Syphilis

Background

Syphilis, a genital ulcerative disease caused by the bacterium Treponema pallidum, is associated with significant complications if left untreated and can facilitate the transmission and acquisition of HIV infection.^1–3 Additionally, historical data demonstrate that untreated early syphilis in pregnant women may result in perinatal death of the infant in up to 40% of cases and, if acquired during the 4 years before pregnancy, can lead to infection of the fetus in 80% of cases.⁴

In 2000 and 2001, the national rate of reported primary and secondary (P&S) syphilis cases was 2.1 cases per 100,000 population, the lowest rate since reporting began in 1941 (Figure 31, Table 1). However, the P&S syphilis rate has increased almost every year since 2000–2001. In 2014, a total of 19,999 P&S syphilis cases were reported, and the national P&S syphilis rate increased to 6.3 cases per 100,000 population, the highest rate reported since 1994.

During 2000–2014, the rise in the P&S syphilis rate was primarily attributable to increased cases among men and, specifically, among gay, bisexual, and other men who have sex with men (collectively referred to as MSM) (Figures 32 and 33). However, during 2013–2014, the rate increased both among men (14.4%) and among women (22.7%) (Tables 28 and 29). This increase among women is of particular concern because congenital syphilis cases tend to increase as the rate of P&S syphilis among women increases (Figure 46). During 2013–2014, the overall, male, and female P&S syphilis rates increased in every region of the country (Figure 34, Tables 27, 28, and 29). Nationally, P&S syphilis rates increased in every age group 15–44 years of age (Table 35) and in every race/ethnicity group except for Native Hawaiians/Other Pacific Islanders during 2013–2014 (Figure 40).

As in recent years, MSM accounted for the majority of P&S syphilis cases in 2014 (Figures 32 and 41). Nationally, the highest rates of P&S syphilis in 2014 were observed among men aged 20–24 years and 25–29 years (Figure 37, Table 35), among men in the West and in the South (Table 29), and among black men (Table 36B).

Interpreting Rates of Reported Cases of Syphilis

Left untreated, infection with syphilis can span decades. Primary and secondary syphilis are the earliest stages of infection, reflect symptomatic disease, and are indicators of incident infection.⁵ For these reasons, trend analyses of syphilis focus on reported cases and rates of reported cases of P&S syphilis. When referring to “P&S syphilis”, case counts are the sum of both primary and secondary cases, and “rate of P&S syphilis” refers to this sum per unit population. Changes in reporting and screening practices can complicate interpretation of trends over time. To minimize the effect of changes in reporting over time, trend data in this report are restricted to jurisdictions that consistently report data of interest (e.g., sex of sex partner) for each year of a given time period. Details of these restrictions are provided in the text and footnotes of the pertinent text and figures.

P&S Syphilis — United States

In 2014, a total of 19,999 cases of P&S syphilis were reported in the United States, yielding a rate of 6.3 cases per 100,000 population (Table 1). This rate represents a 15.1% increase compared with 2013 (5.5 cases per 100,000 population), and a 40.0% increase compared with 2010 (4.5 cases per 100,000 population).

P&S Syphilis by Region

In 2014, the West had the highest rate of reported P&S syphilis cases (7.9 cases per 100,000 population), followed by the South (6.9 cases per 100,000 population), the Northeast (5.5 cases per 100,000 population), and the Midwest (4.4 cases per 100,000 population) (Table 27). During 2013–2014, the P&S syphilis rate increased in every region: 17.9% in the West, 16.9% in the South, 14.6% in the Northeast, and 10.0% in the Midwest
(Figure 34, Table 27).

P&S Syphilis by State

In 2014, rates of reported P&S syphilis cases per 100,000 population ranged by state from 0.7 in Wyoming to 12.8 in Nevada; the P&S syphilis rate in the District of Columbia was 17.9 cases per 100,000 population (Figure 35, Table 26). During 2013–2014, P&S syphilis rates increased in 70% (35/50) of states and in the District of Columbia, and decreased in 30% (15/50) of states (Table 27).

P&S Syphilis by Metropolitan Statistical Area

The overall rate of reported P&S syphilis cases in the 50 most populous metropolitan statistical areas (MSAs) was 8.7 cases per 100,000 population in 2014, which represents a 13.0% increase since 2013 (7.7 cases per 100,000 population) (Table 30). In 2014, 74.9% of reported P&S syphilis cases (76.5% of male cases and 59.5% of female cases) were reported by these 50 MSAs. In 2014, the rate among women in these MSAs was 1.2 cases per 100,000 females, while the rate among men was 16.4 cases per 100,000 males (Tables 31 and 32).

P&S Syphilis by County

In 2014, 67% of reported P&S syphilis cases occurred in just 70 counties or independent cities (Table 33). Of 3,142 counties in the United States, 411 (13.1%) had a rate greater than 5.4 cases per 100,000 population, 400 (12.7%) reported a rate from 2.5 to 5.4 cases per 100,000 population, 389 (12.4%) reported a rate between 0.3 and 2.4 cases per 100,000 population, and 1,942 (61.8%) counties reported no cases of P&S syphilis in 2014 (Figure 36).

P&S Syphilis by Sex and Sex Behavior

As has been observed in previous years, in 2014 the rate of reported P&S syphilis cases among men (11.7 cases per 100,000 males) was much higher than the rate among women (1.1 cases per 100,000 females), and men account for a large majority (90.8%) of P&S syphilis cases with known sex (Figure 37, Tables 28 and 29). Among men, the rate of P&S syphilis has increased every year since 2000, and during 2013–2014 the rate among men increased 14.4% (Figure 33). In contrast, the P&S syphilis rate among women has fluctuated between 0.8 and 1.7 cases per 100,000 females since 2000. During 2013–2014, the P&S syphilis rate among women increased 22.7%.

These increases in male and female P&S syphilis rates were observed in every region of the country during 2013–2014. Among men, the rate increased 17.0% in the South, 15.9% in the West, 15.1% in the Northeast, and 6.8% in the Midwest (Table 29). Among women, the largest increases were observed in the West (50%), followed by the Midwest (28.5%), Northeast (25.0%), and South (7.1%).

MSM continued to account for the majority of P&S syphilis cases in 2014 (Figures 32 and 41). Of 19,999 P&S reported syphilis cases in 2014, 12,226 (61.1%) were among MSM, 2,513 (12.6%) were among men who have sex with women only (MSW), 1,840 (9.2%) were among women, 3,407 (17.0%) were among men without information about sex of sex partner, and 13 (0.1%) were cases reported with unknown sex (Figure 41). Among male cases with information on sex of sex partner, 82.9% occurred among MSM.

This same pattern was observed across race/ethnicity groups: the majority of P&S syphilis cases among whites, blacks, and Hispanics in 2014 occurred among MSM (Figure 42). Among MSM, the largest proportion of P&S syphilis cases in 2014 occurred among whites (37.6%), followed by blacks (31.8%) and Hispanics (21.8%). In contrast, the largest proportion of cases among MSW and women occurred among blacks (48.4% of cases among MSW and 50.0% of cases among women).

A total of 27 states reported sex of sex partner data for at least 70% of reported P&S cases each year during 2007–2014. In these states during 2013–2014, the number of cases increased 8.8% among MSM, 16.3% among MSW, and 28.1% among women. (Figure 32).

P&S Syphilis by Age

As in previous years, in 2014 rates of reported P&S syphilis cases were highest among persons aged 20–24 years and 25–29 years (Figure 37, Table 35). In 2014, the highest rates were observed among men aged 25–29 years (34.0 cases per 100,000 males) and 20–24 years (31.1 cases per 100,000 males). Similarly, the highest rates among women were among those aged 25–29 years (4.5 cases per 100,000 women) and those aged 20–24 years (2.5 cases per 100,000 women).

During 2013–2014, the P&S syphilis rate increased among all age groups aged 15–64 years (Table 35). Rates increased 11.6% among persons aged 15–19 years, 13.1% among persons aged 20–24 years, 23.4% among those aged 25–29 years, 18.3% among those aged 30–34 years, 13.0% among those aged 35–39 years, 3.7% among those aged 40–44 years, 13.3% among those aged 45–54 years, and 21.1% among those aged 55–64 years (Table 35).

In 2014, persons aged 15–44 years accounted for 79.7% of reported P&S syphilis cases with known age. Among men, the P&S syphilis rate increased during 2013–2014 among all age groups 15–44 years of age (Figure 39). Among women, the P&S syphilis rate remained stable among those aged 40–44 years, but increased among all age groups 15–39 years of age (Figure 38).

P&S Syphilis by Race/Ethnicity

In 2014, among the 49 states that submitted data in the race and ethnicity categories according to Office of Management and Budget (OMB) standards (see Section A1.5 in the Appendix), the rate of reported P&S syphilis cases remained highest among blacks (18.9 cases per 100,000 population) (Table 36B). The rate among blacks was 5.4 times the rate among whites (3.5 cases per 100,000 population). The P&S syphilis rates among American Indians/Alaska Natives (7.6 cases per 100,000 population) and Hispanics (7.6 cases per 100,000 population) were 2.2 times the rate among whites, the rate among Native Hawaiians/Other Pacific Islanders (6.5 cases per 100,000 population) was 1.9 times the rate among whites, and the rate among Asians (2.8 cases per 100,000 population) was 0.8 times the rate among whites.

During 2010–2014, among the 44 states that submitted race and ethnicity data according to OMB standards (see Section A1.5 in the Appendix) for all five years during that period, the P&S syphilis rate increased among all race/ethnicity groups (Figure 40). During 2013–2014, rates increased in every race/ethnicity group except for Native Hawaiians/Other Pacific Islanders. The greatest increases during 2013–2014 were observed among American Indians/Alaska Natives (68.8%) and those who identified as multiracial (47.3%), followed by Hispanics (15.7%), whites (14.3%), Asians (12.8%), and blacks (11.4%).

More information on P&S syphilis rates among race/ethnicity groups can be found in the Special Focus Profiles.

P&S Syphilis and HIV Co-infection

Reported cases of P&S syphilis continue to be characterized by a high rate of HIV co-infection, particularly among MSM. In 2014, 26 states reported both sex of sex partner and HIV status (HIV-positive or HIV-negative) for at least 70% of P&S syphilis cases (Figure 43). Among P&S syphilis cases with known HIV-status in these states, 51.2% of cases among MSM were HIV-positive, compared with 10.7% of cases among MSW, and 5.9% of cases among women.

P&S Syphilis by Reporting Source

The number of P&S syphilis cases reported by STD clinics and by non-STD clinic settings increased during 2005–2014 (Figure 44). However, the proportion of P&S syphilis cases that were reported by STD clinics declined during this period, from 31.3% of cases with known reporting source in 2005 to 24.9% of cases in 2014 (Table A2). In 2014, STD clinics and private physicians or health maintenance organizations (HMOs) were the most common reporting sources among MSM (28.7% and 28.2%, respectively), MSW (25.7% and 23.3% of cases, respectively), and women (18.7% and 24.3%, respectively)(Figure 45).

Congenital Syphilis

After decreasing during 2008–2012 (from 10.5 to 8.4 reported cases per 100,000 live births), the rate of reported congenital syphilis increased in 2013 to 9.1 cases per 100,000 live births (Table 1). During 2013–2014, the rate increased 27.5% to 11.6 cases per 100,000 live births in 2014. As has been observed historically, this increase paralleled a similar increase (22.2%) in P&S syphilis among women during 2013–2014 (Figure 46).

In 2014, the highest congenital syphilis rates continued to be reported from the South (15.5 cases per 100,000 live births), followed by the West (12.6 cases per 100,000 live births, Midwest (8.5 cases per 100,000 live births), and the Northeast (4.7 cases per 100,000 live births). During 2013–2014, the congenital syphilis rate increased in every region, with the largest increases occurring in the Northeast (74.1%) and West (63.6%) compared with the Midwest (32.8%) and South (9.2%) (Table 42). Increased congenital syphilis rates were also observed among most race/ethnicity groups during 2013–2014, including whites (32.1%), blacks (21.6%), Hispanics (19.6%), and Asians/Pacific Islanders (102.9%) (Table 43).

Syphilis — All Stages (P&S, Early Latent, Late, Late Latent, and Congenital)

Total case counts and rates for syphilis were the highest recorded since 1995. The total number of cases of syphilis (P&S, early latent, late, late latent, and congenital) reported to CDC increased 12.3% during 2013–2014 (from 56,482 cases to 63,450 cases) (Table 1). The number of cases of early latent syphilis reported to CDC increased 14.8% (from 16,929 cases to 19,452 cases), and the number of cases of late and late latent syphilis increased 7.9% (from 21,819 cases to 23,541 cases) (Tables 1, 37, and 39).

Syphilis among Special Populations

More information about syphilis and congenital syphilis in race/ethnicity groups, women of reproductive age, adolescents, and MSM can be found in the Special Focus Profiles.

Syphilis Summary

The national rate of reported P&S syphilis cases reached an historic low in 2000 and 2001, but has increased almost every year since then. This increase was largely attributable to an increase among men, and in particular among MSM. However, during 2013–2014, rates increased among both men and women in every region of the country. Rates of reported congenital syphilis cases also increased in every region of the country during 2013–2014.

MSM continued to account for the majority of P&S syphilis cases in 2014. Nationally, the highest rates of P&S syphilis in 2014 were observed among men aged 20–24 years and 25–29 years, among men in the West and in the South, and among black men.

     

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1 Jarzebowski W, Caumes E, Dupin N, et al. Effect of early syphilis infection on plasma viral load and CD4 cell count in human immunodeficiency virus-infected men: results from the FHDH-ANRS CO4 cohort. Arch Intern Med 2012; 172: 1237–1243.

2 Buchacz K, Patel P, Taylor M, et al. Syphilis increases HIV viral load and decreases CD4 cell counts in HIV-infected patients with new syphilis infections. AIDS 2004; 18:2075–2079.

3 Fleming DT, Wasserheit JN. From epidemiological synergy to public health policy and practice: the contribution of other sexually transmitted diseases to sexual transmission of HIV infection. Sex Trans Infect 1999; 75: 3–17.

4 Ingraham NR. The value of penicillin alone in the prevention and treatment of congenital syphilis. Acta Derm Venereol 1951; 31(Suppl 24): 60–88.

5 Peterman TA, Kahn RH, Ciesielski CA, Ortiz-Rios E, Furness BW, Blank S, et al. Misclassification of the stages of syphilis: implications for surveillance. Sex Transm Dis. 2005;32(3):144-9.

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