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


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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).

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.§


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.


* 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.

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
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*
State MSM Rate of primary and secondary syphilis per 100,000 population Rate ratio§
Estimated no. in population % of all men MSM Men who have sex with women only Women MSM compared with men who have sex with women only MSM compared with women
Overall 3,921,515 3.8 309.0 2.9 1.8 106.0 167.5
Alabama 41,822 2.3 320.4 2.4 1.9 131.5 169.4
Alaska 5,469 1.9 73.1 1.1 0.4 67.8 189.5
Arizona 112,102 4.5 385.4 3.3 1.7 116.1 222.0
Arkansas 19,101 1.7 314.1 3.4 2.2 92.9 140.6
California 796,926 5.5 332.2 3.9 3.1 85.8 108.0
Colorado 74,742 3.6 248.9 1.2 0.2 205.5 1,023.7
Connecticut 43,542 3.2 112.5 0.7 1.0 162.7 117.6
Florida 351,797 4.6 370.1 4.5 2.4 82.7 152.3
Hawaii 15,707 2.8 388.4 1.1 0.2 342.1 2,140.3
Idaho 9,979 1.7 320.7 2.4 1.3 131.0 242.7
Illinois 199,075 4.1 311.9 2.5 1.5 124.6 203.8
Indiana 72,413 3.0 290.0 1.5 1.1 193.3 266.6
Iowa 20,924 1.8 219.8 1.0 0.4 226.7 531.7
Kansas 21,906 2.0 228.2 1.3 1.4 169.6 168.1
Kentucky 47,576 2.9 159.7 1.9 1.3 84.5 126.8
Louisiana 43,204 2.5 601.8 8.4 9.5 71.9 63.7
Maine 14,375 2.8 118.3 0.4 1.1 295.3 108.9
Maryland 83,668 3.8 325.1 4.5 2.4 72.0 137.9
Massachusetts 110,254 4.3 278.4 1.1 0.9 247.3 324.2
Michigan 116,354 3.1 233.8 1.4 0.8 163.8 280.2
Minnesota 82,510 4.0 147.9 3.8 1.7 39.2 87.0
Mississippi 20,184 1.9 658.9 4.1 2.6 161.0 251.3
Missouri 72,875 3.2 204.5 3.8 2.2 53.9 93.0
Montana 6,800 1.7 132.4 0.5 0.0 254.1
Nevada 51,990 4.8 398.2 4.9 1.8 81.3 216.6
New Hampshire 13,868 2.7 187.5 1.2 0.6 155.3 337.8
New Jersey 136,271 4.1 152.6 1.3 0.7 117.2 219.3
New Mexico 18,675 2.4 428.4 2.5 1.4 169.2 314.0
North Carolina 105,707 2.9 748.3 5.3 2.7 140.0 278.2
North Dakota 4,840 1.7 165.3 1.1 0.0 150.4
Ohio 146,033 3.4 214.3 2.9 1.4 73.3 157.5
Oklahoma 37,006 2.6 418.9 2.3 1.4 185.4 297.6
Oregon 60,932 4.0 313.5 2.8 2.2 111.9 142.1
Pennsylvania 162,848 3.3 256.1 1.6 0.8 159.3 310.5
Rhode Island 24,745 6.1 226.3 2.7 0.9 84.6 248.9
South Carolina 35,388 2.0 536.9 2.9 1.7 187.8 307.9
South Dakota 4,937 1.5 405.1 2.6 2.2 156.2 186.2
Tennessee 73,460 3.0 325.3 2.8 0.9 115.4 371.3
Texas 378,310 3.9 289.4 3.2 2.2 90.1 133.9
Utah 33,898 3.3 132.8 0.5 0.2 251.1 679.2
Vermont 7,142 2.9 126.0 0.0 0.0
Virginia 115,515 3.7 210.4 1.5 0.5 138.3 436.0
Washington 113,504 4.2 306.6 1.9 1.1 160.6 290.6
West Virginia 13,141 1.8 197.9 2.3 1.2 87.2 165.0

* 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..

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 only MSM 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..

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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