Background

Syphilis, a genital ulcerative disease, causes significant complications if untreated and facilitates the transmission of HIV. Untreated early syphilis in pregnant women results in perinatal death in up to 40% of cases and, if acquired during the four years preceding pregnancy, may 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 26). The low rate of infectious 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 the CDC's National Plan to Eliminate Syphilis, which was announced by Surgeon General David Satcher in October 1999 and revised in May 2006.²

Although the rate of P&S syphilis in the United States declined 89.7% between 1990 and 2000, the rate of P&S syphilis increased between 2001 and 2006. Overall increases in rates between 2001 and 2006 were observed primarily among men (from 3.0 cases per 100,000 population to 5.7 cases per 100,000 population). After persistent declines since 1990, the rate of P&S syphilis among women increased from 0.8 cases per 100,000 population in 2004 to 0.9 cases per 100,000 population in 2005 to 1.0 case per 100,000 population in 2006.

Syphilis remains an important problem in the South and in urban areas in other regions of the country. Increases in cases among MSM have occurred and have been characterized by high rates of HIV co-infection and high-risk sexual behavior.^3-7 The estimated proportion of P&S syphilis cases attributable to MSM increased from 4% in 2000 to 62% in 2004.^8,9 In 2005, CDC requested that all state health departments report gender of sex partners for persons with syphilis. In 2006, the first full year for which data are available, 64% of all P&S syphilis cases from 30 areas (29 states and Washington, D.C.) with available information were among MSM.¹⁰

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

Between 2005 and 2006, the number of cases of early latent syphilis reported to CDC increased 12.4% (from 8,176 to 9,186), while the number of cases of late and late latent syphilis increased 9.9% (from 16,049 to 17,644) (Table 1). The total number of cases of syphilis (all stages: P&S, early latent, late, late latent, and congenital syphilis) reported to CDC increased 11.0% (from 33,288 to 36,935) between 2005 and 2006 (Table 1).

P&S Syphilis - United States

In 2006, P&S syphilis cases reported to CDC increased to 9,756 from 8,724 in 2005, an increase of 11.8%. The rate of P&S syphilis in the United States in 2006 (3.3 cases per 100,000 population) was 13.8% higher than the rate in 2005 (2.9 cases per 100,000 population), and it is greater than the HP 2010 target of 0.2 case per 100,000 population (Figure 27, Table 1).¹¹ Between 2005 and 2006, P&S syphilis rates in most age groups increased (Table 32).

P&S Syphilis by Region

The South accounted for 47.1% of the P&S syphilis cases in 2006 and 46.4% in 2005. Between 2005 and 2006, rates increased 13.2% in the South (from 3.8 to 4.3 cases per 100,000 population), 13.0% in the Northeast (from 2.3 to 2.6), and 15.2% in the West (from 3.3 to 3.8); rates remained the same in the Midwest (1.8). The 2006 rates in all regions were greater than the HP 2010 target of 0.2 cases per 100,000 population (Figure 28, Table 25).

P&S Syphilis by State

In 2006, P&S syphilis rates in four states were less than or equal to the HP 2010 target of 0.2 case per 100,000 population (Figure 29, Table 24). Five states and two outlying areas reported five or fewer cases of P&S syphilis in 2006 (Table 24).

P&S Syphilis by Metropolitan Statistical Area (MSA)

The rate of P&S syphilis in 2006 for the 50 most populous MSAs (4.9) exceeded the HP 2010 target of 0.2 case per 100,000 population (Table 29).

P&S Syphilis by County

In 2006, 2,360 of 3,140 counties (75.2%) in the United States reported no cases of P&S syphilis compared with 2,434 (77.5%) in 2005. Of 780 counties reporting at least one case of P&S syphilis in 2006, seven (0.9%) had rates at or below the HP2010 target of 0.2 case per 100,000 population. Rates of P&S syphilis were above the HP2010 target for 773 counties in 2006 (Figure 30). These 773 counties (24.6% of the total number of counties in the United States) accounted for 99.9% of the total P&S syphilis cases reported in 2006.

In 2006, half of the total number of P&S syphilis cases were reported from 20 counties and two cities (Table 28).

P&S Syphilis by Reporting Source

Between 1990 and 2006, the proportion of P&S syphilis cases reported from sources other than STD clinics increased from 25.6% to 65% (Figure 31, Table A2). Between 2001 and 2006, the number of cases among males reported from non-STD clinic sources increased sharply while the number from STD clinics remained stable (Figure 31).

P&S Syphilis by Age

In 2006, the rate of P&S syphilis was highest in persons in the 25- to 29-year-old age group (7.8 cases per 100,000 population) (Table 32).

P&S Syphilis by Race/Ethnicity

From 2005 to 2006, the rate of P&S syphilis increased in all racial and ethnic groups. The rate increased 5.6% among non-Hispanic whites (from 1.8 to 1.9), 16.5% among African Americans (from 9.7 to 11.3), 12.5% among Hispanics (from 3.2 to 3.6), 18.2% among Asian/Pacific Islanders (from 1.1 to 1.3), and 37.5% among American Indian/Alaska Natives (from 2.4 to 3.3) (Table 33B).

P&S Syphilis by Sex

The rate of P&S syphilis increased 11.8% among men (from 5.1 cases to 5.7 cases per 100,000 men) between 2005 and 2006 (Figure 27, Table 27). During this time, the rate increased 11.1% among women from 0.9 to 1.0 case per 100,000 women (Figure 27, Table 26).

P&S Syphilis by Male-to-Female Rate Ratio

The male-to-female rate ratio for P&S syphilis has risen steadily since 1996 when it was 1.2 (Figure 33), suggesting an increase in syphilis among MSM during this time. In 2006, the rate of syphilis in males was 5.7 times that in females.

Between 2005 and 2006, the male-to-female rate ratio for P&S syphilis increased among whites (from 11.0 to 11.7), African Americans (from 3.5 to 3.7), Hispanics (from 6.0 to 7.9), Asian/Pacific Islanders (from 11.0 to 25.0), and American Indian/Alaska Natives (from 2.1 to 2.5) (Table 33B).

An increase in the male-to-female rate ratio for P&S syphilis occurred in the District of Columbia, Puerto Rico, and in 20 of 34 states (59%) that reported at least 25 cases in 2006.

P&S Syphilis by Race/Ethnicity and Sex

From 2005 to 2006, the rate among non-Hispanic white males increased 6.1% (from 3.3 to 3.5), but remained the same among non-Hispanic white females (0.3). The rate increased 18.1% among African-American males (from 15.5 to 18.3) and 11.4% among African-American females (from 4.4 to 4.9). The rate increased 16.7% among Hispanic males (from 5.4 to 6.3), but decreased 11.1% among Hispanic females (from 0.9 to 0.8). The rate increased 13.6% among Asian/Pacific Island males (from 2.2 to 2.5), but decreased among Asian/Pacific Island females from 0.2 to 0.1. The rate increased 42.4% among American Indian/Alaska Native males (from 3.3 to 4.7) and 18.8% among American Indian/Alaska Native females (from 1.6 to 1.9) (Table 33B).

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

In 2006, the rate of P&S syphilis among African Americans was highest among women aged 20 to 24 years (14.9) and among men aged 25 to 29 years (48.8). For non-Hispanic whites, the rate was highest among women aged 25 to 29 years (0.8) and among men aged 35 to 39 years (9.9). For Hispanics, the rate was highest among women aged 25 to 29 years (1.9) and among men aged 35 to 39 years (14.6). For Asian/Pacific Islanders, the rate was highest among women aged 30 to 34 years (0.5) and among men aged 25 to 29 years (6.2). For American Indian/Alaska Natives, the rate was highest among women aged 35 to 39 years (6.1) and among men aged 30 to 34 years (12.8) (Table 33B).

Congenital Syphilis - United States

After 14 years of decline in the United States, the rate of congenital syphilis increased 3.7% between 2005 and 2006 (from 8.2 to 8.5 cases per 100,000 live births) (Figure 38, Table 39). In 2006, 349 cases were reported, an increase from 339 in 2005. This small increase in the rate of congenital syphilis (Figure 38) may relate to the increase in the rate of P&S syphilis among women that has occurred in recent years (Figure 37).

Between 1996 and 2005, the average yearly percentage decrease in the congenital syphilis rate was 14.1% (Figure 38). Overall, there has been a 74.2% decrease in the rate of congenital syphilis since 1996.

Congenital Syphilis by State

In 2006, 26 states, the District of Columbia, and one outlying area had rates of congenital syphilis that exceeded the HP 2010 target of one case per 100,000 live births (Table 38).

Syphilis Among Special Populations

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

Syphilis Summary

In recent years, MSM have accounted for an increasing number of estimated syphilis cases in the United States⁹ and now account for 64% of syphilis cases in the United States based on information available from 29 states and Washington, D.C.¹⁰ Given the recent request of CDC for states to collect and report gender of sex partners, it is expected that the availability and completeness of this information will increase. Despite the majority of U.S. syphilis cases occurring among MSM, heterosexual syphilis cases may be an emerging problem given the recent increases among women and infants.

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 CDC. The National Plan to Eliminate Syphilis from the United States. Atlanta, GA: U.S. Department of Health and Human Services, May 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 1999;48:773-777.

⁴ Centers for Disease Control and Prevention. Outbreak of syphilis among men who have sex with men – Southern California, 2000. MMWR 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 2002;51:853-6.

⁶ Chen SY, Gibson S, Katz MH, Klausner JD, Dilley JW, Schwarcz SK, Kellogg TA, McFarland W. 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. Sexually Transmitted Diseases 2003;30:872-3.

⁸ Centers for Disease Control and Prevention. Primary and secondary syphilis – United States, 2003-2004. MMWR 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;97:1076-1083.

¹⁰ Beltrami JF, Weinstock H.S. Primary and secondary syphilis among men who have sex with men in the United States, 2006. In: program and abstracts of the 17th Biennial meeting of the ISSTDR, Seattle, WA, July 29-August 1, 2007 [abstract O-069].

¹¹ U.S. Department of Health and Human Services. Healthy People 2010. 2nd ed. With Understanding and Improving Health and Objectives for Improving Health. 2 vols. Washington, DC: U.S. Government Printing Office, November 2000.

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Page last modified: November 13, 2007
Page last reviewed: November 13, 2007
Content Source: Division of STD Prevention, National Center for HIV/AIDS, Viral Hepatitis, STD, and TB Prevention