IN 1999, THE CENTERS FOR DISEASE Control and Prevention put forth a national plan to eliminate syphilis during a period of historic lows in cases of primary and secondary (P&S) syphilis.1 However, since that time, rates have steadily increased among men.2 Dramatic increases in syphilis cases have been reported in many large metropolitan areas, including San Francisco and Los Angeles, California; King County, Washington; Chicago, Illinois; Houston, Texas; Miami, Florida; and New York City, NY.3–8 This resurgence has been characterized by a large proportion of cases among men who have sex with men (MSM), high coinfectivity with HIV, and high-risk behaviors such as multiple partners and/or drug use. Although syphilis trends in these major urban areas are important to monitor because of high disease burden, they may not reflect trends in moderate- and low-prevalence areas. The epidemiology of syphilis in these areas may be unique, but this has not been adequately studied.
Knowing the epidemiology of syphilis in lower-prevalence areas is important for at least 2 reasons. First, understanding transmission patterns in these areas can provide insight into the overall dynamics of transmission at the national level. The core group hypothesis that a small group of cohesive individuals can sustain epidemic transmission of disease9 has been a useful construct in sexually transmitted disease research and has been empirically examined in many studies.9–11 Although no standard operational definition for a core group exists, the idea of a geospatial core, that is, a geographic area of high morbidity, has been proposed and examined.12 The degree to which areas of lower disease burden maintain their own core groups or import infections from external core groups is not known. Second, understanding the local epidemiology of syphilis transmission is necessary to implement region-specific prevention and control measures. The success of prevention strategies depends on appropriate design of control measures and effective resource allocation, which in turn depends on better understanding transmission patterns at the local level.
Connecticut is a relatively small northeastern state that covers 5,500 square miles and has approximately 3.5 million residents. Much of the state consists of suburban and other small towns. Urban areas include Stamford, Hartford, New Haven, and Bridgeport, which are relatively small (population range: 117,000–140,000) compared with the metropolitan areas mentioned previously (population range: 352,000–8 million), although Connecticut is located in close geographic proximity to the large urban areas of New York City and Boston, Massachusetts. The P&S syphilis rate in Connecticut in 2004 was 1.3 per 100,000 population, below the national average of 2.7 per 100,000 population, ranking it the 28th state.13 To address the lack of information about syphilis in low- to moderate-prevalence regions as well as to inform our local control strategies, this study examined the descriptive and spatial epidemiology of early syphilis in Connecticut in 2004.
Materials and Methods
Reporting of early syphilis (P&S and early latent) by providers and laboratories is mandated by law in Connecticut. Standardized case report forms provide information about age, sex, race/ethnicity, town of residence, and stage of infection. When the health department receives information about a case of early syphilis, field workers known as disease intervention specialists (DIS) contact the case to initiate a partner notification interview. This is the process by which DIS conduct in-depth, face-to-face interviews with patients to provide counseling and education and to obtain identifying and locating information about sex partners who should be notified of their potential exposure and the possible need for treatment.14 The DIS elicit information including, but not limited to, names and contact information for sex partners during the interview period (past 3 months for primary syphilis, past 6 months for secondary syphilis, past 12 months for early latent syphilis), total number of sex partners, meeting location and venues of sex partners, and self-reported HIV status. The interview is also used as an opportunity to educate patients about current trends in syphilis and provide risk-reduction counseling. Data for the present analyses came from surveillance reports to the health department and the field notes taken by DIS during partner notification interviews.
All case reports of early syphilis among men in 2004 were reviewed. Women were not included in this analysis because the number of cases (n = 6) was too small to provide meaningful results. To abstract relevant information for the present analyses, study staff met with the health department sexually transmitted disease control program regional supervisor to review syphilis case reports and field notes for 2004. All available cases were reviewed and relevant information contained in the field notes was verbally recounted to study staff, who recorded this information using one-page standardized abstraction forms. DIS who conducted the interviews were also consulted to provide additional detail as needed. All data used in this study existed before the start of research and no further contact with patients was necessary, and study staff did not obtain any identifiable information about any case or sex partner (e.g., name, description, or specific locating information). This study was exempt from review by the Yale University Institutional Review Board.
Descriptive statistics, including means, medians, and proportions, were estimated to describe the epidemiologic characteristics of syphilis cases. The number of cases by town was mapped using ArcGIS 9.1 software (Redlands, CA). To provide increased protection of confidentiality, no single town with a population less than 20,000 is reported as having a case of syphilis. For the 6 cases from towns with less than 20,000 population, the town of residence of the case was grouped with similar neighboring towns to achieve a group of towns with more than 20,000 population. Such regions are then referred to as “town areas” using the town name of geographic center of the area. Spatial analysis of cases was conducted using the global Moran's I test to examine possible clustering. This test statistic is analogous to Pearson correlation coefficient with values ranging from −1 to +1, and positive values indicating spatial autocorrelation (e.g., clusters or trends). To describe spatial patterns of sex partnerships, the town of residence of the case and the towns where cases reported meeting their sex partners were recorded for each reported partner. If patients did not give location information on sex partners that they mentioned, we considered that partner to be from the same town as the patient simply because no other location could be assumed. These data were visualized as a network of cities using Pajek software.15 The proportions of partners from the same city as the case, different city within Connecticut, and outside of Connecticut were computed. Because of the high proportion of partners reported from New York City, this was considered a separate category. The number of potential bridgers was estimated as the number of cases who had both in-state and out-of-state sex partners. The median distance between cases and partners was estimated using straight line distances obtained from a U.S. geological survey application (http://indo.com/distance). For instances in which sexual partners' location information was too general to calculate intercity distances (e.g., state or country only), we used the capital city of the region for the specific location used to calculate distance.
A total of 55 men were diagnosed with early syphilis in Connecticut in 2004 (see Table 1). Cases had an average age of 34.9 years (standard deviation: 11.1, range: 18–69 years). The majority of these cases (n = 32 [58%]) were diagnosed with secondary syphilis. Approximately 83% (n = 45) reported having had sex with at least one other man in the infectious period. Twelve cases (22%) reported knowing that they were HIV-positive. Six cases (12%) reported using drugs, including 5 reports of marijuana use and one report of methamphetamine use.
Cases were reported from 25 of 169 Connecticut towns (see Fig. 1). No town had more than 5 reported cases. Towns with the greatest number of cases (4–5 each) included Bridgeport, Hartford, New Britain, New Haven, Norwalk, and Stamford. The Moran's I test statistic revealed moderately significant spatial clustering of cases (P = 0.03).
The 52 syphilis cases for whom interview record data were available reported having a total of 197 partners during the infectious period, for an average of 3.8 partners per case and a median of 2 (see Table 2). Twenty-eight percent (n = 55) of these partners were named by patients during interviews such that the health department could initiate partner notification. DIS were able to locate 37 partners (19% of reported partners, 67% of named partners) and 29 partners (15% of reported partners, 53% of named partners) received treatment. Figure 2 displays the city network of sexual relationships between cases and their reported partners geographically according to meeting locations. Information about where the sex partner lived or where the sexual exposure took place was not available. Each node in the network represents a town or city, and the arrows represent cases naming partners. The sizes of the arrows are proportional to the number of partners named; the thinnest arrows represent one partnership, whereas the thickest arrow represents 24 partnerships. Nearly half of all partners (n = 95 [48%]) were from outside of Connecticut, with New York City being the most frequently mentioned out-of-state location (n = 55 [28%]). Within Connecticut, 74 partners (38%) were from the same city and 28 (14%) were from different cities than the case. Of the 52 cases, 26 (50%) reported partners from Connecticut only, 14 (27%) reported partners from outside of Connecticut only, and 12 (23%) reported having both in- and out-of-state sex partners. The median distance between the residence of the case and the location of the partner was 48 km (range: 0–4,178 km), equivalent to 30 miles.
The current epidemiology of early syphilis in Connecticut, an area of moderate prevalence, is similar to national trends with recent increases among men, the majority of whom are MSM (82%) and many of whom are also HIV-infected (22%). One notable difference, however, is in levels of reported drug use. Higher levels of drug use have been described in other syphilis reports (e.g., 40% in southern California3 and 36% in New York City6). The extent to which the lower level in Connecticut (12%) reflects differential underreporting or a real difference is not known.
Spatial patterns of cases and sex partners suggest that Connecticut is not a geospatial core area of transmission. First, the geographic dispersal of cases within the state is not consistent with the concept of a geospatial core group. The 55 cases came from 25 unique towns, and spatial analysis revealed only moderate clustering. Furthermore, nearly half of all sex partnerships were out-of-state, and the median distance between partners, 48 km, is substantially larger than distances reported in other studies of populations at risk for sexually transmitted infections (e.g., 339 m12 and 4.3 km16). Although our estimate is not directly comparable to these estimates because of the different study settings, it does provide a sense for the large distances between syphilis cases in Connecticut and their sex partners.
Reasons for nonlocal partners may reflect limited local opportunities to meet sex partners. Well-known and established venues that provide a social environment for MSM to meet are not readily available in Connecticut, presumably as a result of the “small town” nature of much of the state. For MSM with syphilis in Connecticut, sexual partner recruitment appears to rely heavily on travel to major urban centers. This, in turn, suggests that Connecticut is not a core or endemic area for syphilis transmission, but subject to substantial importation of disease.
Although it is likely that many syphilis cases in Connecticut are imported, the potential for transmission within the state exists if the individuals also have local sex partners. The proportion of potential bridgers in this study was 23%. This is substantially higher than the proportion of spatial bridgers for chlamydia and/or gonorrhea infection in King County, Washington, estimated to be approximately 5%.17 The relatively high number of potential syphilis bridgers indicates the need to monitor potential increases in local transmission, including transmission to the heterosexual community, and the establishment of new cores within the state.
Spatial characteristics of syphilis in Connecticut, namely diffusion within the state and high numbers of out-of-state partners, make preventive interventions difficult. Partner notification is logistically difficult, if not impossible, to conduct for distant partners. Furthermore, the dispersion of cases throughout the state makes targeted or venue-based efforts difficult. Additionally, social marketing campaigns that have been shown to increase syphilis testing18 might be difficult to develop, target, and manage in an acceptable manner in Connecticut.
Despite the challenges, the state health department in Connecticut has taken several steps to address the current increase in syphilis cases. First, efforts are underway to raise awareness among healthcare providers. Currently, health department staff are conducting one-on-one outreach visits with clinicians to inform them of importance of obtaining complete risk histories, including recent travel, and sex partner information from patients. Additionally, special efforts to raise awareness about the importance of screening are being conducted with HIV care providers. Second, the health department is partnering with a local community-based organization dedicated to gay and lesbian health issues to conduct outreach on popular web sites and in gay bars. Third, the DIS staff is implementing adaptive partner notification strategies in which they interview cases in pairs with anecdotal success in increasing the amount of partner information that is elicited. Finally, coordinated efforts between moderate- and high-prevalence areas located in close proximity remain important.
This study has some notable limitations. These findings may not be generalizable to other low- to moderate-prevalence areas of the United States, and such areas are encouraged to examine the local epidemiology of syphilis. Second, some patients did not give location information on all sex partners that they mentioned, perhaps to avoid health department involvement. We considered those partners to be from the same city as the patient, and this classification would underestimate the dispersion of sex partners. Finally, these data are subject to the limitations that apply to surveillance data such as dependence on a passive reporting system.
Despite these limitations, our findings are important because they present the first detailed look at the current epidemiology of syphilis in a nonurban, nonmajor metropolitan area of the United States. Other low- to moderate-prevalence areas in the United States may have similar patterns. Although the current epidemiology in Connecticut reflects the national pattern on a smaller scale, spatial characteristics such as the dispersal of cases and the likelihood of many imported infections need to be addressed in syphilis prevention and control efforts.
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