Surveillance for Primary and Secondary Syphilis -- United States, 1991

Linda A. Webster, Ph.D. Robert T. Rolfs, M.D. Division of Sexually Transmitted Diseases and HIV Prevention National Center for Prevention Services

Abstract

Problem/Condition: From 1986 through 1990, an epidemic of syphilis occurred throughout the United States. In 1991, the number of reported cases of primary and secondary (P&S) syphilis in the United States declined for the first time since 1985.

Reporting Period Covered: To examine how this decline reflected sex-specific, race/ethnicity-specific, and regional patterns of syphilis morbidity, we analyzed data for syphilis cases reported to CDC from 1984 through 1991.

Description of System: Summary data for cases of syphilis reported to state health departments were sent quarterly and annually to CDC. The quarterly data from each state included total number of syphilis cases by sex, stage of disease (primary, secondary, early latent, and late latent), and source of report (public or private). The annual data from each state included total number of P&S syphilis cases by sex, racial/ethnic group (white, not of Hispanic origin; black, not of Hispanic origin; Hispanic; Asian/Pacific Islander; or American Indian/Alaskan Native), 5-year age group, and source of report.

Results: The decline in both the number and rate of reported syphilis cases in 1991 occurred in every racial group in the United States and in both sexes. This decline also occurred in every region of the United States except the Midwest, where the total P&S syphilis rate increased 37.3% from 1990 through 1991. Despite the increase in syphilis rates in the Midwest, the highest rates of P&S syphilis in 1991 were reported from the South.

Interpretation: The reasons for the decline in syphilis are unclear. No data exist to conclusively identify which STD control program activities affected the level of syphilis morbidity or to what extent those activities may have contributed to the decline. Changes in drug use and limited immunity to Treponema pallidum may have accounted for some of the decrease in syphilis incidence. Higher levels of poverty in the South and poor access to health-care services associated with poverty probably contributed to continued high levels of disease transmission in the South.

Actions Taken: Better evaluation of STD control program activities will be necessary to help determine the most effective strategies for preventing and controlling syphilis in different high-risk populations.

INTRODUCTION

From 1986 through 1990, an epidemic of syphilis occurred throughout the United States. In 1990, more than 50,000 cases of primary and secondary (P&S) syphilis were reported, the highest number of cases since 1948. However, in 1991, the number of reported cases of P&S syphilis in the United States declined for the first time since 1985. A total of 42,943 cases of P&S syphilis were reported, representing a 15% decline from the number of cases reported in 1990. The purpose of this analysis is to a) examine how this decline reflected different sex-specific, race/ethnicity-specific, and regional patterns of syphilis morbidity; b) discuss possible reasons for the decline; and c) identify where the highest rates of syphilis occurred in 1991.

METHODS

Summary data for cases of syphilis reported to state health departments from 1984 through 1991 were sent quarterly and annually to CDC. The quarterly data from each state included total number of syphilis cases by sex, stage of disease (primary, secondary, early latent, and late latent), and source of report (public, private). The annual data from each state included total number of P&S syphilis cases by sex, racial/ethnic group (white, not of Hispanic origin; black, not of Hispanic origin; Hispanic; Asian/Pacific Islander; or American Indian/Alaskan Native), 5-year age group, and source of report (public or private). Data were analyzed by race/ethnicity so that prevention efforts can be targeted for the needs of specific groups.

P&S rates were calculated by using estimates of the population for 1984 through 1989, as well as data from the 1990 census for 1990 and 1991 (1,2). To compute regional rates of P&S syphilis, states were grouped into the four regions of the United States as defined by the Bureau of the Census: Northeast (Connecticut, Maine, Massachusetts, New Hampshire, New Jersey, New York, Pennsylvania, Rhode Island, Vermont); South (Alabama, Arkansas, Delaware, District of Columbia, Florida, Georgia, Kentucky, Louisiana, Maryland, Mississippi, North Carolina, Oklahoma, South Carolina, Tennessee, Texas, Virginia, West Virginia); Midwest (Illinois, Indiana, Iowa, Kansas, Michigan, Minnesota, Missouri, Nebraska, North Dakota, Ohio, South Dakota, Wisconsin); and West (Alaska, Arizona, California, Colorado, Hawaii, Idaho, Montana, Nevada, New Mexico, Oregon, Utah, Washington, Wyoming).

RESULTS

In 1991, 42,943 cases of P&S syphilis were reported to CDC (Table 1). That number represented a 15% decrease from the 50,578 cases reported in 1990 and the first decrease since 1985. The rate of P&S syphilis in the United States also declined from 20.3 cases per 100,000 population in 1990 to 17.3 in 1991. The male-to-female P&S rate ratio decreased steadily from 1984 through 1991, reflecting the larger percentage increase in rates among females during the epidemic period and the smaller percentage decrease in rates among females from 1990 through 1991.

In 1991, the male-to-female P&S rate ratio was highest among Hispanics (1.7), intermediate among whites (1.5), and lowest among blacks (1.3) (Table 2). The P&S syphilis rates for all race/ethnicity-sex groups were lower in 1991 than in 1990. However, the P&S rates among blacks continued to be much higher than the rates among whites and Hispanics. Specifically, the 1991 P&S syphilis rate among blacks was approximately 10 times higher than the rate among Hispanics and more than 60 times higher than the rate among whites.

Early latent syphilis rates declined somewhat less than P&S syphilis rates from 1990 through 1991 (Table 3). Specifically, early latent syphilis rates declined 2.7% from 22.3 cases per 100,000 population in 1990 to 21.7 in 1991. Early latent syphilis was more common among females than males (22.4 cases per 100,000 population in females vs. 20.9 in males). Consequently, rates of all early syphilis (primary, secondary, and early latent) were almost the same for males and females.

The 1991 P&S syphilis rates were lower than the 1990 rates in all regions of the United States except the Midwest (Table 4). In the Midwest, the 1991 total P&S syphilis rate of 10.3 per 100,000 population was 37.3% higher than the 1990 rate of 7.5. From 1990 through 1991, the total P&S syphilis rate decreased 32.6% in the Northeast, 11% in the South, and 41.6% in the West. Despite the increase in P&S syphilis in the Midwest and the decrease in all other regions, the South continued to have the highest rates of syphilis in 1991. Specifically, the 1991 P&S syphilis rate in the South of 30.0 cases per 100,000 population was almost twice the rate in the Northeast, almost three times the rate in the Midwest, and 4.5 times the rate in the western region of the United States.

In 1991, the highest rates of P&S syphilis were reported from states in the South: Louisiana (70.0 cases per 100,000 population), Mississippi (48.0), Georgia (45.6), South Carolina (43.8), and Alabama (39.4) (Table 5). Approximately 81% of the states in the South had P&S rates higher than the Year 2000 objective of 10 cases per 100,000 population, compared with 44% of the states in the Northeast, 33% of the states in the Midwest, and no states in the West. In 1991, the highest rates in the Northeast were reported from New York (21.3 cases per 100,000 population), the highest rates in the Midwest from Illinois (21.4), and the highest rates in the West from Arizona (9.1) and California (9.0).

DISCUSSION

The 42,943 cases of P&S syphilis reported in 1991 represented the first decline in the number of reported syphilis cases since 1985. This decline in both the number and rate of reported syphilis occurred in every race/ethnicity-sex group in the United States. The decline was observed in every region of the United States except the Midwest, where the total P&S syphilis rate increased 37.3% from 1990 through 1991. Despite the increase in syphilis rates in the Midwest, the highest rates of P&S syphilis in 1991 were reported from the South.

These findings are consistent with previous analyses of the regional trends in syphilis in the United States in the latter half of the 1980s (3). The biggest declines in P&S rates were in the West, where the epidemic occurred earlier (beginning in 1986 and peaking in 1987) and where rates were below the pre-epidemic level by 1991. In contrast, in the Midwest, where the epidemic began later (1988), rates continued to increase in 1991. The 1991 decrease in P&S rates in the South and Northeast represented the first decreases since the epidemic began in those regions in 1987.

The reasons for the current decline in syphilis rates are unclear. A renewed priority and increased resources were given to syphilis control programs after the epidemic was recognized in the mid-1980s. The activities of STD control programs during the epidemic period included traditional approaches such as partner notification, as well as alternative approaches, including an emphasis on risk reduction through counseling and education and targeted screening and prevention efforts in specific communities and for specific populations (4-6). However, no data exist to conclusively identify which of these STD control program activities affected the level of syphilis morbidity or to what extent those activities may have contributed to the decline.

A change in some underlying factor may have affected disease transmission and contributed to the observed decline in syphilis. For example, drug use, in particular crack cocaine use, was found in a number of studies to be associated with an increased risk of sexually transmitted infections (7-9). Drug use appeared to mediate high-risk behaviors such as the exchange of sex for drugs or money. Thus, a decline in crack cocaine use or a change in patterns of its use could have resulted in a decline in these high-risk behaviors and a consequent decline in syphilis morbidity.

Little is known about why primary and secondary syphilis rates in the South have continued to be highest among all regions of the United States. Several studies have indicated that poverty is highly correlated with syphilis rates (10-13). Historically, among the four regions of the United States, the South has had a disproportionately large share of the population with incomes below the poverty level. More than 38% of the total U.S. population below the poverty level lived in the South in 1991 (14). The poor often have reduced access to health-care services and use them less, which in turn leads to delays in treatment and longer durations of untreated infection (15). These factors probably contributed to continued high levels of disease transmission in the South.

Although syphilis declined in the United States in 1991, incidence remains high in minority populations and in the South and has continued to increase in the Midwest. In addition, the prevalence of untreated infection will remain high in reproductive-aged women after incidence has begun to decline, leading to continuing high risk for congenital syphilis. If STD programs are to meet the challenge of reducing the continued high rates of syphilis in these populations in the 1990s, STD control program activities must be better evaluated. More specifically, meaningful measures of program activity that can be correlated with disease trends will assist in determining the most effective strategies for preventing and controlling syphilis in different high-risk populations.

References

1. Bureau of the Census. United States population estimates by age, sex, and state: 1981-1989. Current Population Reports (Series P-25). In press.

2. Bureau of the Census. Census of population and housing, 1990: summary tape file 1 {machine-readable file}. Washington: Bureau of the Census, 1991.

3. Webster LA, Rolfs RT, Nakashima AK, Greenspan JR. Regional and temporal trends in the surveillance of syphilis, United States, 1986-1990. In: CDC Surveillance Summaries, December 1991. MMWR 1991;40(No.SS-3):29-33.

4. CDC. Epidemic early syphilis -- Escambia County, Florida, 1987 and July 1989 - June 1990. MMWR 1991;40:323-5.

5. CDC. Alternative case-finding methods in a crack-related syphilis epidemic-Philadelphia. MMWR 1991;40:77-81,87.

6. CDC. Epidemic early syphilis -- Alabama, 1990-1991. MMWR 1992;41:790-4.

7. Rolfs RT, Goldberg M, Sharrar RG. Risk factors for syphilis: cocaine use and prostitution. Am J Public Health 1990;80:853-7.

8. CDC. Relationship of syphilis to drug use and prostitution -- Connecticut and Philadelphia, PA. MMWR 1988;37:755-8.

9. Marx R, Aral SO, Rolfs RT, et al. Crack, sex, and STD. Sex Transm Dis 1991;18:92-9. 

10. Nakashima AK, Rolfs RT, Ladan AI. Trends in the urban and rural distribution of primary and secondary syphilis, United States, 1986-1990. Presented at the Annual Meeting of International Society for Sexually Transmitted Diseases Research. Banff, British Columbia, Canada, October 1991. 

11. Bowdoin CD, Henderson CA, Davis WT, Morse JW, Remein QR. Socioeconomic factors in syphilis prevalence, Savannah, Georgia. J Vener Dis Infect 1945;30:131-9. 

12. Clarke EG. Studies on syphilis in the eastern health district of Baltimore city: prevalence in 1939 by race, sex, age, and socioeconomic status. Am J Syph 1945;29:455-73. 

13. Morton WE, Horton HB, Baker HW. Effects of socioeconomic status on incidences of three sexually transmitted diseases. Sex Transm Dis 1979;6:206-10. 

14. Bureau of the Census. Current population reports. Series P-60, No. 181. Poverty in the United States: 1991, US Government Printing Office, Washington, DC, 1992. 

15. Aral SO, Holmes KK. Epidemiology of sexual behavior and sexually transmitted diseases. In: Holmes KK, Mardh PA, Sparling PF, et al., eds. Sexually transmitted diseases. 2nd ed. New York: McGraw-Hill, 1990:19-36.

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