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Sexually Transmitted Diseases:
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Syphilis Outbreak Assessment

FINELLI, LYN DrPH; LEVINE, WILLIAM C. MD, MSc; VALENTINE, JO MSW, AND; ST. LOUIS, MICHAEL E. MD

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From the Epidemiology and Surveillance Branch, Division of STD Prevention, National Center for HIV, STD, and TB Prevention, Centers for Disease Control and Prevention, Atlanta, Georgia

Reprint requests: Lyn Finelli, DrPH, Epidemiology and Surveillance Branch, Mailstop E-02, Division of STD Prevention, Centers for Disease Control and Prevention, 1600 Clifton Road NE, Atlanta, GA 30333.

Received for publication February 23, 2000,

revised June 20, 2000, accepted July 12, 2000.

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Abstract

Background: Syphilis rates began to decline in 1991 and have decreased every year since. In 1998, 6,993 cases of primary and secondary syphilis were reported in the United States, for a national incidence of 2.6 cases per 100,000 population. Although syphilis rates are at an historic low, focal outbreaks still occur. On October 7, 1999, the Division of Sexually Transmitted Disease Prevention of the Centers for Disease Control and Prevention, in collaboration with federal and community partners, presented the National Plan for Elimination of Syphilis from the United States. One of the five key strategies of the plan is rapid outbreak response.

Methods: Methods for outbreak assessment and response were reviewed in the literature, synthesized, and adapted for use in syphilis outbreaks.

Results: Key elements of outbreak assessment and response are detection, surveillance data review, hypothesis generation, intervention development, and the evaluation of clinical, public health, and laboratory services.

Conclusions: Outbreak response necessitates community participation and a coordinated interdisciplinary effort to determine social and behavioral contributors to the outbreak and to develop targeted interventions.

FROM 1986 THROUGH 1990, an epidemic of syphilis occurred throughout the United States. 1 Syphilis rates began to decline in 1991 and have decreased every year since. In 1999, 6,657 cases of primary and secondary syphilis were reported in the United States, for a national rate of 2.5 cases per 100,000 population; both the number of reported cases and the rates of primary and secondary syphilis are lower in 1999 than ever before. 1 Syphilis in the United States is increasingly manifested as a disease characterized by sporadic epidemics rather than persistent endemicity, and although syphilis rates are at an historic low, focal outbreaks still occur. 2

On October 7, 1999, the Division of Sexually Transmitted Disease (STD) Prevention, National Center for HIV, STD, and TB Prevention, in collaboration with Health Resources Services Administration, Substance Abuse and Mental Health Services Administration, the National Institutes of Health, the National Institute of Justice, and partners in state and local health departments, community-based organizations, and researchers, presented the National Plan for Elimination of Syphilis from the United States. 3 The five key strategies of the plan focus on enhanced community involvement and partnerships at local, state, and national levels, enhanced surveillance, expanded access to quality health care for those infected or exposed to syphilis, improved health promotion, and rapid outbreak response. In conjunction with the National Plan, the Centers for Disease Control and Prevention has developed outbreak response guidelines for state and local health departments. There are several excellent articles and books 4–6 that address the mechanics of outbreak investigation and response; however, previously published guidance is more pertinent to outbreaks of diseases transmitted by food or the respiratory route than to sexually transmitted diseases. This article provides guidance specific to syphilis outbreaks and summarizes the Centers for Disease Control and Prevention outbreak response guidelines.

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Outbreak Detection and Threshold for Outbreak Response

Each jurisdiction with responsibility for outbreak detection and control must have a sensitive and valid surveillance system that will facilitate and inform outbreak detection. 7 There is no standard definition of a syphilis outbreak that is universally applicable. Instead, each health department should be familiar with the local epidemiology of syphilis and review their data on at least a quarterly basis to determine whether there are increases in the overall numbers of cases or shifts in the demography, local geography, or risk factors associated with syphilis in the community. 8 In areas of high syphilis morbidity where syphilis remains endemic, outbreak detection will be focused toward detecting focal outbreaks within areas of hyperendemic transmission. 9,10 In areas of low or no morbidity where syphilis has been eliminated or is largely controlled, outbreak detection will be focused toward the immediate identification of initial cases 11 and notification of the jurisdiction or country of origin. To prevent the reemergence of endemic syphilis in low-morbidity or no-morbidity areas, the nature and response of the health department to a case of syphilis should be similar in speed to a case of bacterial meningitis, botulism, or other communicable diseases for which an immediate response is mandatory. 3 All health departments serving low-morbidity areas should evaluate increases in specific racial, ethnic, or risk-behavior groups and determine whether observed increases warrant an outbreak response based on the changes in the demographic distribution of cases or on evidence that the outbreak is related to the emergence of risk behavior in specific groups. If an outbreak response is initiated, the state or local health department should assemble an outbreak response team. This team may be composed of disease intervention specialists, public health field workers, outreach workers, epidemiologists, clinicians, nurses, laboratorians, and behavioral scientists from the health department, community, and academic institutions. Composition of the outbreak response team will depend on the hypothesized reasons for the outbreak and the needs of the local area.

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Initiation of the Outbreak Response

The outbreak response team should arrange a meeting in the affected community with local public health officials, clinicians, and community leaders to discuss the purpose and scope of the outbreak and available resources. Other topics that may be addressed are political sensitivities pertaining to the outbreak response and persons responsible for communicating with the media and elected officials, if applicable.

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Confirm the Diagnosis and Review Clinical Data

A review of the clinical and laboratory data is necessary to make certain that case patients meet the syphilis case definition and are being classified to the appropriate stage of disease given the clinical and epidemiologic information. It is especially important to confirm the diagnosis in areas where syphilis has been eliminated. The diagnosis may be confirmed by reviewing the results of serologic tests and physical examination on a sample of case patients. Evaluating the distribution of stage of disease among case patients will provide information about the duration of the outbreak and whether cases are being detected soon after infection, when syphilis is most transmissible. Evaluating the distribution of case patients among healthcare providers and laboratories is also important because it will indicate where case patients are seeking health care. Finally, a determination of the proportion of case patients that are coinfected with gonorrhea, chlamydia, and HIV should be made to evaluate the possibility of intersecting epidemics.

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Review of the Case-Reporting System

A critical next step in the investigation is to evaluate the way that syphilis cases are reported to the health department and the information that is available from the analysis of those case reports. 12, 13 This evaluation should

* • Determine if there have been any changes in the surveillance case definition, 14 in the manner that the surveillance case definition is applied, or in the way that cases are ascertained; changes in surveillance practices can influence case detection and case reporting.

* • Evaluate the sources of case reports (e.g., laboratory, clinicians, health department staff, correctional institutions, hospitals, or STD clinics) and how case report data are stored (e.g., paper, morbidity cards, electronically).

* • Evaluate the type of information available for analysis from case reports and whether this information is complete and accurate.

* • Use the available case report data to plot the cases over time (epidemic curve). 15 Determine when the increase started and define this period as the outbreak period.

* • Compare the demographic and risk characteristics of case patients before the outbreak period with those who were identified during the outbreak period to evaluate whether the characteristics of syphilis case patients during both periods are similar or whether the outbreak is occurring in a new demographic or risk-behavior group. Make comparisons of case patients during the two periods for all stages of syphilis.

* • Evaluate the number of cases of congenital syphilis. Increases in the number of cases of congenital syphilis usually occur approximately 1 year after increases in syphilis among adults.

* • Create a spot map of cases that have occurred during the outbreak period and evaluate whether these case patients are geographically similar to preoutbreak case patients. 16 Pushpins on maps can be revealing, so a lack of access to high-tech software should not subvert this critical step. It might be useful to examine surrounding jurisdictions for concurrent increases in syphilis.

* • Inquire about the availability of other sources of surveillance data. Data regarding the prevalence of reactive syphilis serologic tests in populations that are routinely screened (i.e., prenatal clinics, drug treatment centers, emergency departments, or corrections facilities) might be useful because these screening data are independent of case reports, partner-notification activities, and other traditional methods of case detection. Other sources of surveillance data that are related to risk indicators for syphilis are data regarding emergency rooms visits for drug-related illness, the Arrestee Drug Abuse Monitoring program (ADAM), 17 and law enforcement data about arrests for prostitution or drug possession or distribution. Prevalence data can provide a snapshot of community syphilis morbidity and prevalence of risk behaviors related to syphilis and can inform the findings of the case report data analysis.

This careful analysis of the surveillance system and data should provide a picture of the data flow and will define the demographic and risk characteristics of case patients during the outbreak period. A social and behavioral assessment that can be conducted rapidly may also be useful in characterizing the syphilis outbreak. Furthermore, this kind of assessment often facilitates the involvement of affected communities in the development of the outbreak response by providing opportunities for members of affected communities and case patients to be interviewed about their perceptions of the outbreak, including potential contributing factors. Social and behavioral assessment may also offer STD programs significant opportunity to enlist intervention support and resources from other key health and social service partners as a result of engaging these external programs in the assessment effort.

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Evaluate Public Health, Clinical, and Laboratory Services

Options for STD clinical care should be assessed to determine if these services adequately meet the needs of the community, and it is important to consider whether both insured and uninsured persons have access to quality, confidential care. Contraction in the availability of STD clinical care may facilitate the transmission of adult syphilis. 18 Lack of prenatal care and missed opportunities for syphilis screening and treatment in pregnancy have resulted in congenital syphilis cases. 19 Moreover, an adequate number of experienced staff available for identifying cases and providing partner services are essential to controlling the outbreak. Persons with infectious syphilis should be treated as quickly as possible to reduce the opportunity for transmission, and the median amount of time that it takes from the date of the first reactive serologic test to treatment should be reviewed. Finally, the availability of quality laboratory services is extremely important. Laboratories should participate in a proficiency-testing program and should provide services that include darkfield microscopy or direct fluorescent antibody tests for Treponema pallidum for the diagnosis of genital ulcer specimens, and rapid plasma reagin screening. Rapid plasma reagin screening is essential for the expeditious treatment of persons affected by and contributing to the syphilis outbreak, especially those for whom reliable, timely follow-up visits may be difficult. Persons with genital ulcers and a nonreactive rapid plasma reagin in whom syphilis is suspected should be presumptively treated.

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Develop Hypotheses About Reasons for the Outbreak

When the outbreak has been confirmed and the epidemiologic data and public health, clinical, and laboratory services have been evaluated, data-informed hypotheses about the reasons for the outbreak need to be generated. Hypotheses are generated by reviewing the available epidemiologic and programmatic data and by interviewing case patients, healthcare providers, and members of the affected community. The epidemiologic data should be summarized and a risk profile of case patients developed. If a social and behavioral assessment was conducted, these data should also be summarized and used to highlight relevant social and behavioral factors contributing to the outbreak. In addition, programmatic data can be reviewed to determine if the increase in cases is associated with a breakdown in the public health infrastructure (e.g., clinic closure or reduction in public health staff). Sexually transmitted disease field workers could be brought together to explore the reasons for the outbreak and to identify commonalities among the case patients interviewed. A prioritized list of hypotheses about the reasons for the outbreak can be developed and discussed with key persons from the public health, clinical, and affected community. These activities conclude the outbreak assessment.

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Interventions

Given the hypotheses about the cause of the outbreak, a targeted intervention plan to interrupt the transmission of syphilis can be developed. 20 A discussion of the development of interventions is complex and beyond the scope of this article. In brief, a number of general activities can be beneficial to the intervention development and evaluation process. These activities most likely include enhanced surveillance, expanded clinical and laboratory services, and enhanced health promotion (Table 1). 3 It is recommended that an interdisciplinary team be convened to discuss the outbreak and intervention methods for the prevention and control of syphilis, including the prevention of congenital syphilis. Potential members of the interdisciplinary team could include public health officials, clinicians, members of the affected community, and relevant community leaders. It may also be advantageous to recruit participants from the state or local HIV community planning board as members of this team. Meetings with members of the affected community should be arranged to discuss the syphilis outbreak and the feasibility and acceptability of proposed interventions. One means of achieving this inclusion is to invite representatives from local community-based organizations to meet with the STD program members to discuss the outbreak and to collaboratively design strategies for intervention implementation.

Table 1
Table 1
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It is important that the specific syphilis control and prevention interventions developed in this partnership be piloted for feasibility and acceptability to the affected community members. Indeed, community involvement and new partnerships with other health and social service organizations may be essential. Additionally, programs will need to assess their respective capacities to sustain these intervention efforts to successfully respond to the outbreak. Finally, all intervention plans will need to be evaluated; ideally, the evaluation strategy should be developed before the intervention takes place.

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Discussion

The elimination of syphilis necessitates an urgent response to any increase in incidence in the community 3 and that each state and local STD program defines a community-specific threshold for outbreak response and an outbreak-response plan that is ready for implementation.

In 1937, the former Surgeon General of the United States, Thomas Parran, set forth principles for syphilis control that are relevant for syphilis elimination and outbreak response. Parran stated specifically that a

“teamwork of government, professions, industry and citizens” were necessary to eradicate syphilis, and that trained personnel for locating and treating case patients and educating the nation about syphilis prevention were the essential elements of syphilis control and eradication. 21 Parran also recognized that the control of syphilis is a complex activity. 21 Syphilis disproportionately affects some of the nation’s most disadvantaged communities that are besieged by poverty, unemployment, drug addiction, low rates of health insurance, and inadequate access to primary health care. Unlike persons involved in outbreaks of foodborne and respiratory diseases, persons with syphilis are often involved in high-risk activities such as illicit drug use, exchanging sex for money or drugs, unprotected anal intercourse, and having multiple sex partners. The most challenging part of outbreak response for syphilis can be defining the often anonymous sexual networks that facilitate transmission but that need to be defined to interrupt transmission. Many communities in which syphilis occurs have overburdened public health systems that must be strengthened so that outbreaks can be identified and addressed promptly and patients and their sex partners can be tested and treated appropriately.

Outbreak response is resource intensive and will necessitate that state and local STD programs engage in a collaborative effort to interrupt syphilis transmission. These STD programs can request assistance from other categorical programs within their health department. 22 Because some of the techniques used in general communicable disease outbreak control are relevant to syphilis, communicable disease program personnel are a valuable resource. If needed, fieldwork personnel can be garnered, from other disease control programs on a time-limited basis. State and city epidemiologists can also provide consultation, if not material assistance, in outbreak investigation and control. 22 Sexually transmitted disease programs will also need to collaborate with organizations outside their agency; community groups, community-based organizations, clinicians, and academicians.

Because syphilis elimination plans, including outbreak assessment and response, have only recently been developed and implemented in some jurisdictions with high morbidity, the methods of outbreak assessment and response described here have not yet been systematically evaluated. However, some evidence for their effectiveness exists. For example, the Florida Department of Health Bureau of STD Control has had an operational outbreak response plan and team in place since early 1999. The Bureau of STD Control initiated an outbreak response in Crescent City (population 2,000) when 28 cases of primary and secondary syphilis were reported between October 1998 and February 1999, compared with three cases for the same period the year before (D. George, unpublished data, 1999). The response included the deployment of 15 field staff from six surrounding jurisdictions to evaluate surveillance, quality of clinical services, and access to care, and to conduct enhanced case finding. The outbreak was largely among migrant farm workers and was associated with commercial sex. The outbreak team worked closely with local health care providers, businesses, city leaders, and the Migrant Farm Workers Association. Strategies used by the team to interrupt syphilis transmission were intensified partner elicitation and notification, widespread media coverage including distribution of printed health alerts, outreach screening, physician treatment of patients in field settings, and initiation of a jail screening program. The outbreak abated immediately after the intervention (D. George, unpublished data, 1999).

Effective syphilis outbreak assessment and response will necessitate collaboration between the public health and affected communities in the systematic collection and analysis of epidemiologic and behavioral data and in the development and evaluation of targeted interventions to interrupt syphilis transmission.

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References

1. Division of STD Prevention. Sexually Transmitted Disease Surveillance, 1999. US Department of Health and Human Services, Public Health Service. Atlanta: Centers for Disease Control and Prevention, October 2000.

2. Centers for Disease Control and Prevention. Primary and secondary syphilis—United States, 1998. MMWR Morb Mortal Wkly Rep 1999; 48: 873–878.

3. Division of STD Prevention. The national plan to eliminate syphilis from the United States. Atlanta: Centers for Disease Control and Prevention, October 1999.

4. Gregg MB, ed. Field Epidemiology. New York, NY: Oxford University Press, 1996.

5. Kelsey JL, Whittemore AS, Evans AS, Thompson WD. Methods in Observational Epidemiology. New York: Oxford University Press, 1996.

6. Teutsch SM, Churchill RE, eds. Principles and Practices of Public Health Surveillance. New York, NY: Oxford University Press; 1994.

7. Thacker SB. Historical development.In: Teutsch SM, Churchill RE, eds. Principles and Practices of Public Health Surveillance. New York, NY: Oxford University Press, 1994: 8–9.

8. Gregg MB. Conducting a field investigation.In: Gregg MB, ed. Field Epidemiology. New York, NY: Oxford University Press, 1996: 46–48.

9. Centers for Disease Control and Prevention. Outbreak of primary and secondary syphilis—Baltimore City, Maryland, 1995. MMWR Morb Mortal Wkly Rep 1996; 45: 166–169.

10. Centers for Disease Control and Prevention. Outbreak of primary and secondary syphilis—Guilford County, North Carolina, 1996–1997. MMWR Morb Mortal Wkly Rep 1998; 47: 1070–1073.

11. Centers for Disease Control and Prevention. Resurgent bacterial sexually transmitted disease in men who have sex with men: King County, Washington, 1997–1999. MMWR Morb Mortal Wkly Rep 1999; 48: 773–777.

12. Cates W, Williamson GD. Descriptive epidemiology: analyzing and interpreting surveillance data.In: Teutsch SM, Churchill RE, eds. Principles and Practices of Public Health Surveillance. New York, NY: Oxford University Press, 1994: 96–102.

13. Dicker RC. Analyzing and interpreting data.In: Gregg MB, ed. Field Epidemiology. New York, NY: Oxford University Press, 1996: 92–132.

14. Centers for Disease Control, Prevention. Case definitions for infectious conditions under public health surveillance. MMWR Morb Mortal Wkly Rep 1997; 46(RR-10): 34–37.

15. Goodman RA, Peavy JV. Describing epidemiologic data.In: Gregg MB, ed. Field Epidemiology. New York, NY: Oxford University Press, 1996: 60–80.

16. Cates W, Williamson GD. Descriptive epidemiology: analyzing and interpreting surveillance data.In: Teutsch SM, Churchill RE, eds. Principles and Practices of Public Health Surveillance. New York, NY: Oxford University Press, 1994: 126.

17. National Institute of Justice. 1998 Annual report on drug use among adult and juvenile arrestees (Arrestee Drug Abuse Monitoring Program–ADAM). United States Department of Justice. Washington: National Institute of Justice, April 1999.

18. Centers for Disease Control and Prevention. Impact of closure of a sexually transmitted disease clinic on public health surveillance of sexually transmitted diseases—Washington, D.C., 1995. MMWR Morb Mortal Wkly Rep 1998; 47: 1067–1069.

19. Centers for Disease Control and Prevention. Congenital syphilis—United States, 1998. MMWR Morb Mortal Wkly Rep 1999; 48: 757–761.

20. Goodman RA, Buehler JW, Koplan JP. Developing interventions.In: Gregg MB, ed. Field Epidemiology. New York, NY: Oxford University Press, 1996: 132–138.

21. Parran, T. Shadow on the Land: Syphilis. New York: American Social Hygiene Association, 1937: 243–267.

22. Finelli L, St. Louis ME, Gunn RA, Crissman CE, the Field Epidemiology Network for Sexually Transmitted Diseases. Epidemiologic support to state and local sexually transmitted disease control programs: perceived need and availability. Sex Transm Dis 1998; 25: 132–136.

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