another at different rates, depending on the demographic and behavioral characteristics of the population as well as the natural history of the STD and HIV infections. The details of the model, including information on the system of nonlinear differential equations describing changes in the size of the population with time for the different disease states, are described by Boily and others (in press) in an upcoming paper.

The numerical studies of the model are based upon an initial population size of 171,481,800 individuals corresponding to the general, sexually active, heterosexual population of the United States in 1995 (Leigh et al., 1993; CIA, 1995; U.S. Census Bureau, 1996). The population growth rate is assumed to be 1.1 percent in absence of HIV infection, with a 1.01:1.00 female-to-male ratio (CIA, 1995; U.S. Census Bureau, 1996). It is assumed that an individual remains sexually active for a period of 55 years from age 15 to 70 (Anderson and Dahlberg, 1992; Leigh et al., 1993; Seidman and Rieder, 1994). Each gender is divided into six sexual activity classes to represent people with different rates of partner acquisition.

The most important assumptions when evaluating the potential impact of STDs on heterosexual HIV transmission center around HIV transmission probabilities in the absence of STDs, the sexual network and the distribution of sexual activity in the general population, the prevalence of STDs, and the nature and the magnitude of the interrelationships between STDs and HIV infection. These parameters determine whether HIV, in the presence or absence of STDs, can establish in the population and what the rate of spread of HIV in different risk groups will be. In the absence of the enhancing STD, the male-to-female per partner transmission probability for HIV is assumed to be two times that of female-to-male transmission (European Study Group on Heterosexual Transmission of HIV, 1992; Garnett and Anderson, 1993b; de Vincenzi and European Study Group on Heterosexual Transmission of HIV, 1994; Mastro et al., 1994;). In addition, HIV transmission probabilities are reduced when partnerships are formed with individuals from the high-activity classes (Jewell and Shiboski, 1990; Brookmeyer and Gail, 1994; Downs and de Vincenzi, 1996) to reflect the fact that very active individuals perform fewer acts per partnership than those with fewer partners (Garnett and Anderson, 1995; Boily and Anderson, 1996; Boily et al., in press). Lastly, different mechanisms have been postulated about

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

the way STDs interact with HIV infection (Pepin et al., 1989; Piot and Tezzo, 1990; Laga et al., 1991, 1993; Wasserheit, 1992; Wald et al., 1993; Laga, Diallo, et al., 1994; Grosskurth et al., 1995).

The interrelationship between HIV infection and chlamydial infection is defined strictly as an increase in HIV transmission probability (the relative risk) due to increased HIV susceptibility and infectivity in presence of the cofactor chlamydial (May and Anderson, 1989; Boily and Anderson, 1996). To account for the variability in the estimates from different studies (Plummer et al., 1991; Wasserheit, 1992; Laga et al., 1993; Wald et al., 1993), it was assumed that chlamydial increases HIV transmission probability by 3.6- and 5-fold. In this model, the epidemic is seeded by introducing one HIV infected person in the female activity class 6 in 1980. The annual rates of new partner acquisition of the six sexual activity classes for the model (Table C-1) were derived from different national sex surveys of the general population (Anderson and Dahlberg, 1992; Leigh et al., 1993; Laumann et al., 1994; Seidman and Rieder, 1994) that report approximately 10 percent of the general population had more than two partners in the previous year (Table C-2). The problems with such data, as with most data on sexual behavior in the general population (ACSF Investigators, 1992; Anderson and Dahlberg, 1992; Johnson et al., 1992; Leigh et al., 1993; Seidman and Reider, 1994; Laumann et al., 1994; Turner et al., 1995), are that for a variety of reasons (Morris, 1993; Wadsworth et al., 1996), men usually report more female partners than females do male partners. This is inconsistent with the fact that men and women are having sex with each other (Blower and McLean, 1991; Boily and Anderson, 1991; Morris, 1993; Wadsworth et al., 1996). Thus, for simplicity and to ensure that the mean number of sex partners between the male and female population is balanced (Blower and McLean, 1991; Boily and Anderson, 1991; Lepont and Blower, 1991), we assumed that males and females have a similar distribution in sexual activity. The simulations have been performed under an assortative mixing scenario (Garnett and Anderson, 1993b; Garnett et al., 1996) or, in other words, one where the individual prefers to choose his or her partners within the same activity class (a minimum of 44 percent of partner formation occurs within members of the same activity class). The fact that, under proportionate mixing (individuals choose their sexual partners at random, depending on availability only) (Haralosottir et al., 1992; Boily and Brunham, 1993), chlamydial and HIV infections cannot establish in the population even with a relative risk of 5 further supports this hypothesis.

The predicted HIV and AIDS trends and estimates of the fraction of cases attributable to cofactor chlamydial were produced using different sets of realistic parameter assumptions in which HIV transmission probabilities were varied depending on the magnitude of association used. The various biological and demographic parameter values used for chlamydial and HIV infection are summarized in Table C-3, and those on sexual behavior and initial chlamydial prevalence are

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

TABLE C-1 Equilibrium Prevalence of Chlamydial (the STD "Cofactor") by Sex and Sexual Activity Classes

Set 1

Females

Males

Sexual Activity Classes, i

Mean Rate of Sex Partner Change at t = 0 (per year)

Proportion in Class at t = 0 (%)

Initial Prevalence of Chlamydial (%)

Mean Rate of Sex Partner Change at t = 0 (per year)

Proportion in Class at t = 0 (%)

Initial Prevalence of Chlamydial (%)

1

0.1

86.600

0.10

0.1

88.600

0.10

2

1.1

5.500

1.59

1.1

5.500

1.48

3

2.1

3.250

3.50

2.1

3.250

3.27

4

3.2

2.425

6.58

3.2

2.425

6.16

5

6.9

1.800

7.55

6.9

1.800

7.09

6

22.0

0.355

39.27

22.0

0.355

37.53

Overall mean/prevalence

0.5

 

0.73

0.5

 

0.68

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

TABLE C-2 Distribution of General U.S. Population by Reported Number of Sex Partners in Past Year

Reported Number of Sex Partners in Past Year

Total (%)

Male (%)

Female (%)

0

18.3

13.2

22.6

1

69.0

69.1

68.9

2

5.2

5.3

5.2

3

3.1

4.6

1.8

4

1.7

2.8

0.7

5-10

2.0

3.6

0.6

11-20

0.3

0.6

0.1

21-100

0.3

0.7

0.0

>100

0.0

0.1

0.0

Total

100.0

100.0

100.0

 

SOURCE: Anderson JE, Dahlberg LL. High-risk sexual behavior in the general population. Results from a national survey, 1988-1990. Sex Transm Dis 1992;19:320-5.

TABLE C-3 Epidemiological and Demographic Parameters Used in the Simulations

Parameters

Symbols

Values

Sexually active population size in 1995

Popfemale=1.01Popmale

171,481,800

Population growth rate in absence of HIV

1.1%

Age at sexual maturation

15 yrs.

Average duration of sexual activity (taking account of background mortality) in the absence of HIV-1 infection

Dsa

55 yrs.

Perinatal transmission {probability}

30%

Life expectancy of AIDS patient

DAIDS

1 yr.

Average time from infection to the development of AIDS (incubation period) in STD-negative and -positive individuals

DHIV

10 yrs.

Average duration of chlamydial (Ct) infection in absence of treatment in HIV-negative and -positive individuals

DCt

10.2 mths

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

Parameters

Symbols

Values

Probability of HIV-1 transmission per partnership (varied)

 

Fast scenario

from female class <5 to male class <5

1ij

0.020

from female class ≥5 to male class ≥5

1ij

0.008

from male class <5 to female class <5

2ij

0.040

from male class ≥5 to female class ≥5

2ij

0.016

Probability of chlamydial transmission per partnership

 

 

from female class <5 to male class <5

1ij

0.450

from female class ≥5 to male class ≥5

1ij

0.145

from male class <5 to female class <5

2ij

0.550

from male class >5 to female class >5

2ij

0.175

Magnitude of association between chlamydial and HIV

RR

3.6 or 5

Sexual network structure or mixing pattern

kij

Assortative

Initial number of HIV infections in 1980

Female class 6

1

NOTE:

Probability of HIV-1 transmission per partnership (varied):

1ij = Probability of HIV-1 transmission per partnership from a female of activity class i to her male partner in sexual activity class j.

2ij = Probability of HIV-1 transmission per partnership from a male of class i to his female partner of sexual activity class j.

(1) = female; (2) = male; (i) = sexual activity class of the HIV-infected partner; (j) = sexual activity class of the HIV-susceptible partner.

Probability of chlamydial transmission per partnership:

1ij = Probability of chlamydial transmission per partnership from a female of activity class i to her male partner in sexual activity class j.

2ij = Probability of chlamydial transmission per partnership from a male of class i to his female partner of sexual activity class j.

(1) = female; (2) = male; (i) = sexual activity class of the chlamydial-infected partner; (j) = sexual activity class of the chlamydial-susceptible partner.

RR = relative risk of HIV transmission due to chlamydial.

kij = Probability that an individual from sex k and activity class i will choose his/her partner of the opposite sex in activity class j.

presented in Table C-1. Additional details can be found in an upcoming paper by Boily and others (in press).

Results

The predicted prevalence and incidence trends of HIV infection from 1980 to the year 2005 in the sexually active heterosexual population are depicted in (a)

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

the general population (both sexes and all sexual activity classes), (b) the low-risk group (annual rate of partner change less than one per year), and (c) the high-risk group (annual rate of partner change greater than one per year) in Figure C-1. Fast and slow spread scenarios are represented. Both are based on the parameters described in Table C-3 with a relative risk of 5 except that, for the slow scenario, HIV transmission probabilities are reduced by 25 percent.

HIV trends predicted by the model suggest that the establishment of HIV in the heterosexual population is possible and may affect a considerable proportion of the general population and different risk groups. The rate at which HIV will propagate and the maximum fraction of the population afflicted by HIV infection are highly dependent on the degree to which chlamydial infection enhances HIV transmission and on the prevalence of chlamydial infection. At the time of introduction of HIV in the population in 1980, chlamydial infection affected 0.72 percent and 0.68 percent of the general female and male population (weighted average of the different activity classes), but rates were higher in the most sexually active individuals (Table C-1), thus emphasizing their contribution to HIV transmission. Under the set of conditions investigated, HIV infection cannot establish in the absence of chlamydial infection, without a minimum degree of within-group mixing between high-activity classes or in the absence of the highest-activity class (class 6). Under the latter two conditions, chlamydial infection cannot persist either. Thus, a large fraction of HIV infections will, even over a short time period, be attributable to the cofactor chlamydial and the core group population.

The predicted fraction of the total incident heterosexual HIV and AIDS cases attributable to chlamydial infection for the periods 1980-1994 inclusive, 1995-1999, and 1995-2004 are presented in Table C-4 for the slow and fast scenarios with a relative risk of 3.6 and 5.

For all scenarios investigated, a large fraction of HIV infections can, even over a short time period, be attributed to cofactor chlamydial. For example, the model predicts that during 1990-1994, more than 86 percent and 95 percent of the heterosexual AIDS and HIV cases, respectively, could have been prevented by treating chlamydial infections.

Discussion

Despite limitations of the model due to major uncertainties concerning parameter assumptions, mathematical modeling can be used to evaluate the magnitude of the HIV/AIDS epidemic and the role of STDs in heterosexual HIV transmission. The real impact of STDs on the pattern of HIV incidence and prevalence in the United States remains uncertain because it mainly depends on the prevalence of STDs in different risk groups, the interrelationships between STD and HIV infection, the real magnitude of association, and the estimates of HIV transmission

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

FIGURE C-1 Predicted prevalence and incidence trends of HIV infection, 1980 to 2005, in the sexually active U.S. heterosexual population. Graph A represents the general population (both sexes and all sexual activity classes), with initial prevalence of chlamydial infection = 0.70 percent; Graph B depicts the low-risk group (annual rate of partner change less than one per year), with initial prevalence of chlamydial infection = 0.01 percent; and Graph C represents the high-risk group (annual rate of partner change greater than one per year), with initial prevalence of chlamydial infection = 4.63 percent. Fast and slow spread scenarios also are represented. Both are based on the parameters described in Table C-3 with a relative risk of 5 except that, for the slow scenario, HIV transmission probabilities are reduced by 25 percent.

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

TABLE C-4 Fraction of Total New HIV and AIDS Cases in the General Heterosexual Population Attributable to Cofactor Chlamydial, 1980-1994, 1995-1999, and 1995-2004

Scenarios

Slow

Fast

Parameters

 

 

 

 

Relative risk (RR):

RR = 3.6

RR = 5

RR = 3.6

RR = 5

HIV transmission probabilities:

 

 

 

 

fem. cl. <5 to male cl. <5

1ij = 0.025

1ij = 0.015

1ij = 0.030

1ij = 0.020

fem. cl. ≥5 to male cl. ≥5

1ij = 0.010

1ij = 0.006

1ij = 0.012

1ij = 0.008

male cl. <5 to fem. cl. <5

1ij = 0.050

1ij = 0.030

1ij = 0.060

1ij = 0.040

male cl. ≥5 to fem. cl. ≥5

1ij = 0.020

1ij = 0.012

1ij = 0.024

1ij = 0.016

Population Attributable Risk (%)

1980-1994:

 

 

 

 

AIDS

99

99

99

99

HIV

99

99

99

99

1995-1999:

 

 

 

 

AIDS

76

80

68

58

HIV

92

96

88

80

1995-2004:

 

 

 

 

AIDS

93

95

78

67

HIV

97

98

88

80

NOTE: See Table C-1 and C-3 for parameters and symbols.

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

probability in the absence of STDs. Additional data are needed for all these factors.

From the different scenarios considered, there are a variety of reasons to conclude that a self-sustaining HIV epidemic in the general heterosexual population is possible. First, the behavioral parameter values used underestimate the variability in sexual activity of the general population because the most sexually active individuals, who constitute a small fraction of the population, are most probably undersampled in a random sample of the general population. Greater heterogeneity in sexual activity and higher activity levels of the most active individuals are conditions that favor the establishment of an STD. Second, previous results (Garnett et al., 1992; Whitaker and Renton, 1992; Garnett and Anderson, 1993a; Boily et al., in press) show that a more assortative mixing or a majority of individuals having a low rate of partner change accentuate partner formation between high-activity classes. Thus, even with a lower level of sexual activity, a more assortative mixing would favor STD establishment and transmission. Third, chlamydial infection prevalence rates produced in the different risk groups before the introduction of HIV are lower than the rates currently reported (prevalence of chlamydial infection in young adult women and sexually active adolescents greater than 5 percent and 10 percent, men from STD clinics up to 15 to 20 percent, young asymptomatic men seen in more general medical settings greater than 3 to 5 percent). Fourth, by considering the general heterosexual population exclusively, the model does not account for the fact that many heterosexual contacts and transmissions occur with high-risk individuals such as intravenous drug users and bisexuals, for whom HIV and STD rates are higher. Fifth, if a causal relationship exists between chlamydial and HIV infections, then the magnitude of association is very likely to be underestimated (Hayes et al., 1995; Boily and Anderson, 1996). Thus, the real increase in HIV transmission probabilities per partnership or per contact due to the cofactor chlamydial could be higher than what has been reported, a relative risk of 3.6, in the best study (Laga, Alary, et al., 1994).

Two elements that have the potential to modify the global picture of HIV spread and that were not included in the model are spatial heterogeneity and the heterogeneity in HIV transmission probabilities during the long incubation period. It was assumed that the U.S. population was homogeneously distributed geographically. This implies that the rate of spread of HIV predicted may be faster than in reality, as HIV might be introduced at different times in different agglomerations. Thus, on the one hand, spatial heterogeneity could retard diffusion of HIV from one agglomeration to another and display great variability in the rate of spread between regions or districts, but it should not compromise the reproductive success of HIV infection, which was shown to be viable in a spatially homogeneous population. On the other hand, if heterogeneity in HIV transmission probabilities (with high transmission probabilities in the first and last phase of the incubation period) were included in the model, then, in its initial

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

phase, the epidemic could develop at a faster rate than predicted by the model (Blythe and Anderson, 1988).

Given a fixed trend, the effect of STD treatment on future HIV trends and the maximum proportion of HIV infections prevented are highly dependent on the degree to which STDs enhance HIV transmission, on the prevalence of STDs, and on the combination between the pattern of sexual behavior in the general population and the estimates of HIV transmission probability in the absence of STDs. The strongest assumption of this analysis is the extent to which HIV spread depends on chlamydial, since HIV cannot establish in the absence of enhancing chlamydial. This assumption is not totally unrealistic if we consider (despite other dissimilarities) that in many Northern European countries, where STDs are better controlled compared to the United States, there is little evidence of an indigenous heterosexual HIV epidemic (King K. Holmes, University of Washington, personal communication, August 1996). Thus, the model and parameters used may portray an overly optimistic scenario of the impact of chlamydial treatment on HIV incidence trends, because the model suggests that heterosexually transmitted HIV could in theory be eradicated if chlamydial were eliminated. Note that even if HIV could establish in the absence of chlamydial, a considerable fraction of HIV cases could still be attributed to cofactor chlamydial. HIV spread would slow down, but would not be eradicated by effective STD treatment alone. In addition, in the United States, the continued force of heterosexual transmission from intravenous drug use would remain. Note also that even if chlamydial infection accounts for a large fraction of new HIV cases in this model, this does not preclude the possibility that other STDs have also contributed to the spread of HIV once it has become established. The model with chlamydial is equivalent to assuming that all STDs are required for HIV to establish. Under this assumption, the eradication of heterosexually transmitted HIV is possible by eliminating only one curable STD or by reducing the prevalence of all curable STDs below a certain threshold. Another way the same HIV epidemic could be established is by assuming that it requires the presence of only one STD, such as chlamydial. This scenario is more conservative regarding the impact of STD treatment on HIV incidence trends, since the elimination of HIV would require the eradication of all STDs or the reduction of the prevalence of all curable STDs below a threshold much lower that that for the first scenario.

Despite the depressing forecast of the model on the potential impact of chlamydial infection and other STDs on HIV spread in the general U.S. heterosexual population, one optimistic point emerges from this study. This is the important fraction of heterosexually transmitted HIV infections that can be prevented by treating chlamydial infection and other curable STDs. Simulation work confirms previous results (Hethcote and Yorke, 1984) showing that screening high-risk individuals or core groups can be much more efficient than the screening of the more general population (Hethcote and Yorke, 1984; Brunham and

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

Plummer, 1990; Garnett and Anderson, 1995), because the noncore population contributes relatively little to the reproductive success of STDs and HIV infection. Thus, a 50 percent reduction in chlamydial (from 10 to 5 percent), such as observed in Region X of the United States (DeLisle et al., 1993) following the implementation of a chlamydial screening program in family planning clinics, could play an important role in slowing HIV transmission in the area. Moreover, treating STDs offers a complementary approach to interventions to change sexual behavior (such as reduction of sexual activity). Furthermore, changes in sexual behavior can produce pernicious effects by modifying the structure of social networks (Boily and Anderson, 1990; Thompson Fullilove, 1995).

Considering the great heterogeneity in seroprevalence rates of infection between regions (CDC, 1994, 1995), it can be assumed that the HIV epidemic in the heterosexual population in most U.S. states and cities might still be in its early stages (i.e., anywhere between 1980 and 2000 on our time scale). Results indicate that improved efforts to contain and prevent STDs should be made immediately and that such efforts could prevent, if initiated early enough, many new HIV infections, even over a relatively short time period. However, since exposure of the general heterosexual population to HIV via high-risk individuals such as intravenous drug users or bisexuals has not been included in the model (deliberately done in order to remain conservative), one should bear in mind that constant introduction of the virus in the general heterosexual population by these high-risk groups can always occur despite excellent STD control. Therefore, it is important when designing prevention strategies for the general heterosexual population not to ignore these remaining reservoirs of STDs, including HIV infection.

References

ACSF (Analyse des Comportements Sexuels en France) Investigators. AIDS and sexual behavior in France. Nature 1992;360:407-9.

Anderson JE, Dahlberg LL. High-risk sexual behavior in the general population. Results from a national survey, 1988-1990. Sex Transm Dis 1992;19:320-5.


Blower SM, McLean AR. Mixing ecology and epidemiology. Proc R Soc Lond B 1991;245:187-92.

Blythe SP, Anderson RM. Variable infectiousness in HIV transmission models. IMA J Math App Med Biol 1988;5:181-200.

Boily M-C, Anderson RM. Assessing change in sexual behavior using mathematical models: the impact of sexual mixing (Part A). Proceedings of the International Conference on Assessing AIDS Prevention, October 29-November 1, 1990; Montreux, Switzerland [abstract no. C2.4].

Boily M-C, Anderson RM. Sexual contact patterns between men and women and the spread of HIV-1 in urban centers in Africa. IMA J Math App Med Biol 1991;8:221-47.

Boily M-C, Anderson RM. Human immunodeficiency virus transmission and the role of other sexually transmitted diseases: measures of association and study design. Sex Transm Dis 1996;23:312-30.

Boily M-C, Brunham RC. The impact of HIV and other STDs on human populations. Are predictions possible? Inf Dis Clin North Am 1993;7:771-91.

Boily M-C, Desai KN, Garnett GP. Transmission dynamics of co-existing chlamydial and HIV infections in the heterosexual population of the United States . IMA J Math Appl Med Biol, in press.

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

Brookmeyer R, Gail MH. Risk factors for infection and the probability of HIV transmission. In: AIDS epidemiology-a quantitative approach. New York: Oxford University Press, 1994:19-50.

Brunham RC, Plummer AA. A general model of sexually transmitted disease epidemiology and its implications for control. Sex Transm Dis 1990;74:1339-52.

CDC (Centers for Disease Control and Prevention). National HIV serosurveillance summary: results through 1992. Atlanta: U.S. Department of Health and Human Services, 1994:3:51.

CDC. HIV/AIDS surveillance report, U.S. HIV and AIDS cases reported through December 1995. Atlanta: U.S. Department of Health and Human Services, 1995;5:38.

CIA (Central Intelligence Agency). CIA World Factbook. http://www.odci.gov/cia/publications/95fact/us.html, 1995.


DeLisle S, Fine D, Kaetz S, Johnson RE, Schrader M, Lee V, et al. A multi-site model for the prevention and control of sexually transmitted chlamydial infections. Tenth International Meeting of the International Society for STD Research, August 29-September 1, 1993, Helsinki [abstract no. 162].

de Vincenzi I, European Study Group on Heterosexual Transmission of HIV. A longitudinal study of human immunodeficiency virus transmission by heterosexual partners. N Engl J Med 1994;331:341-6.

Downs AM, de Vincenzi I. Probability of heterosexual transmission of HIV: relationship to the number of unprotected sexual contacts. European Study Group in Heterosexual Transmission of HIV [see comments]. J Acquire Immune Defic Syndr Hum Retrovir 1996;11:388-95.


European Study Group on Heterosexual Transmission of HIV. Comparison of female to male and male to female transmission of HIV in 563 stable couples. Br Med J 1992;304:809-13.


Garnett GP, Anderson RM. Contact tracing and the estimation of sexual mixing patterns: the epidemiology of gonococcal infection. Sex Transm Dis 1993a;20:181-91.

Garnett GP, Anderson RM. Factors controlling the spread of HIV in heterosexual communities in developing countries: patterns of mixing between different age and sexual activity classes. Phil Trans R Soc Lond B 1993b;342:137-59.

Garnett GP, Anderson RM. Strategies for limiting the spread of HIV in developing countries: conclusions based on studies of the transmission dynamics of the virus. J Acquire Immune Defic Syndr Hum Retrovirol 1995;9:500-13.

Garnett GP, Hughes JP, Anderson RM, Stoner BP, Aral SO, Whittingham WL, et al. Sexual mixing patterns of patients attending sexually transmitted disease clinics. Sex Transm Dis 1996;23:248-57.

Garnett GP, Swinton J, Brunham C, Anderson RM. Gonococcal infection, infertility, and population growth: the influence of heterogeneity in sexual behavior. IMA J Math Appl Med Biol 1992;9:127-44.

Grosskurth H, Mosha F, Todd J, Mwijarubi E, Klokke A, Senkoro K, et al. Impact of improved treatment of sexually transmitted diseases on HIV infection in rural Tanzania: randomized controlled trial [see comments]. Lancet 1995;346:530-6.


Haralosottir S, Gupta S, Anderson RM. Preliminary studies of sexual networks in a male homosexual community in Iceland. J Acquire Immune Defic Syndr 1992;5:374-81.

Hayes RJ, Schulz KF, Plummer FA. The cofactor effect of genital ulcers on the per-exposure risk of HIV transmission in sub-Saharan Africa. J Trop Med Hyg 1995;98:1-8.

Hethcote HW, Yorke JA. Gonorrhea transmission dynamics and control. In: Levin S, ed. Lecture notes in biomathematics. New York: Springer-Verlag, 1984:56:99.


Jewell NP, Shiboski SC. Statistical analysis of HIV infectivity based on partner studies. Biometrics 1990;46:1133-50.

Johnson AM, Wadsworth J, Wellings K, Bradshaw S, Field J. Sexual lifestyles and HIV risk. Nature 1992;360:410-2.

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×

Laga M, Alary M, Nzilambi N, Manoka AT, Tuliza M, Behets F, et al. Condom promotion, sexually transmitted treatment, and declining incidence of HIV-1 infection in female Zairian sex workers. Lancet 1994;344:246-8.

Laga M, Diallo MO, Buv A. Inter-relationship of sexually transmitted diseases and HIV: where are we now? AIDS 1994;8[1 Suppl]:S119-S124.

Laga M, Manoka A, Kivuvu M, Malele B, Tuliza M, Nzila N, et al. Non-ulcerative sexually transmitted diseases as risk factors for HIV-1 transmission in women: results from a cohort study. AIDS 1993;7:95-102.

Laga M, Nzilambi N, Goeman J. The interrelationships of sexually transmitted diseases and HIV infection: implication for the control of both epidemics in Africa. AIDS 1991;5[1 Suppl]:S55-S65.

Laumann EO, Gagnon JH, Michael RT, Michaels S. The social organization of sexuality: sexual practices in the United States. Chicago: University of Chicago Press, 1994:718.

Leigh BC, Temple MT, Trocki KF. The sexual behavior of U.S. adults: results from a national survey. Am J Public Health 1993;83:1400-8.

Lepont F, Blower SM. The supply and demand dynamics of sexual behavior: implications of heterosexual HIV epidemics. J Acquire Immune Defic Syndr 1991;4:987-99.


Mastro TD, Satten GA, Nopkesorn T, Sangkharomya S, Logini IM Jr. Probability of female-to-male transmission of HIV-1 in Thailand [see comments]. Lancet 1994;343:204-7.

May RM, Anderson RM. Heterogeneities, cofactors and other aspects of the transmission dynamics of HIV/AIDS. J Acquire Immune Defic Syndr 1989;2:33-67.

Morris M. Telling tails explain the discrepancy in sexual partner reports. Nature 1993;365:437-40.


Pepin J, Plummer FA, Brunham RC, Piot P, Cameron CW, Ronald AR. The interaction of HIV infection and other sexually transmitted diseases. AIDS 1989;3:3-9.

Piot P, Tezzo R. The epidemiology of HIV and other sexually transmitted infections in the developing world. Scan J Inf Dis Suppl 1990;69:89-97.

Plummer FA, Simonsen JN, Cameron DW, Ndinya-Achola JO, Kreiss JK, Gakinya MN, et al. Cofactors in male-female transmission of human immunodeficiency virus type 1. J Infect Dis 1991;163:233-9.


Seidman SN, Rieder RO. A review of sexual behavior in the United States. Am J Psychiatry 1994;151:330-41.


Thompson Fullilove M. Risk behaviors and STD/HIV transmission. Paper presented at the Institute of Medicine workshop ''Understanding the relationship of STD control to HIV prevention in the United States." Committee on Prevention and Control of Sexually Transmitted Diseases, National Academy of Sciences, Washington, D.C., July 10, 1995.

Turner CF, Danella RD, Rogers SM. Sexual behavior in the United States, 1930-1990: trends and methodological problems. Sex Transm Dis 1995;22:173-90.


U.S. Census Bureau. http://www.census.gov/, 1996.


Wadsworth J, Johnson AM, Wellings K, Field J. What's in a mean? An examination of the inconsistency between men and women in reporting sexual partnerships. J R Statist Soc A 1996; 59[Part 1]:111-23.

Wald A, Corey L, Handsfield HH, Holmes KK. Influence of HIV infection on manifestations and natural history of other sexually transmitted diseases. Ann Rev Public Health 1993;14:19-42.

Wasserheit JN. Interrelationships between immunodeficiency virus infection and other sexually transmitted diseases . Sex Transm Dis 1992;19:61-5.

Whitaker L, Renton AM. A theoretical problem of interpreting the recently reported increase in homosexual gonorrhoeal. Eur J Epidemiol 1992;8:187-91.

Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 316
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 317
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 318
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 319
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 320
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 321
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 322
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 323
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 324
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 325
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 326
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 327
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 328
Suggested Citation:"APPENDIX C." Institute of Medicine. 1997. The Hidden Epidemic: Confronting Sexually Transmitted Diseases. Washington, DC: The National Academies Press. doi: 10.17226/5284.
×
Page 329
Next: APPENDIX D »
The Hidden Epidemic: Confronting Sexually Transmitted Diseases Get This Book
×
Buy Hardback | $59.95 Buy Ebook | $47.99
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

The United States has the dubious distinction of leading the industrialized world in overall rates of sexually transmitted diseases (STDs), with 12 million new cases annually. About 3 million teenagers contract an STD each year, and many will have long-term health problems as a result. Women and adolescents are particularly vulnerable to these diseases and their health consequences. In addition, STDs increase the risk of HIV transmission.

The Hidden Epidemic examines the scope of sexually transmitted infections in the United States and provides a critical assessment of the nation's response to this public health crisis. The book identifies the components of an effective national STD prevention and control strategy and provides direction for an appropriate response to the epidemic. Recommendations for improving public awareness and education, reaching women and adolescents, integrating public health programs, training health care professionals, modifying messages from the mass media, and supporting future research are included.

The book documents the epidemiological dimensions and the economic and social costs of STDs, describing them as "a secret epidemic" with tremendous consequences. The committee frankly discusses the confusing and often hypocritical nature of how Americans deal with issues regarding sexuality—the conflicting messages conveyed in the mass media, the reluctance to promote condom use, the controversy over sex education for teenagers, and the issue of personal blame.

The Hidden Epidemic identifies key elements of effective, culturally appropriate programs to promote healthy behavior by adolescents and adults. It examines the problem of fragmentation in STD services and provides examples of communities that have formed partnerships between stakeholders to develop integrated approaches.

The committee's recommendations provide a practical foundation on which to build an integrated national program to help young people and adults develop habits of healthy sexuality.

The Hidden Epidemic was written for both health care professionals and people without a medical background and will be indispensable to anyone concerned about preventing and controlling STDs.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    Switch between the Original Pages, where you can read the report as it appeared in print, and Text Pages for the web version, where you can highlight and search the text.

    « Back Next »
  6. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  7. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  8. ×

    View our suggested citation for this chapter.

    « Back Next »
  9. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!