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State-Specific Rates of Primary and Secondary Syphilis Among Men Who Have Sex with Men — United States, 2015



Alex de Voux, PhD1,2; Sarah Kidd, MD2; Jeremy A. Grey, PhD3; Eli S. Rosenberg, PhD3; Thomas L. Gift, PhD2; Hillard Weinstock, MD2; Kyle T. Bernstein, PhD2 (View author affiliations)

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Summary

What is already known about this topic?

Syphilis rates in the United States have been steadily increasing since 2001, and gay, bisexual, and other men who have sex with men (collectively referred to as MSM) represent a disproportionate number of cases. In the absence of reliable, state-specific denominators it has been difficult to estimate state-specific rates and rate ratios to accurately measure the geographic variation and disparity.

What is added by this report?

State-specific rate ratios comparing the rate of syphilis among MSM with the rate among men reporting sex with women only ranged from 39.2 (Minnesota) to 342.1 (Hawaii); overall, MSM had a rate of primary and secondary syphilis 106.0 times the rate among men who reported sex with women only.

What are the implications for public health practice?

These state-specific rates further highlight the disproportionate impact of syphilis among MSM. Providers should screen sexually active MSM for syphilis at least annually and provide timely treatment according to national sexually transmitted diseases treatment guidelines.


In 2015, the rate of reported primary and secondary syphilis in the United States was 7.5 cases per 100,000 population, nearly four times the previous lowest documented rate of 2.1 in 2000 (1). In 2015, 81.7% of male primary and secondary syphilis cases with information on the sex of the sex partner were among gay, bisexual, and other men who have sex with men (collectively referred to as MSM) (1). These data suggest a disproportionate incidence of disease among MSM. However, attempts to quantify this disparity have been hindered by limited data on the size of the MSM population at the state level. To produce the first estimates of state-specific rates of primary and secondary syphilis among MSM, CDC used MSM population estimates based on a new methodology (2) and primary and secondary syphilis case counts reported in 2015 to the National Notifiable Diseases Surveillance System. Among 44 states reporting information on the sex of sex partners for ≥70% of male cases, the overall rate of primary and secondary syphilis among all men (aged ≥18 years) in the United States in 2015 was 17.5 per 100,000, compared with 309.0 among MSM and 2.9 among men who reported sex with women only. The overall rate of primary and secondary syphilis among MSM was 106.0 times the rate among men who have sex with women only and 167.5 times the rate among women.* These data highlight the disproportionate impact of syphilis among MSM and underscore the need for innovative and targeted syphilis prevention measures at the state and local level, especially among MSM. It is important that health care providers recognize the signs and symptoms of syphilis, screen sexually active MSM for syphilis at least annually, and provide timely treatment according to national sexually transmitted diseases treatment guidelines (3).

Case reports of primary and secondary syphilis cases for MSM, men who have sex with women only, and women were obtained from national data reported regularly by all states for 2015. These data include limited demographic and clinical information, including the sex of sex partners. Population estimates of the number of MSM by state were obtained using new methodology that makes use of census and population-based survey data (2). To estimate the MSM population size, the estimated percentage of MSM among men was adjusted (4) according to each U.S. county’s percentage of households with a male head and a male partner, obtained from American Community Survey summary data and urban-rural classification (large central metropolitan, large fringe metropolitan, medium or small metropolitan, or nonmetropolitan or rural) from the National Center for Health Statistics (4). The county’s percentage of MSM was adjusted according to the ratio of its percentage of male same-sex households to the overall percentage among all counties at the same urban-rural classification, which was then multiplied by the number of men in the county to achieve the estimated MSM population size. This final number was then scaled to equal 3.9% of the adult male population, based on a prior national MSM estimate (5).

To optimize stability of the estimates, the analysis was limited to the 44 states that included sex of sex partner in ≥70% of male primary and secondary syphilis case reports for 2015. The 70% threshold represented the best balance between including male cases of primary and secondary syphilis while gathering the most complete epidemiologic data for those cases. State-specific rates of primary and secondary syphilis among MSM were compared with rates of primary and secondary syphilis among men who have sex with women only and also among women (cases in men with unknown sex of sex partner were excluded from this analysis). Rate ratios were calculated as 1) the rate of primary and secondary syphilis among MSM divided by the rate among men who have sex with women only and 2) the rate among MSM divided by the rate among women.

Primary and secondary syphilis cases in the 44 states included in the analysis accounted for 83.4% of all 23,872 reported primary and secondary syphilis cases in the United States in 2015. Among the reported primary and secondary syphilis cases among men and women in these 44 states in 2015, 12,118 (60.8%) were among MSM, including 10,942 (54.9%) among men who had sex with men only and 1,176 (5.9%) cases among men who had sex with both men and women.

Among the 44 states, the overall rates of primary and secondary syphilis in 2015 among all men, MSM, men who have sex with women only, and women were 17.5, 309.0, 2.9, and 1.8 cases per 100,000 population, respectively. State-specific rates among MSM ranged from 73.1 per 100,000 population (Alaska) to 748.3 (North Carolina) (Table 1). The overall U.S. rate of primary and secondary syphilis among MSM was 106.0 times the rate among men who have sex with women only, with state-specific rate ratios ranging from 39.2 (Minnesota) to 342.1 (Hawaii). The overall rate of primary and secondary syphilis among MSM was 167.5 times the rate among women, with state-specific rate ratios ranging from 63.7 (Louisiana) to 2,140.3 (Hawaii).

Rates of primary and secondary syphilis among MSM varied by U.S. Census region and by state, with the highest rates in the South and West. Four of the five states with the highest primary and secondary syphilis rates among MSM were southern states (Louisiana, Mississippi, North Carolina, and South Carolina) (Table 2). Among states with the 10 highest rates of primary and secondary syphilis in the United States in 2015 (1), five states (Arizona, Louisiana, Mississippi, Nevada, and North Carolina) also ranked among the top 10 states with the highest rates of primary and secondary syphilis among MSM (Table 2).

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Discussion

These are the first state-specific rates of primary and secondary syphilis reported for MSM in the United States. The lowest state-specific MSM primary and secondary syphilis rate (73.1 in Alaska) exceeded the highest overall U.S. primary and secondary syphilis rate (70.9), which was observed in 1946. In every state, the incidence of reported syphilis among MSM was higher than the incidence among men who have sex with women only, with rate ratios ranging from 39.2 to 342.1. These data support CDC’s earlier findings using national population size estimates, which highlighted national disparities in syphilis incidence. In the earlier findings, the rate of syphilis incidence among MSM was estimated to be 154 per 100,000 population, compared with 2.2 per 100,000 among other men, resulting in a rate ratio of 71 (5), in comparison to the estimate of 106.0 in the current analysis. However, the previous findings were limited in their applicability to state or local areas because the percentage of adult males who are MSM varies widely among states.

Although state-specific incidence rates varied, even in low incidence states (e.g., North Dakota), syphilis rates among MSM were higher than those among men who have sex with women only. The geographic variation highlights the importance of these data for state and local health departments, which can use these data to better understand their local syphilis epidemiology and target resources and interventions to address disparities between MSM and other population groups. The comparison of state-specific rates also highlights the high disease incidence in the South. Four of the five states with the highest primary and secondary syphilis incidence rates among MSM in 2015 were southern states. The estimates of state-specific rates among men who have sex with women only, although lower than those among MSM, also have implications for the rates of syphilis among women. Trends in congenital syphilis tend to follow trends in the incidence of primary and secondary syphilis among women of reproductive age, which has been increasing recently (6). Congenital syphilis can result in serious health consequences in infants (6). Although CDC is limited by its data usage agreement with the Council of State and Territorial Epidemiologists to conduct data analysis at the state level (7), further analyses at the county level by state and local health jurisdictions could be helpful to inform public health action by elucidating geographic disparities in greater detail.

The findings in this report are subject to at least four limitations. First, analyses were restricted to states where the sex of sex partners (male, female, or both) was reported for ≥70% of male cases of primary and secondary syphilis cases during 2015. Although 83.4% of all reported primary and secondary syphilis reported in the United States during 2015 were included, these jurisdictions might not be representative of all persons who receive a diagnosis of primary and secondary syphilis. Second, the denominators used in calculating the rates of primary and secondary syphilis were estimates of the number of MSM in each state, based on the reporting of same-sex households in the American Community Survey; underreporting of same-sex households could result in an underestimation of the MSM population and an overestimation of primary and secondary syphilis rates. Third, cases of syphilis in men for whom the sex of sex partners was unknown were excluded in calculations for both MSM and men who have sex with women only. If MSM are more likely to underreport the sex of their sex partner, this might result in an underestimation of the rate of syphilis among MSM and consequent rate ratio when comparing syphilis rates among MSM and men who have sex with women only. Improving the quality of case report data regarding sex of sex partner information could increase the awareness of public health officials regarding the characteristics of syphilis within their communities. Finally, primary and secondary syphilis case report data likely underestimate the actual number of incident syphilis infections in the United States because not all infections are diagnosed and reported (8).

Despite these limitations, these findings are consistent with previous reports that showed pronounced disparities in primary and secondary syphilis rates between MSM and men who have sex with women only (5), and the use of state-specific MSM population sizes and primary and secondary syphilis case counts permits comparison of primary and secondary syphilis rates by state. Rates among MSM compared with men who have sex with women only were higher in every state, but state-specific data suggested that certain states might have a greater need for syphilis prevention. Because MSM represent the majority of all primary and secondary syphilis cases, the success of syphilis prevention programs is contingent upon addressing the high rates of syphilis among MSM. It is important that both private and public health care providers 1) recognize the signs and symptoms of syphilis, 2) conduct a comprehensive sexual history, 3) screen all sexually active MSM for syphilis at least annually, and 4) provide timely treatment according to national sexually transmitted diseases treatment guidelines (3). Part of this sexual history includes eliciting information on sexual practices and the sex of patients’ sex partners.§

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1Epidemic Intelligence Service, CDC; 2Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention, CDC; 3Department of Epidemiology, Rollins School of Public Health, Emory University, Atlanta, Georgia.

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* In this report “women” is used to describe both females aged ≥18 years (used for calculating rates for women) and females of unknown ages (used for calculating rates for men who had sex with women only).

Rate ratios were rounded to tenths.

§ https://www.cdc.gov/STD/treatment/SexualHistory.pdf.

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References

  1. CDC. Sexually transmitted disease surveillance 2015. Atlanta, GA: US Department of Health and Human Services, CDC; 2016. https://www.cdc.gov/std/stats15/std-surveillance-2015-print.pdf
  2. Grey JA, Bernstein KT, Sullivan PS, et al. Estimating the population sizes of men who have sex with men in US states and counties using data from the American Community Survey. JMIR Public Health Surveill 2016;2:e14. CrossRef PubMed
  3. Workowski KA, Bolan GA. Sexually transmitted diseases treatment guidelines, 2015. MMWR Recomm Rep 2015;64(No. RR-3). PubMed
  4. Oster AM, Sternberg M, Lansky A, Broz D, Wejnert C, Paz-Bailey G. Population size estimates for men who have sex with men and persons who inject drugs. J Urban Health 2015;92:733–43. CrossRef PubMed
  5. Purcell DW, Johnson CH, Lansky A, et al. Estimating the population size of men who have sex with men in the United States to obtain HIV and syphilis rates. Open AIDS J 2012;6(Suppl 1):98–107. CrossRef PubMed
  6. Bowen V, Su J, Torrone E, Kidd S, Weinstock H. Increase in incidence of congenital syphilis—United States, 2012–2014. MMWR Morb Mortal Wkly Rep 2015;64:1241–5. CrossRef PubMed
  7. CDC; Council of State and Territorial Epidemiologists. Data release guidelines for the National STD Morbidity Surveillance System. Atlanta, GA: US Department of Health and Human Services, CDC; 2005.
  8. Satterwhite CL, Torrone E, Meites E, et al. Sexually transmitted infections among US women and men: prevalence and incidence estimates, 2008. Sex Transm Dis 2013;40:187–93. CrossRef PubMed

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Return to your place in the textTABLE 1. Rates and rate ratios for primary and secondary syphilis among men who have sex with men (MSM), among men who have sex with women only, and among women, by state and overall — United States, 2015*
StateMSMRate of primary and secondary syphilis per 100,000 populationRate ratio§
Estimated no. in population% of all menMSMMen who have sex with women onlyWomenMSM compared with men who have sex with women onlyMSM compared with women
Overall3,921,5153.8309.02.91.8106.0167.5
Alabama41,8222.3320.42.41.9131.5169.4
Alaska5,4691.973.11.10.467.8189.5
Arizona112,1024.5385.43.31.7116.1222.0
Arkansas19,1011.7314.13.42.292.9140.6
California796,9265.5332.23.93.185.8108.0
Colorado74,7423.6248.91.20.2205.51,023.7
Connecticut43,5423.2112.50.71.0162.7117.6
Florida351,7974.6370.14.52.482.7152.3
Hawaii15,7072.8388.41.10.2342.12,140.3
Idaho9,9791.7320.72.41.3131.0242.7
Illinois199,0754.1311.92.51.5124.6203.8
Indiana72,4133.0290.01.51.1193.3266.6
Iowa20,9241.8219.81.00.4226.7531.7
Kansas21,9062.0228.21.31.4169.6168.1
Kentucky47,5762.9159.71.91.384.5126.8
Louisiana43,2042.5601.88.49.571.963.7
Maine14,3752.8118.30.41.1295.3108.9
Maryland83,6683.8325.14.52.472.0137.9
Massachusetts110,2544.3278.41.10.9247.3324.2
Michigan116,3543.1233.81.40.8163.8280.2
Minnesota82,5104.0147.93.81.739.287.0
Mississippi20,1841.9658.94.12.6161.0251.3
Missouri72,8753.2204.53.82.253.993.0
Montana6,8001.7132.40.50.0254.1
Nevada51,9904.8398.24.91.881.3216.6
New Hampshire13,8682.7187.51.20.6155.3337.8
New Jersey136,2714.1152.61.30.7117.2219.3
New Mexico18,6752.4428.42.51.4169.2314.0
North Carolina105,7072.9748.35.32.7140.0278.2
North Dakota4,8401.7165.31.10.0150.4
Ohio146,0333.4214.32.91.473.3157.5
Oklahoma37,0062.6418.92.31.4185.4297.6
Oregon60,9324.0313.52.82.2111.9142.1
Pennsylvania162,8483.3256.11.60.8159.3310.5
Rhode Island24,7456.1226.32.70.984.6248.9
South Carolina35,3882.0536.92.91.7187.8307.9
South Dakota4,9371.5405.12.62.2156.2186.2
Tennessee73,4603.0325.32.80.9115.4371.3
Texas378,3103.9289.43.22.290.1133.9
Utah33,8983.3132.80.50.2251.1679.2
Vermont7,1422.9126.00.00.0
Virginia115,5153.7210.41.50.5138.3436.0
Washington113,5044.2306.61.91.1160.6290.6
West Virginia13,1411.8197.92.31.287.2165.0

* Data based on 2015 cases reported to CDC by June 8, 2016.
To optimize stability of the estimates, the analysis was limited to the 44 states that included sex of sex partner in ≥70% of male primary and secondary syphilis case reports for 2015.
§ Rate ratios were calculated as 1) the rate of primary and secondary syphilis among MSM divided by the rate among men who have sex with women only and 2) the rate among MSM divided by the rate among women. In this report “women” is used to describe both females aged ≥18 years (used for calculating rates for women), and females of unknown ages (used for calculating rates for men who had sex with women only). Rate ratios were rounded to tenths.
Montana, North Dakota, and Vermont had no cases of primary and secondary syphilis reported among women for 2015, resulting in an undefined rate ratio comparing MSM with women. Vermont had no cases of primary and secondary syphilis reported among men who had sex with women only in 2015, resulting in an undefined rate ratio comparing MSM with men who have sex with women only..

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Return to your place in the textTABLE 2. States ranked from highest to lowest, by rates of primary and secondary syphilis cases overall and among men who have sex with men (MSM) and men who have sex with women only, and by rate ratios comparing the rates for MSM with the rates for men who have sex with women only and the rates for women — United States, 2015*
Rank     Rate of primary and secondary syphilis per 100,000 population     Rate ratio§
     Overall primary and secondary syphilis     Primary and secondary syphilis among MSM     Primary and secondary syphilis among men who have sex with women onlyMSM compared with men who have sex with women only     MSM compared with women
1     Louisiana     North Carolina     Louisiana     Hawaii     Hawaii
2     California     Mississippi     North Carolina     Maine     Colorado
3     North Carolina     Louisiana     Nevada     Montana     Utah
4     Nevada     South Carolina     Maryland     Utah     Iowa
5     Florida     New Mexico     Florida     Massachusetts     Virginia
6     Arizona     Oklahoma     Mississippi     Iowa     Tennessee
7     Oregon     South Dakota     California     Colorado     New Hampshire
8     Maryland     Nevada     Missouri     Indiana     Massachusetts
9     Illinois     Hawaii     Minnesota     South Carolina     New Mexico
10     Mississippi     Arizona     Arkansas     Oklahoma     Pennsylvania
11     Rhode Island     Florida     Arizona     Kansas     South Carolina
12     Hawaii     California     Texas     New Mexico     Oklahoma
13     Washington     Tennessee     Ohio     Michigan     Washington
14     Texas     Maryland     South Carolina     Connecticut     Michigan
15     Massachusetts     Idaho     Tennessee     Mississippi     North Carolina
16     South Carolina     Alabama     Oregon     Washington     Indiana
17     Alabama     Arkansas     Rhode Island     Pennsylvania     Mississippi
18     New Mexico     Oregon     South Dakota     South Dakota     Rhode Island
19     Oklahoma     Illinois     New Mexico     New Hampshire     Idaho
20     Tennessee     Washington     Illinois     North Dakota     Arizona
21     Pennsylvania     Indiana     Idaho     North Carolina     New Jersey
22     Missouri     Texas     Alabama     Virginia     Nevada
23     Ohio     Massachusetts     West Virginia     Alabama     Illinois
24     Colorado     Pennsylvania     Oklahoma     Idaho     Alaska
25     South Dakota     Colorado     Washington     Illinois     South Dakota
26     Arkansas     Michigan     Kentucky     New Jersey     Alabama
27     Minnesota     Kansas     Pennsylvania     Arizona     Kansas
28     Indiana     Rhode Island     Virginia     Tennessee     West Virginia
29     New Jersey     Iowa     Indiana     Oregon     Ohio
30     Michigan     Ohio     Michigan     Arkansas     Florida
31     Virginia     Virginia     Kansas     Texas     Oregon
32     Idaho     Missouri     New Jersey     West Virginia     Arkansas
33     Kentucky     West Virginia     Colorado     California     Maryland
34     New Hampshire     New Hampshire     New Hampshire     Rhode Island     Texas
35     Kansas     North Dakota     Hawaii     Kentucky     Kentucky
36     West Virginia     Kentucky     Massachusetts     Florida     Connecticut
37     Connecticut     New Jersey     North Dakota     Nevada     Maine
38     Iowa     Minnesota     Alaska     Ohio     California
39     Utah     Utah     Iowa     Maryland     Missouri
40     Maine     Montana     Connecticut     Louisiana     Minnesota
41     North Dakota     Vermont     Utah     Alaska     Louisiana
42     Vermont     Maine     Montana     Missouri     —
43     Montana     Connecticut     Maine     Minnesota     —
44     Alaska     Alaska     Vermont     —     —

* Data based on 2015 cases reported to CDC by June 8, 2016.
To optimize stability of the estimates, the analysis was limited to the 44 states that included the sex of sex partners in ≥70% of male primary and secondary syphilis case reports for 2015.
§ Rate ratios were calculated as 1) the rate of primary and secondary syphilis among MSM divided by the rate among men who have sex with women only and 2) the rate among MSM divided by the rate among women. In this report “women” is used to describe both females aged ≥18 years (used for calculating rates for women), and females of unknown ages (used for calculating rates for men who had sex with women only).
Montana, North Dakota, and Vermont had no cases of primary and secondary syphilis reported among women for 2015, resulting in an undefined rate ratio comparing MSM with women. Vermont had no cases of primary and secondary syphilis reported among men who had sex with women only in 2015, resulting in an undefined rate ratio comparing MSM with men who have sex with women only..

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Suggested citation for this article: de Voux A, Kidd S, Grey JA, et al. State-Specific Rates of Primary and Secondary Syphilis Among Men Who Have Sex with Men — United States, 2015. MMWR Morb Mortal Wkly Rep 2017;66:349–354. DOI: http://dx.doi.org/10.15585/mmwr.mm6613a1.

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