HIV/AIDS trends in the United States depict a concentrated epidemic with hot spots that vary by location, poverty, race/ethnicity, and transmission mode. HIV/AIDS is a leading cause of death among US women of color; two-thirds of new infections among women occur in black women, despite the fact that black women account for just 14% of the US female population. The gravity of the HIV epidemic among US women is often not appreciated by those at risk and by the broader scientific community. We summarize the current epidemiology of HIV/AIDS among US women and discuss clinical, research, and public health intervention components that must be brought together in a cohesive plan to reduce new HIV infections in US women. Only by accelerating research and programmatic efforts will the hidden epidemic of HIV among US women emerge into the light and come under control.
From the *University of Medicine and Dentistry of New Jersey, Newark, NJ; †The International Center for AIDS Care and Treatment Programs, Mailman School of Public Health, and College of Physicians and Surgeons, Columbia University, New York, NY; ‡FHI, Durham, NC; §The School of Medicine; ∥The School of Nursing; and the ¶School of Public Health, University of North Carolina at Chapel Hill, Chapel Hill, NC; #Centers for Disease Control and Prevention, Atlanta, GA; **Division of AIDS, National Institutes of Health, Bethesda, MD; ††Rollins School of Public Health, Emory University, Atlanta, GA; and ‡‡Harlem Hospital, New York, NY.
This project was supported by the HIV Prevention Trials Network and sponsored by the National Institute of Allergy and Infectious Disease and the National Institute of Mental Health, both in Bethesda, MD, under award number U01 AIO68619. The authors' work on this article was supported in part by grants from National Institute of Allergy and Infectious Disease and the National Institute of Mental Health, under award numbers U01 AI069466-0351 (Dr S.L.H.), U01 AI069466 (Dr W.M.E. and Dr J.J.), AI06819 (Dr J.J.), U01 AIO68619 (Ms D.F.H.), and U01 AIO69423 (Dr A.A.A., Dr C.I.F., and Dr C.E.G.); and the Emory Center for AIDS Research, Atlanta, GA, under award number P30 AI050409 (Dr G.W.).
The views expressed herein are solely the responsibility of the authors and do not necessarily represent the official views of National Institute of Allergy and Infectious Disease, the National Institute of Mental Health, National Institutes of Health, the HIV Prevention Trials Network, the Centers for Disease Control and Prevention, or the funders of these organizations.
Correspondence to: Sally L. Hodder, MD, University of Medicine and Dentistry of New Jersey-New Jersey Medical School, 185 South Orange Avenue, MSB I-510, Newark, NJ 07101 (e-mail: firstname.lastname@example.org).
HIV incidence in the United States has remained an estimated 56,000 cases annually since 1991.1 The lack of substantive progress in reducing new HIV infections for almost 20 years is noteworthy despite remarkable advances,2 including the advent of rapid HIV testing, opt-out testing, and a variety of potent once-daily antiretroviral therapies and the availability of evidence-based behavioral interventions.3
Unlike the generalized epidemic in regions of sub-Saharan Africa, the US HIV epidemic is concentrated among certain subpopulations, particularly men who have sex with men (MSM) and persons of color.4 Although the high HIV prevalence among MSM in the United States is well recognized, the impact of HIV on women is less widely appreciated. Moreover, women at risk for HIV acquisition frequently do not appreciate this risk. The HIV epidemic among US women is, in many ways, hidden from effective dialogue, both among the populations at risk and within the broader scientific community. We summarize current epidemiology of HIV/AIDS among US women and discuss critical components that must be brought together in a cohesive plan to reduce new HIV infections in US women.
Epidemiology of HIV in US Women
Prevalence and incidence trends depict a concentrated epidemic with hot spots that vary by location, poverty rate, race/ethnicity, and transmission mode. By 2003, an estimated 1.1 million US adults and adolescents were HIV infected; approximately 21% of HIV-infected individuals are unaware of their infection.5,6 Although US HIV incidence estimates peaked at 150,000 cases per year during the mid-1980s, followed by a plateau at about 56,000 cases per year since 1991,1 the annual rate of new HIV cases has been increasing in certain subgroups, particularly MSM and black and Latina women. Eighty percent of HIV cases in women occur in black and Hispanic women, who together constitute just 25% of the US female population.7 Using back-calculation modeling, Rosenberg and Biggar8 reported that although HIV incidence was declining in white men aged 20-25 years, it was increasing in women in the same age group.
The HIV epidemic among US women is concentrated in the Northeast and South, with a significantly higher proportion of HIV infections occurring in areas with high poverty rates.9 Heterosexual activity has been the major mode of HIV acquisition for US women since 1995, when it surpassed injection drug use (IDU).10 Of women newly identified as HIV infected, 83% are estimated to have acquired HIV heterosexually, with most of the remaining acquiring HIV through IDU.7
Trends in AIDS rates among US women are of particular concern. Although women accounted for only 15% of AIDS cases from 1981 to 1995, they accounted for 27% of AIDS cases from 2001 to 2004.11 The Centers for Disease Control and Prevention reported a 15% increase in AIDS cases among women from 1999 to 2003, compared with a 1% increase in men.11 In addition, estimated AIDS diagnoses are 23 times greater in black women than in white women.12
Mortality trends among women with HIV are striking. Although the death rate due to HIV has decreased, HIV remains the third most common cause of death among black women aged 35-44 and the fourth most common cause of death among younger black women aged 25-34.12 The age-adjusted annual death rate due to HIV among black women during 2001-2005 was higher than that observed in every racial/ethnic group except non-Hispanic black males.13 Similarly, when compared with white women, black women with HIV have a 13-fold mortality risk ratio.14
Why Are Women at Risk for HIV?
Many factors contribute to HIV acquisition among women. Gender inequalities, both social and economic, hamper some women's abilities to negotiate condom use and other safer sex behaviors.15,16 Interpersonal violence is a risk factor for HIV among women, regardless of race or ethnicity.17 Factors associated with transmission of HIV and other sexually transmitted infections (STIs) include poverty, lack of access to medical care, poor knowledge about HIV/AIDS, lower social status,18,19 financial dependence on male partners, assortative mixing within HIV prevalence communities,20 feelings of invincibility, low self-esteem, and alcohol and drug use.21
However, individual risk behaviors do not explain the dramatic racial disparities in STI and HIV rates.22,23 In one study, black men and women with “low-risk” behaviors had 25-fold higher incidence of HIV and STIs compared with their white counterparts,23 a disparity that remains unexplained. Black women may underestimate the HIV risk status of their male partners; 6% of HIV-infected black women versus 14% of HIV-infected white women reported having a bisexual male partner, despite the fact that more than twice as many black HIV-infected men as white HIV-infected men (34% vs 13%) reported sex with both men and women.24 More black men and women than white are unaware of their HIV infection.25,26 These data may reflect a number of factors, including differences in HIV testing uptake, HIV prevalence, and structural features of the social environment. Sexual networks shaped not only by individual preferences and behaviors but also by macroeconomic, political, societal, and other structural features of the environment play a critical role in HIV acquisition among women.20,27,28 Concurrent sexual partnerships can amplify HIV transmission, particularly when one partner has early HIV infection, a period with high transmissibility.27,29 The higher prevalence of concurrent partnerships observed in US black and Hispanic men may contribute to racial disparities in HIV rates among US women.30 Sexual mixing patterns connecting women at low risk for HIV with men at higher risk may increase HIV acquisition in women; such mixing patterns have been observed among black men and women in the southeastern US.20
Recent studies demonstrate strong associations between prior incarceration9 or incarceration of a partner31 with HIV infection in US women. Though correctional inmates may view themselves at low or no risk for HIV acquisition,32 HIV prevalence among prisoners is more than 2.5 times higher than the general US population with a relatively high proportion of HIV-infected persons passing through the correctional system.33-35 The racial disparity of incarceration is striking: 1 in 9 black men between the ages of 20 and 34 is incarcerated, compared with 1 in 30 US men in the same age group.36 Incarceration influences sexual networks by disrupting stable sexual partnerships and has been associated with concurrent partnerships and dissortative mixing that promote HIV transmission.20,31,37 To date, incarceration has not been consistently used as an HIV prevention opportunity; condoms and clean injection equipment are unavailable to inmates in some correctional systems. Similarly, HIV testing policies vary widely among correctional systems.
HIV Prevention for US Women: Current Status
Early domestic HIV prevention successes included implementation of mandatory blood product screening and effective programs for prevention of mother-to-child transmission.2 Harm reduction programs throughout the United States have contributed to sharp declines in new HIV diagnoses among IDUs.38,39
Unfortunately, although consistent male condom use is known to be efficacious in reducing HIV transmission40 and female condoms have been assumed to be similar to male condoms in preventing HIV,41 condom implementation has not been effectively realized to decrease numbers of new HIV infections. Over the past decade, multiple microbicide trials have been disappointing.42-46 However, a number of ongoing trials are assessing new vaginal microbicides and antiretroviral drugs for pre-exposure prophylaxis,47,48 and results from the CAPRISA 004 microbicide study (a double-blind randomized placebo-control study among 989 women) recently demonstrated tenofovir 1% vaginal gel to have 40% efficacy in preventing HIV acquisition.49 To date, multiple vaccine trials have failed to prevent HIV transmission,50,51 with the possible exception of a recombinant canarypox vector vaccine (ALVAC-HV) plus 2 booster injections of recombinant gp120, which demonstrated vaccine efficacy of 31.2% (95% CI: 1.1 to 52.1; P = 0.04) in modified intent-to-treat analysis.52 Although statistically significant and perhaps useful to inform development of future vaccines, this 6-injection vaccine series did not demonstrate statistically significant efficacy in the per protocol analysis and had no effect on the level of HIV-1 viremia.
Antiretroviral treatment as a strategy to decrease HIV transmission has been the subject of recent interest.53-56 However, individuals with known HIV infection in the United States confront an array of barriers to health care access, medication adherence, and achievement of optimal virologic outcomes needed for this approach to effectively prevent HIV transmission.57
Multiple behavioral interventions to prevent HIV acquisition by women have been developed. However, a recent review of this area identified only 7 behavioral interventions demonstrating subsequent reductions in unprotected sexual intercourse3 and STIs,58,59 and none of the studies used HIV incidence as an end point. An additional limitation of most of these studies was a requirement that participating women attend multiple sessions, limiting the feasibility of broad implementation of these interventions in at-risk communities. Furthermore, few of the interventions attempted to directly influence social networks or sexual behaviors of women's partners-a critical component to HIV prevention in US women.60-62 Of 11 interventions listed as effective for women of color by the Centers for Disease Control and Prevention,63 none have assessed effect on HIV acquisition.
The Way Forward
Four areas must be urgently addressed to effectively decrease new HIV infections in US women. First, an absence of rigorous HIV incidence data among at-risk women impedes design of prevention trials with HIV incidence as primary end point; sample size calculations are not feasible without reliable estimates of incidence in the target population.
Second, behavioral strategies addressing male partners of women are needed. To date, only limited research has attempted to alter the sexual attitudes and behaviors of heterosexual and bisexual men.58,61,62 Research evaluating strategies that favorably influence gender norms and behaviors of men are critically needed. Although data suggest that sexual networks may be effectively used to identify cases of undiagnosed HIV,64 few sexual or social network interventions have been evaluated in women.65
Third, expanded HIV testing and linkage to care and effective antiretroviral treatment of individuals with HIV are critical to successful HIV prevention. Novel programs must be developed to facilitate effective virologic suppression among persons living in social chaos (ie, high poverty rates, high community violence, homelessness, and fragile social supports).
Finally, it is heartening that a national HIV/AIDS Strategy for the United States has recently been created.66 Moving forward, we must assure that HIV prevention plans continue to recommend implementation of proven strategies and promptly incorporate future HIV prevention trial results.
The ongoing HIV epidemic among US women, particularly black and Hispanic women, must receive the attention it is due. Research is needed to identify effective interventions that decrease US women's risk of HIV infection and are feasible to scale up in these populations. In addition, there is an urgent need to establish programs that enable US women to protect themselves. New, innovative prevention programing must build upon knowledge gained from past HIV prevention trials. Equally critical is the effective implementation of a multidimensional HIV prevention plan incorporating community, correctional institutions, and treatment programs (including support services such as substance abuse programs). Only by accelerating both research and programmatic efforts will the hidden epidemic of HIV among US women emerge into the light and be effectively addressed.
The authors wish to acknowledge the contributions of Drs. Sten Vermund, Quarraisha Abdool-Karim, David Metzger, Nirupama Sista and Ms. Harmony Waller. This project was supported by the HIV Prevention Trials Network (HPTN) and sponsored by the National Institute of Allergy and Infectious Diseases (NIAID) in Bethesda, MD, under award number U01 AI068619. The authors' work on this manuscript was supported in part by grants from NIAID and NIMH, under award numbers U01 AI069466 (Dr Hodder), U01 AI069466 (Dr El-Sadr and Dr Justman), AI06819 (Dr Justman), U01 AI068619 (Ms Haley), and U01 AI069423 (Dr Adimora, Dr Fogel, and Dr Golin); and the Emory Center for AIDS Research, Atlanta, GA, under award number P30 AI050409 (Dr Wingood). The views expressed herein are solely the responsibility of the authors and do not necessarily represent the official views of NIAID, NIH, the HPTN, the Centers for Disease Control and Prevention, or its funders.
1. Hall HI, Song R, Rhodes P, et al. Estimation of HIV incidence in the United States. JAMA
. 2008;300:520-529. doi:10.1001/jama.300.5.520.
3. Lyles CM, Kay LS, Crepaz N, et al. Best-evidence interventions: findings from a systematic review of HIV behavioral interventions for US populations at high risk, 2000-2004. Am J Public Health
. 2007;97:133-143. doi: 10.2105/AJPH.2005.076182.
4. El-Sadr WM, Mayer KH, Hodder SL. AIDS in America-forgotten but not gone. N Engl J Med
5. Campsmith M, Rhodes PH, Hall HI, et al. Undiagnosed HIV prevalence among adults and adolescents in the United States at the end of 2006. J Acquir Immune Defic Syndr
8. Rosenberg PS, Biggar RJ. Trends in HIV incidence among young adults in the United States. JAMA
9. Adimora AA, Schoenbach VJ, Doherty IA. HIV and African Americans in the southern United States: sexual networks and social context. Sex Transm Dis
. 2006;33(Suppl 7):S39-S45.
10. Centers for Disease Control and Prevention. 1996 Sexually Transmitted Disease Surveillance Report
. Atlanta, GA: Centers for Disease Control and Prevention. Available at: http://wonder.cdc.gov/wonder/STD/Title4000.html
. Accessed August 10, 2010.
11. Centers for Disease Control and Prevention. Epidemiology of HIV/AIDS-United States, 1981-2005
. MMWR Morb Mortal Wkly Rep
14. Levine RS, Briggs NC, Kilbourne BS, et al. Black-white mortality from HIV in the United States before and after introduction of highly active antiretroviral therapy in 1996. Am J Public Health
. 2007;97:1884-1892. doi: 10.2105/AJPH.2005.081489.
15. El-Bassel N, Caldeira N, Ruglass L, et al. Addressing the unique needs of African American women in HIV prevention. Am J Public Health
. 2009;99:996-1001. doi: 10.2105/AJPH.2008.140541.
16. Wingood GM, DiClemente RJ. Partner influences and gender-related factors associated with noncondom use among young adult African American women. Am J Community Psychol
17. Wyatt GE, Myers HF, Williams JK, et al. Does a history of trauma contribute to HIV risk for women of color? Implications for prevention and policy. Am J Public Health
18. Fleming PL, Lansky A, Lee LM, et al. The epidemiology of HIV/AIDS in women in the southern United States. Sex Transm Dis
. 2006;33(Suppl 7):S32-S38.
19. Thomas JC, Schoenbach VJ, Weiner DH, et al. Rural gonorrhea in the southeastern United States: a neglected epidemic? Am J Epidemiol
20. Doherty IA, Schoenbach VJ, Admiora AA. Sexual mixing patterns and heterosexual HIV transmission among African Americans in the southeastern United States. J Acquir Immune Defic Syndr
21. Forna FM, Fitzpatrick L, Adimora AA, et al. A case-control study of factors associated with HIV infection among black women. J Natl Med Assoc
22. Harawa NT, Greenland S, Cochran SD, et al. Do differences in relationship and partner attributes explain disparities in sexually transmitted disease among young white and black women? J Adolesc Health
. 2003;32:187-191. doi: 10.1016/S1054-139X(02)00458-5.
23. Hallfors DD, Iritani BJ, Miller WC, et al. Sexual and drug behavior patterns and HIV and STD racial disparities: the need for new directions. Am J Public Health
24. Montgomery JP, Mokotoff ED, Gentry AC, et al. The extent of bisexual behaviour in HIV-infected men and implications for transmission to their female sex partners [erratum in AIDS Care
. 2004;16:923]. AIDS Care
25. Centers for Disease Control and Prevention. HIV prevalence, unrecognized infection, and HIV testing among men who have sex with men-five U.S. cities, June 2004-April 2005. MMWR Morb Mortal Wkly Rep
. 2005;54:597-601. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5424a2.htm
. Accessed August 10, 2010.
27. Morris M, Kretzschmar M. Concurrent partnerships and the spread of HIV. AIDS
28. Adimora AA, Schoenbach VJ. Contextual factors and the black-white disparity in heterosexual HIV transmission. Epidemiology
29. Adimora AA, Schoenbach VJ, Martinson FE, et al. Concurrent partnerships among rural African Americans with recently reported heterosexually transmitted HIV infection. J Acquir Immune Defic Syndr
30. Adimora AA, Schoenbach VJ, Doherty IA. Concurrent sexual partnerships among men in the United States. Am J Public Health
31. Adimora AA, Schoenback VK. Social context, sexual networks, and racial disparities in rates of sexually transmitted infections. J Infect Dis
. 2005;191(Suppl 1):S115-S122.
32. Conklin TJ, Lincoln T, Tuthill RW. Self-reported health and prior health behaviors of newly admitted correctional inmates. Am J Public Health
33. Hammett TM, Gaiter JL, Crawford C. Reaching seriously at-risk populations: health interventions in criminal justice settings. Health Educ Behav
34. Hammett TM, Harmon MP, Rhodes W. The burden of infectious disease among inmates and releases from correctional facilities, 1997. Am J Public Health
. 2002;92:1789-1794. Available at: http://www.ojp.usdoj.gov/bjs/pub/pdf/hivp06.pdf
. Accessed August 10, 2010.
35. Maruschak LM, Beavers R. HIV in Prisons, 2007-2008 [NCJ 228307]
. Washington, DC: Bureau of Justice Statistics Bulletin, Office of Justice Programs, US Department of Justice; December 2009. Available at: http://bjs.ojp.usdoj.gov/index.
cfm?ty=pbdetail&iid=1747. Accessed August 16, 2010.
37. Khan MR, Doherty IA, Schoenbach VJ, et al. Incarceration and high-risk sex partnerships among men in the United States. J Urban Health
38. Board on Global Health, Institute of Medicine of the National Academies. Preventing HIV Infection Among Injecting Drug Users in High Risk Countries: An Assessment of the Evidence
. Washington, DC: National Academies Press; 2007.
39. Dodd RY, Notari EP IV, Stramer SL. Current prevalence and incidence of infectious disease markers and estimated window-period risk in the American Red Cross blood donor population. Transfusion
40. Weller SC, Davis-Beaty K. Condom effectiveness in reducing heterosexual HIV transmission. Cochrane Database Syst Rev
. 2002;1;CD003255. doi: 10.1002/14651858.CD003255.
41. French PP, Latka M, Gollub EL, et al. Use-effectiveness of the female versus male condom in preventing sexually transmitted disease in women. Sex Transm Dis
42. Chisembele M, Crook A, Gafos M, et al.PRO2000 vaginal gel is ineffective in preventing HIV infection: results of the MDP301 Phase III microbicide trial [oral abstract; paper #87LB]. Presented at: 17th Conference on Retroviruses and Opportunistic Infections (CROI); February 16-19, 2010; San Francisco, CA. Available at: http://www.retroconference.org/2010/Abstracts/39763.htm
. Accessed August 10, 2010.
43. Van Damme L, Ramjee G, Alary M, et al. Effectiveness of COL-1492, a nonoxynol-9 vaginal gel, on HIV-1 transmission in female sex workers: a randomised controlled trial [erratum: Lancet
. 2002;360:1892]. Lancet
. 2002;360:971-977. doi:10.1016/S0140-6736(02)11079-8.
44. Feldblum PJ, Adeiga A, Bakare R, et al. SAVVY vaginal gel (C31G) for prevention of HIV infection: a randomized controlled trial in Nigeria. PLoS ONE
. 2008;3:e1474. doi:10.1371/journal.pone.0001474.
45. Van Damme L, Govinden R, Mirembe FM, et al. Lack of effectiveness of cellulose sulfate gel for the prevention of vaginal HIV transmission. N Engl J Med
46. Skoler-Karpoff S, Ramjee G, Ahmed K, et al. Efficacy of Carraguard for prevention of HIV infection in women in South Africa: a randomised, double-blind, placebo-controlled trial. Lancet
. 2008;372:1977-1987. doi:10.1016/S0140-6736(08)61842-5.
47. Okwundu CI, Okoromah CA. Antiretroviral pre-exposure prophylaxis (PrEP) for preventing HIV in high-risk individuals. Cochrane Database Syst Rev
. 2009;1:CD007189. doi: 10.1002/14651858.CD007189.pub2.
48. Young T, Arens FJ, Kennedy GE, et al. Antiretroviral post-exposure prophylaxis (PEP) for occupational HIV exposure. Cochrane Database Syst Rev
. 2007;1:CD002835. doi: 10.1002/14651858.CD002835.pub3.
49. Abdool-Karim Q, Abdool Karim SS, Frohlich JA, et al. Effectiveness and safety of tenofovir gel, an antiretroviral microbicide, for the prevention of HIV infection in women. Science
. doi: 10.1126/science.1193748. Published online July 19, 2010.
50. Flynn NM, Forthal DN, Harro CD, et al. Placebo-controlled phase 3 trial of a recombinant glycoprotein 120 vaccine to prevent HIV-1 infection. J Infect Dis
51. Buchbinder SP, Mehrotra DV, Duerr A, et al. Efficacy assessment of a cell-mediated immunity HIV-1 vaccine (the Step Study): a double-blind, randomised, placebo-controlled test-of-concept trial. Lancet
. 2008;372:1881-1893. doi:10.1016/S0140-6736(08)61591-3.
52. Rerks-Ngarm S, Pitisuttihum P, Nitayaphan S, et al. Vaccination with ALVAC and AIDSVAX to prevent HIV-1 infection in Thailand. N Engl J Med
53. Dodd PJ, Garnett GP, Hallett TB. Examining the promise of HIV elimination by ‘test and treat’ in hyperendemic settings. AIDS
. 2010;24:729-735. doi: 10.1097/QAD.0b013e32833433fe.
54. Granich RM, Gilks CF, Dye C, et al. Universal voluntary HIV testing with immediate antiretroviral therapy as a strategy for elimination of HIV transmission: a mathematical model. Lancet
. 2009;373:48-57. doi:10.1016/S0140-6736(08)61697-9.
55. Wagner BG, Blower S. Voluntary universal testing and treatment is unlikely to lead to HIV elimination: a modeling analysis. Nature Precedings
. Posted October 29, 2009. hdl:10101/npre.2009.3917.1.
56. Dieffenbach CW, Fauci AS. Universal voluntary testing and treatment for prevention of HIV transmission. JAMA
57. Committee on the Public Financing and Delivery of HIV Care, Board on Health Promotion and Disease Prevention, Institute of Medicine of the National Academies. Public Financing and Delivery of HIV/AIDS Care: Securing the Legacy of Ryan White
. Washington, DC: National Academy Press; 2005. Available at: http://books.nap.edu/openbook.
php?record_id=10995&page=R1#. Accessed August 10, 2010.
58. Shain RN, Piper JM, Newton ER, et al. A randomized, controlled trial of a behavioral intervention to prevent sexually transmitted disease among minority women. N Engl J Med
59. Jemmott LS, Jemmott JB, O'Leary A. Effects on sexual risk behavior and STD rate of brief HIV/STD prevention interventions for African American women in primary care settings. Am J Public Health
. 2007;97:1034-1040. doi: 10.2105/AJPH.2003.020271.
60. Crepaz N, Marhsall KJ, Aupont LW, et al. The efficacy of HIV/STI behavioral interventions for African American females in the United States: a meta-analysis. Am J Public Health
. 2009;99:2069-2078. doi: 10.2105/AJPH.2008.139519.
61. Kamb ML, Fishbein M, Douglas JM, et al. Efficacy of risk-reduction counseling to prevent human immunodeficiency virus and sexually transmitted diseases: a randomized controlled trial. Project RESPECT Study Group. JAMA
. 1998;280:1161-1167. doi:10.1001/jama.280.13.1161.
62. National Institute of Mental Health (NIMH) Multisite HIV Prevention Trial Group. The NIMH Multisite HIV Prevention Trial: reducing HIV sexual risk behavior. Science
. 1998;280:1889-1894. doi: 10.1126/science.280.5371. 1889.
64. Centers for Disease Control and Prevention. Use of social networks to identify persons with undiagnosed HIV infection-seven U.S. cities, October 2003-September 2004. MMWR Morb Mortal Wkly Rep
. 2005;54:601-605. Available at: http://www.cdc.gov/mmwr/preview/mmwrhtml/mm5424a3.htm
. Accessed August 10, 2010.
65. Weeks MR, Clair S, Borgatti SP, et al. Social networks of drug users in high-risk sites: finding the connections. AIDS Behav
. 2002;6(2):193-206. doi: 10.1023/A:1015457400897.