Anogenital warts guide: Etiology and epidemiology
This guide focuses on the assessment and management of external anogenital warts (AGW) caused by human papillomaviruses (HPV). HPV vaccination and HPV-related cancer screening recommendations are beyond the scope of this guide.
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Etiology
Anogenital warts (AGW) are caused by human papillomaviruses (HPV)Footnote 1Footnote 2Footnote 3Footnote 4Footnote 5Footnote 6Footnote 7Footnote 8Footnote 9Footnote 10. HPV are small, double-stranded DNA viruses that infect the epitheliumFootnote 6Footnote 11Footnote 12. Approximately 40 types of HPV are known to affect the human anogenital areaFootnote 3Footnote 6Footnote 7Footnote 8Footnote 9Footnote 14Footnote 15Footnote 10. More than 90% of AGW are caused by HPV types 6 and 11Footnote 3Footnote 4Footnote 5Footnote 6Footnote 7Footnote 8Footnote 10Footnote 11Footnote 12Footnote 13Footnote 14Footnote 16. HPV types 6 and 11 are categorized as low-risk of oncogenesis based on their infrequent association with anogenital cancersFootnote 6Footnote 7Footnote 8Footnote 9Footnote 10Footnote 11Footnote 15Footnote 16.
Epidemiology
AGW caused by HPV are commonFootnote 1Footnote 2Footnote 4Footnote 7Footnote 10Footnote 11Footnote 14Footnote 15. AGW are associated with significant healthcare utilization costs and adverse psychosexual effectsFootnote 1Footnote 4Footnote 7Footnote 8Footnote 9Footnote 11Footnote 14Footnote 17.
Co-infection with multiple types of HPV is commonFootnote 1Footnote 2Footnote 7Footnote 9Footnote 10Footnote 13Footnote 18Footnote 19Footnote 20.
Infection with one type of HPV does not appear to be protective against acquisition of other typesFootnote 18Footnote 19Footnote 20.
HPV vaccine trials and population studies documented the incidence and prevalence of AGW prior to the establishment of HPV vaccination programs.
Globally:
- Between December 2001 and May 2003, AGW developed in 3.5% of 15- to 24-year-old femalesFootnote a from 16 countries who were part of the placebo group in an HPV vaccine trial. This corresponds with an incidence rate of 870 per 100,000 person years (PY) at riskFootnote 21.
- In a survey conducted between November 2004 and June 2005, 10.6% of femalesFootnote a aged 18 to 45 from Denmark, Iceland, Norway and Sweden reported having ever been diagnosed with AGWs. 1.6% of those surveyed reported experiencing genital warts within the prior 12 monthsFootnote 22.
- In the 1999 - 2004 National Health and Nutrition Examination Survey, 5.6% of sexually active Americans aged 18 to 59 years reported ever having been diagnosed with AGWFootnote 23.
- In the United States, the incidence of AGW among people with private insurance in 2001 was 205 per 100,000 person-years at riskFootnote 24.
In Canada:
- Studies in Manitoba in 2004Footnote 25 and in British Columbia (B.C.) in 2006Footnote 26 found incidence rates of AGW of 154 and 131 per 100,000 malesFootnote a and 120 and 121 per 100,000 femalesFootnote a, respectively.
- AGW incidence in both studies was highest for malesFootnote a aged 25-to-29 years, and femalesFootnote a aged 20 to 24 yearsFootnote 25Footnote 26.
- These studies reported prevalence rates of AGW of 157 and 165 per 100,000 malesFootnote a and 128 and 140 per 100,000 femalesFootnote a in Manitoba and B.C., respectivelyFootnote 26Footnote 27 From 1998 to 2006, incidence and prevalence of AGW in B.C. increasedFootnote 26.
In recent years, AGW occurrence has decreased markedly in countries where HPV vaccination programs have been introducedFootnote 4Footnote 8Footnote 14Footnote 28Footnote 29:
- A systematic review found that, 5 to 8 years after vaccination in high-income countries, diagnoses of AGW decreased by 67% among girlsFootnote b aged 15 to 19 years, by 54% among womenFootnote b aged 20 to 24 years, and by 31% among womenFootnote b aged 25 to 29 years. In parallel, diagnoses of AGW decreased by 48% among boysFootnote b 15 to 19 years, and by 32% among menFootnote b aged 20 to 24 yearsFootnote 28.
- These findings have been affirmed in the Canadian context. A systematic review of studies published between September 1, 2006 and September 1, 2016 found that the incidence of AGW decreased by up to 45% in cohorts eligible for publicly funded quadrivalent HPV vaccinesFootnote 8. A subsequent Manitoba study documented a decline in incident AGW of 72% among 16- to 18-year-old femalesFootnote a and 51% among malesFootnote a after the introduction of a publicly-funded, school-based quadrivalent HPV vaccination program for femalesFootnote a in 2008Footnote 29.
Footnotes
- Footnote a
-
Published research summarized above does not systematically define or distinguish between sex and gender, and frequently refers to sex and gender as binary concepts. Where sex was the apparent variable measured by investigators, the terms "male" and "female" have been used to summarize the results.
- Footnote b
-
The terminology used by the authors has been used to report the findings of the systematic review by Drolet et alFootnote 28.
References
References:
- Footnote 1
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Aubin F, Prétet J-L, Jacquard A-C, Saunier M, Carcopino X, Jaroud F, et al. Human papillomavirus genotype distribution in external acuminata condylomata: A large French national study (EDiTH IV). Clin Infect Dis 2008;47(5):610-615.
- Footnote 2
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Ball SL, Winder DM, Vaughan K, Hanna N, Levy J, Sterling JC, et al. Analyses of human papillomavirus genotypes and viral loads in anogenital warts. J Med Virol 2011;83(8):1345-1350.
- Footnote 3
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Forcier M, Musacchio N. An overview of human papillomavirus infection for the dermatologist: Disease, diagnosis, management, and prevention. Dermatol Ther 2010;23(5):458-476.
- Footnote 4
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Karnes JB, Usatine RP. Management of external genital warts. Am Fam Phys 2014;90(5):312-318.
- Footnote 5
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O'Mahony C, Gomberg M, Skerlev M, Alraddadi A, de las Heras-Alonso ME, Majewski S, et al. Position statement for the diagnosis and management of anogenital warts. J Eur Acad Dermatol Venereol 2019;33(6):1006-1019.
- Footnote 6
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Public Health Agency of Canada. Human papillomavirus (HPV) vaccines: Canadian Immunization Guide For health professionals. 2017. Available at: https://www.canada.ca/en/public-health/services/publications/healthy-living/canadian-immunization-guide-part-4-active-vaccines/page-9-human-papillomavirus-vaccine.html.
- Footnote 7
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Steben M, Garland SM. Genital warts. Best Pract Res Clin Obstet Gynaecol 2014;28(7):1063-1073.
- Footnote 8
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Steben M, Tan Thompson M, Rodier C, Mallette N, Racovitan V, DeAngelis F, et al. A Review of the Impact and Effectiveness of the Quadrivalent Human Papillomavirus Vaccine: 10 Years of Clinical Experience in Canada. J Obstet Gynaecol Can 2018;40(12):1635-1645.
- Footnote 9
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Trottier H, Franco EL. The epidemiology of genital human papillomavirus infection. Vaccine 2006;24(SUPPL. 1):S4.
- Footnote 10
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Yanofsky VR, Patel RV, Goldenberg G. Genital warts: A comprehensive review. J Clin Aesthetic Dermatol 2012;5(6):25-36.
- Footnote 11
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Chelimo C, Wouldes TA, Cameron LD, Elwood JM. Risk factors for and prevention of human papillomaviruses (HPV), genital warts and cervical cancer. J Infect 2013;66(3):207-217.
- Footnote 12
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International Agency for Research on Cancer Working Group. Human papillomaviruses (HPV). IARC Monographs 2007;90.
- Footnote 13
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Chan PKS, Luk ACS, Luk TNM, Lee K-F, Cheung JLK, Ho K-M, et al. Distribution of human papillomavirus types in anogenital warts of men. J Clin Virol 2009;44(2):111-114.
- Footnote 14
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Tyros G, Mastraftsi S, Gregoriou S, Nicolaidou E. Incidence of anogenital warts: epidemiological risk factors and real-life impact of human papillomavirus vaccination. Int J STD AIDS 2021;32(1):4-13.
- Footnote 15
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Workowski KA, Bachmann LH, Chan PA, Johnston CM, Muzny CA, Park I, et al. Sexually Transmitted Infections Treatment Guidelines, 2021. MMWR Recomm Rep 2021 07 23;70(4):1-187.
- Footnote 16
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Brianti P, De Flammineis E, Mercuri SR. Review of HPV-related diseases and cancers. The new microbiologica 2017;40(2):80-85.
- Footnote 17
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Dawar DM, Harris MT, McNeil DS. Update on Human Papillomavirus (HPV) Vaccines: An Advisory Committee Statement (ACS) National Advisory Committee on Immunization (NACI). Can Commun Dis Rep 2012 Jan 02;38(ACS-1):1-62.
- Footnote 18
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Liaw K-L, Hildesheim A, Burk RD, Gravitt P, Wacholder S, Manos MM, et al. A prospective study of human papillomavirus (HPV) type 16 DNA detection by polymerase chain reaction and its association with acquisition and persistence of other HPV types. J Infect Dis 2001;183(1):8-15.
- Footnote 19
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Rousseau M-C, Pereira JS, Prado JCM, Villa LL, Rohan TE, Franco EL. Cervical coinfection with human papillomavirus (HPV) types as a predictor of acquisition and persistence of HPV infection. J Infect Dis 2001;184(12):1508-1517.
- Footnote 20
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Thomas KK, Hughes JP, Kuypers JM, Kiviat NB, Lee S-, Adam DE, et al. Concurrent and sequential acquisition of different genital human papillomavirus types. J Infect Dis 2000;182(4):1097-1102.
- Footnote 21
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Garland SM, Steben M, Sings HL, James M, Lu S, Railkar R, et al. Natural history of genital warts: Analysis of the placebo arm of 2 randomized phase III trials of a quadrivalent human papillomavirus (types 6, 11, 16, and 18) Vaccine. J Infect Dis 2009;199(6):805-814.
- Footnote 22
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Kjær SK, Tran TN, Sparen P, Tryggvadottir L, Munk C, Dasbach E, et al. The burden of genital warts: A study of nearly 70,000 women from the general female population in the 4 Nordic countries. J Infect Dis 2007;196(10):1447-1454.
- Footnote 23
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Dinh T-H, Sternberg M, Dunne EF, Markowitz LE. Genital warts among 18- to 59-year-olds in the United States, National Health and Nutrition Examination Survey, 1999-2004. Sex Transm Dis 2008;35(4):357-360.
- Footnote 24
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Koshiol JE, St. Laurent SA, Pimenta JM. Rate and predictors of new genital warts claims and genital warts-related healthcare utilization among privately insured patients in the United States. Sex Transm Dis 2004;31(12):748-752.
- Footnote 25
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Kliewer EV, Demers AA, Elliott L, Lotocki R, Butler JR, Brisson M. Twenty-year trends in the incidence and prevalence of diagnosed anogenital warts in Canada. Sex Transm Dis 2009;36(6):380-386.
- Footnote 26
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Marra F, Ogilvie G, Colley L, Kliewer E, Marra CA. Epidemiology and costs associated with genital warts in Canada. Sex Transm Infect 2009;85(2):111-115.
- Footnote 27
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Kliewer EV, Demers AA, Elliott L, Lotocki R, Butler JRG, Brisson M. Twenty-year trends in the incidence and prevalence of diagnosed anogenital warts in canada. Sex Transm Dis 2009;36(6):380-386.
- Footnote 28
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Drolet M, Bénard É, Pérez N, Brisson M, Ali H, Boily M-C, et al. Population-level impact and herd effects following the introduction of human papillomavirus vaccination programmes: updated systematic review and meta-analysis. Lancet 2019;394(10197):497-509.
- Footnote 29
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Righolt CH, Willows K, Kliewer EV, Mahmud SM. Incidence of anogenital warts after the introduction of the quadrivalent HPV vaccine program in Manitoba, Canada. PLoS ONE 2022;17(4):e0267646.
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