Syphilis

Background

Syphilis, a genital ulcerative disease, causes significant complications if untreated and facilitates the transmission of HIV infection. Untreated early syphilis in pregnant women results in perinatal death 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.¹

The rate of primary and secondary (P&S) syphilis reported in the United States decreased during the 1990s; in 2000, the rate was the lowest since reporting began in 1941 (Figure 30). The low rate of P&S syphilis and the concentration of the majority of syphilis cases in a small number of geographic areas in the United States led to the development of CDC’s National Plan to Eliminate Syphilis, which was announced by the Surgeon General in October 1999 and revised in May 2006.²

Syphilis remains a major health problem, with increased cases occurring among gay, bisexual and other men who have sex with men (MSM). Cases among MSM have been characterized by high rates of HIV co-infection and high-risk sexual behaviors.^3–7 The estimated proportion of P&S syphilis cases attributable to MSM increased from 7% in 2000 to 64% in 2004.^8,9 In 2005, CDC requested that all state health departments report the sex of sex partners for persons with syphilis. Of reported male cases with P&S syphilis, sex of sex partner information in 2013 was available for 83%. In 2013, 49 states and the District of Columbia provided information about sex of sex partners. Among cases of P&S syphilis for whom sex of partner was known, MSM accounted for 75% of P&S syphilis cases.

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.¹⁰ For these reasons, trend analyses of syphilis focus upon cases and rates of reported cases of P&S syphilis. (When referred to as “P&S syphilis”, case counts are the sum of both primary and secondary cases, while the “rate of P&S syphilis” is this sum per unit population.) However, changes in reporting and screening practices can complicate interpretation of these trends. 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.

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

Total case counts and rates for syphilis were the highest recorded since 1996. The total number of cases of syphilis (P&S, early latent, late, late latent, and congenital) reported to CDC increased 13.1% during 2012–2013 (from 49,915 cases to 56,471 cases) (Table 1). The number of cases of early latent syphilis reported to CDC increased 16.7% (from 14,503 cases to 16,929 cases), and the number of cases of late and late latent syphilis increased 12.4% (from 19,411 cases to 21,819 cases) (Tables 1, 37, and 39).

P&S Syphilis — United States

Although the rate of P&S syphilis in the United States declined 89.7% during 1990–2000, the rate increased annually during 2001–2009 before decreasing in 2010 and remaining unchanged during 2011. The rate again increased during 2012 and 2013.

The case count and rate for P&S syphilis in 2013 was the highest recorded since 1995. The number of P&S syphilis cases reported to CDC increased from 15,667 in 2012 to 17,375 in 2013, an increase of 10.9%. The rate of P&S syphilis in the United States increased from 5.0 to 5.5 cases per 100,000 population (a 10.0% increase) during 2012–2013 (Table 1).

P&S Syphilis by Region

Each year since 2009, the rate of P&S syphilis has increased in the West. In 2013, for the first time in at least 50 years,¹¹ the rate in the West (6.8 cases per 100,000 population) exceeded the rate in the South (6.0 cases) (Figure 33). During 2012–2013, the rate of P&S syphilis increased 24.2% in the Midwest (from 3.3 to 4.1 cases), 19.3% in the West (from 5.7 to 6.8 cases), 11.6% in the Northeast (from 4.3 to 4.8 cases), and 3.4% in the South (from 5.8 to 6.0 cases per 100,000 population) (Figure 33, Table 27). The South continued to comprise the largest proportion of cases of P&S syphilis in 2013 (40%).

P&S Syphilis by State

In 2013, the 15 states and areas (including the District of Columbia) with the highest rates of P&S syphilis accounted for 70% of all U.S. cases of P&S syphilis. The rate of P&S syphilis in 14 of these 15 states and areas (including the District of Columbia) exceeded the national rate of 5.5 cases per 100,000 population; 9 of these 15 states and areas (including the District of Columbia) were in the South (Figure 34, Table 26).

P&S Syphilis by Metropolitan Statistical Area

The rate of P&S syphilis in 2013 for the 50 most populous MSAs (7.8 cases per 100,000 population) (Table 30) exceeded the overall rate for the United States (5.5 cases) (Table 27). The rate increased in 31 of these 50 MSAs (62%) during 2012–2013.

P&S Syphilis by County

Of 3,142 counties in the United States, counties reporting no cases of P&S syphilis decreased during 2012–2013, from 2,123 counties (67.6%) in 2012 to 2,029 counties (64.6%) in 2013 (Figure 35). In 2013, half of the total number of P&S syphilis cases was reported from 29 counties and two cities (Table 33).

P&S Syphilis by Sex

The rate of P&S syphilis increased 12.0% among men (from 9.2 to 10.3 cases per 100,000 men) during 2012–2013 (Figure 32, Table 29). During this same period, the rate among women remained unchanged (0.9 cases per 100,000 women) (Figure 32, Table 28).

P&S Syphilis by Age Group

In 2013, the rate of P&S syphilis was highest among persons aged 20–24 years and 25–29 years (16.1 and 15.6 cases per 100,000 population, respectively) (Table 35).

The rate of P&S syphilis decreased among women aged 15–19 years and 45–54 years (from 2.3 to 1.9 and from 0.6 to 0.5 cases per 100,000 population, respectively). The rate remained the same or increased for women of all other age groups. The rate remained highest among women aged 20–24 years (Figures 36 and 37, Table 35).

The rate of P&S syphilis was highest among men 20–29 years,  increasing 11.7% (from 24.8 to 27.7 cases) among men 20–24 years and 14.8% (from 24.4 to 28.0 cases) among men 25–29 years during 2012–2013 (Figures 36 and 38, Table 35). This marks the sixth consecutive year (2008–2013) that the rate of P&S syphilis among men has been highest among men aged 20–29 years (Table 35). During 2008–2013, the rate has increased among men aged 20–24 years by 60.1% (from 17.3 to 27.7 cases) and among men aged 25–29 years by 65.7% (from 16.9 to 28.0 cases). These data indicate a shift since 2006, when the rate was highest in men aged 35–39 years.

P&S Syphilis by Race/Ethnicity

In 2013, among the 48 jurisdictions (47 states and the District of Columbia) that submitted data in race and ethnicity categories according to the current Office of Management and Budget (OMB) standards, rates of P&S syphilis remained highest among blacks (16.8 cases per 100,000 population) (Table 36B). The rate among blacks was 5.6 times the rate among whites (3.0 cases per 100,000 population). The rate among American Indians/Alaska Natives (4.6) was 1.5 times that of whites, the rate among Native Hawaiians/Other Pacific Islanders (8.6) was 2.9 times that of whites, the rate among Hispanics (6.3) was 2.1 times that of whites, and the rate among Asians (2.5) was 0.8 times that of whites (Table 36B).

During 2009–2013, among the 40 jurisdictions (39 states and the District of Columbia) that submitted data in race and ethnic categories according to the current OMB standards for all five years during that period, the rate of P&S syphilis increased 65.3% among Hispanics (from 3.9 to 6.5 cases per 100,000 population), 42.5% among non-Hispanic whites (from 2.2 to 3.1 cases per 100,000 population), 77.2% among American Indians/Alaska Natives (from 2.8 to 5.0 cases per 100,000 population), 83.5% among Asians (from 1.4 to 2.7 cases per 100,000 population), 102.3% among Native Hawaiians/Other Pacific Islanders (from 4.8 to 9.6 cases per 100,000 population), and 113.8% among multirace individuals (from 0.9 to 1.8 cases per 100,000 population) (Figure 39). The rate decreased 7.4% among non-Hispanic blacks (from 18.7 to 17.3 cases per 100,000 population). Non-Hispanic blacks, non-Hispanic whites, and Hispanics comprised 95.0% of reported cases in 2009 and 92.3% of reported cases in 2013.

P&S Syphilis by Race/Ethnicity and Sex

In 2013, among the 48 jurisdictions (47 states and the District of Columbia) that submitted data in the race and ethnic categories according to OMB standards, rates of P&S syphilis among men were highest among non-Hispanic black men (30.2 cases per 100,000 population), followed by Native Hawaiian/Other Pacific Islander (15.8 cases per 100,000 population), Hispanic (11.6 cases per 100,000 population), American Indian/Alaska Native (7.1 cases per 100,000 population), non-Hispanic white (5.7 cases per 100,000 population), Asian (4.9 cases per 100,000 population) and multirace (3.4 cases per 100,000 population) men (Figure R, Table 36B).

Rates of P&S syphilis among women were highest among non-Hispanic black women (4.5 cases per 100,000 population), followed by American Indian/Alaska Native (2.1 cases per 100,000 population), Native Hawaiian/Other Pacific Islander (1.2 cases per 100,000 population), Hispanic (0.8 cases per 100,000 population), non-Hispanic white (0.3 cases per 100,000 population), multirace (0.3 cases per 100,000 population) and Asian (0.2 cases per 100,000 population) women (Figure R, Table 36B).

P&S Syphilis by Sex, Sex Behavior, and Race/Ethnicity

The male-to-female rate ratio for P&S syphilis rates rose steeply during 2000–2003 (from 1.5 to 5.3), and again during 2008–2013 (from 5.0 to 11.3), reflecting higher rates in men than women (Figure 32). In 2013, this ratio was more than double the ratio of 2003, and 7.5 times the ratio of 2000.

In 2005, CDC began collecting information on the sex of sex partners of patients with P&S syphilis. In 2013, this information was available for 83% of male cases. A higher proportion of MSW were reported with primary syphilis (39.3%) compared to women (20.7%) and MSM (29.4%) (Figure 40).

In 2013, most women with P&S syphilis were black (57.9%), while others were white (20.2%), Hispanic (14.0%), or of other races/ethnicities (4.1%). Most MSW were also black (52.6%), while others were white (20.9%), Hispanic (20.2%), or of other races/ethnicities (3.2%). MSM with P&S syphilis were of greater racial and ethnic diversity: 38.2% were white, 32.8% were black, 21.2% were Hispanic, and 4.9% were of other races/ethnicities (Figure 41).

During 2007–2013, 33 areas (32 states and Washington, D.C.) reported sex of partner data for at least 70% of cases each year during this time period (Figure 31). In these areas, increases in cases of P&S syphilis occurred among all individuals (women, men having sex with women only (MSW), and MSM) during 2007–2008. Among heterosexual individuals, cases decreased during 2008–2011 (18.4% among women and 25.9% among MSW), but increased during 2011–2013 (2.9% among women and 14.4% among MSW). Among MSM, cases increased annually during 2007–2013 (75%).

In 2013, 31 areas (30 states and District of Columbia) reported both sex of partner and human immunodeficiency virus (HIV) status (HIV-positive or HIV-negative) for 70% or more of reported cases of P&S syphilis. Among individuals with P&S syphilis, a higher proportion of MSM were HIV-positive (51.6%) compared to MSW (9.9%) or women (5.2%) (Figure 42).

P&S Syphilis by Race/Ethnicity, Age, and Sex

In 2013, among the 48 jurisdictions (47 states and the District of Columbia) that submitted data in the new race and ethnicity categories according to OMB standards, the rate of P&S syphilis among non-Hispanic blacks remained highest among women aged 20–24 years (17.0 cases per 100,000 women) and among men aged 20–24 years and 25–29 years (96.4 and 97.2 cases per 100,000 men, respectively). For Hispanics, the rate was highest among women aged 20–24 years and 25–29 years (2.5 and 2.1 cases per 100,000 women, respectively), and among men aged 20–24 years and 25–29 years (27.2 and 28.4 cases per 100,000 men, respectively). For non-Hispanic whites, the rate was highest among women aged 20–24 years (1.2 cases per 100,000 women) and among men aged 25–29 years and 30–34 years (12.6 and 11.8 cases per 100,000 men, respectively) (Table 36B).

For Asians, the rate was highest among women aged 20–24 years (1.0 cases per 100,000 women) and among men aged 20–24 years (13.1 cases per 100,000 men). For American Indians/Alaska Natives, the rate was highest among women aged 20–24 years (9.0 cases per 100,000 women) and among men aged 20–24 years and 25–29 years (18.3 and 16.7 cases per 100,000 men, respectively). For Native Hawaiians/Other Pacific Islanders, the rate was highest among women aged 15–19 and 35–39 years (5.3 cases and 5.6 cases per 100,000 women, respectively) and among men aged 25–29 years (59.7 cases per 100,000 men). For multirace individuals, rates were highest among women aged 30–34 years (1.2 cases per 100,000 women) and among men aged 25–29 years (10.4 cases per 100,000 men) (Table 36B).

In some age groups, particularly young men aged 20–24 years and 25–29 years, wide racial and ethnic disparities in rates of P&S syphilis have occurred in recent years.^9,12 In 2013, rates among men aged 20–24 years and 25–29 years remained highest among blacks (96.4 cases and 97.2 cases per 100,000 population, respectively). These rates were 8.9 and 7.7 times (respectively) the rates of white men of the same age groups. Large disparities were also seen with Native Hawaiian/Other Pacific Islander and Hispanic men, compared to white men. The 2013 rates among Native Hawaiian/Other Pacific Islander men aged 20–24 years and 25–29 years were 3.0 and 4.7 times the rates of white men of the same age groups. Likewise, 2013 rates among Hispanic men aged 20–24 years and 25–29 years were 2.5 and 2.3 times, respectively, the rates of white men of the same age group.

Racial and ethnic disparities in rates among men and women 15–19 years were also present in 2013. Rates among black men aged 15–19 years were 11.7 times the rate for white men and 3.2 times the rate for Hispanic men of the same age, and 2013 rates for black women aged 15–19 years were 18.2 times and 8.3 times the rate for white and Hispanic women of the same ages, respectively (Table 36B). The disparities in rates of P&S syphilis among young men are of particular concern given data indicating increasing HIV incidence among young MSM.¹³

P&S Syphilis by Reporting Source

In 1990, 25.6% of P&S syphilis cases were reported from sources other than STD clinics; this figure increased to 39.2% in 1998. During 1998–2013, the proportion of cases reported from sources other than STD clinics increased from 39.2% to 73.6% (Figure 43, Table A2). During 2004–2013, the number of cases among males reported from non-STD clinic sources increased steadily, while the number reported from STD clinics increased only slightly by comparison (Figure 43).

In 2013, patients with P&S syphilis were usually diagnosed by private physicians or STD clinics. Similar proportions of cases among MSM were reported from private physicians and STD clinics, while more cases among MSW were reported from STD clinics than from private physicians, and more cases among women were reported from private physicians than STD clinics (Figure 44).

Congenital Syphilis—United States and by Region

For the first time since 2008, the rate of congenital syphilis increased, from 8.4 (in 2012) to 8.7 (in 2013) cases per 100,000 live births (4%) (Table 1 and Table 42). This recent increase in the rate of congenital syphilis was largely driven by rate increases in the West (Table 42). This increase coincided with the increased rate of P&S syphilis in the West among females during 2010–2013 (Table 28).

Syphilis among Special Populations

More information about syphilis and congenital syphilis in racial and ethnic minority populations, adolescents, MSM, and other populations at higher risk can be found in the Special Focus Profiles.

Syphilis Summary

In recent years, the highest rates of P&S syphilis have occurred among young men. According to information reported from 49 states and the District of Columbia, 75% of P&S syphilis cases are among MSM. Although the majority of U.S. syphilis cases have occurred among MSM, transmission among MSW and women continues to occur in certain jurisdictions.

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

2 Centers for Disease Control and Prevention. The national plan to eliminate syphilis from the United States. Atlanta: U.S. Department of Health and Human Services; 2006.

3 Centers for Disease Control and Prevention. Resurgent bacterial sexually transmitted disease among men who have sex with men — King County, Washington, 1997–1999. MMWR Morb Mortal Wkly Rep. 1999;48:773-7.

4 Centers for Disease Control and Prevention. Outbreak of syphilis among men who have sex with men — Southern California, 2000. MMWR Morb Mortal Wkly Rep. 2001;50(7):117-20.

5 Centers for Disease Control and Prevention. Primary and secondary syphilis among men who have sex with men — New York City, 2001. MMWR Morb Mortal Wkly Rep. 2002;51:
853-6.

6 Chen SY, Gibson S, Katz MH, Klausner JD, Dilley JW, Schwarcz SK, et al. Continuing increases in sexual risk behavior and sexually transmitted diseases among men who have sex with men: San Francisco, California, 1999–2001 [Letter] Am J Public Health. 2002;92:1387-8.

7 D’Souza G, Lee JH, Paffel JM. Outbreak of syphilis among men who have sex with men in Houston, Texas. Sex Transm Dis. 2003;30:872-3.

8 Centers for Disease Control and Prevention. Primary and secondary syphilis — United States, 2003–2004. MMWR Morb Mortal Wkly Rep. 2006;55:269-73.

9 Heffelfinger JD, Swint EB, Berman SM, Weinstock HS. Trends in primary and secondary syphilis among men who have sex with men in the United States. Am J Public Health. 2007;97:1076-83.

10 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.

11 Centers for Disease Control and Prevention. Primary and secondary syphilis--United States, 2005–2013. MMWR Morb Mortal Wkly Rep. 2014 May 9;63(18):402-6.

12 Su JR, Beltrami JF, Zaidi AA, Weinstock HS. Primary and secondary syphilis among black and Hispanic men who have sex with men: case report data from 27 States. Ann Intern Med. 2011;155(3):145-51.

13 Centers for Disease Control and Prevention. Estimated HIV incidence in the United States, 2007–2010. HIV Surveillance Supplemental Report 2012;17(No. 4). Published December 2012.

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