Syphilis Outbreaks Among Men Who Have Sex With Men

THE ARTICLE BY CHEN and colleagues, describing a syphilis outbreak in Los Angeles County that occurred during 1999 to 2000 among men who have sex with men (MSM), 1 is particularly timely and relevant; it provides an opportunity to highlight the nation's recent commitment to eliminating syphilis, address issues about how public health officials identify and contain syphilis outbreaks, and to highlight a worrisome public health trend that has important implications for syphilis elimination and HIV prevention. In October 1999, Surgeon General David Satcher announced the National Plan to Eliminate Syphilis from the United States. This commitment, supported by initiatives begun in 1988, was made to take advantage of the fact that in the late 1990s syphilis was at the lowest rate ever reported in the country and that the disease was concentrated in a small number of geographic areas. At the national level, syphilis elimination is defined as the absence of sustained transmission; at the local level, it is the absence of sustained transmission of new cases within 90 days of the report of an imported case. 2 The national goal is to reduce the annual number of primary and secondary syphilis cases to 1000 or fewer and to increase the number of syphilis-free counties from 78% in 1998 to 90% by 2005. 2 For this effort to succeed, establishment of partnerships with community organizations, public health professionals, the private medical community, and other partners working in the sexually transmitted disease (STD) and HIV fields is essential. Central to this effort is the need for local public health agencies, such as those in Los Angeles County, to promptly identify and contain syphilis outbreaks. Chen et al 1 appropriately emphasize that STD control programs must be prepared to respond promptly to syphilis outbreaks by having comprehensive plans developed and in place at the local level. However, their article does not highlight the equally important need to have—and the challenges of devising—suitable systems at the local and national levels to permit the rapid and reliable identification of outbreaks. A review of six STD programs found considerable variation in the thresholds used to detect syphilis outbreaks. Most programs use a predetermined increase in the rate of primary and secondary or early syphilis (usually a 20–30% increase in rates in comparison with previous months) to identify potential outbreaks. The approach used by the Los Angeles STD control program was somewhat more sophisticated and utilized the following criteria: (1) 5 epidemiologically linked syphilis cases identified within a 30-day period; (2) ≥3 cases or a 200% monthly increase in the number of reported syphilis cases in a high-risk group; or (3) a 200% increase (and >20 cases) in the number of syphilis cases reported in any health district in a month. 1 (Note that the response to the current outbreak was triggered by the second criterion). However, even this approach has its drawbacks, because information about sexual partners of infected MSM was limited by the anonymity of many of their sexual contacts; this may have prevented STD program staff members from initiating the outbreak response earlier on the basis of epidemiologically linked cases. Although tracking rates of disease on the basis of diagnosed cases is helpful for monitoring trends, it may not be a sensitive way to rapidly identify outbreaks because of the time required for investigation and reporting. To identify “best practices” regarding outbreak identification, epidemiologists should evaluate the performance of criteria that have been used to assess their “sensitivity” and “specificity.” But timely identification of syphilis outbreaks may require the development and use of innovative methods to detect variations in disease activity promptly without setting off too many false alarms. Approaches based on statistical process control methods may offer potential in this regard. 4 One such approach is a modified form of the cumulative sum (CuSum) method for detecting subtle differences between expected and observed values. Such methods were originally designed to allow factory workers to promptly detect subtle changes in quality of production output (i.e., “special cause variation”); modifications of these methods have been shown to be highly sensitive in detecting small increases in respiratory illnesses 5 and spontaneous abortions. 6 Routinely comparing the number of laboratory and/or case reports of syphilis to a predetermined baseline number of expected reports to assess patterns of variation from baseline may be a sensitive and methodologically consistent way to detect outbreaks in a timely fashion, and this method should be evaluated. The outbreak of syphilis among MSM in Los Angeles County 1,7 has not occurred in isolation and reflects a trend that is of particular concern. Similar such outbreaks have recently been identified in Chicago, New York, Boston, Miami, Seattle, and San Francisco. 8–13 The increase in syphilis among MSM is consistent with reports of increased high-risk sexual behavior among some MSM, 14 for which reasons may include “burnout” associated with safe-sex messages 15 or decreased concern about HIV infection acquisition or transmission, given the availability of highly active antiretroviral therapy. 16 The high incidence of syphilis among MSM is not a new phenomenon; rates of syphilis among MSM were high in the late 1970s and early 1980s. In fact, in 1982 in the United States, approximately 42% of males with primary and secondary syphilis named another male as a partner. 17 Rates of syphilis among MSM subsequently declined, reflecting demographic and behavioral changes associated with the AIDS epidemic. 14 The syphilis elimination efforts, as initially developed, 2 were targeted toward heterosexual minority populations and appear to be having some success. The rate of reported early syphilis (primary, secondary, and early latent syphilis) in the United States in 2000 was the lowest annual rate since reporting began in 1941; rates of primary and secondary syphilis and early latent syphilis were 2.2 and 3.5 cases per 100,000 persons. 18 Although the reported rate of primary and secondary syphilis among blacks (12.8 cases per 100,000 persons) in 2000 was 21 times greater than the rate reported for whites (0.6 case per 100,000 persons), it was more than 43 times greater in 1997; this substantial decrease in racial disparities reflects the greater rate of decline in the incidence of primary and secondary syphilis during the past 10 years among blacks than among any other racial or ethnic group. However, changes have recently been noted in overall male-to-female rate ratios for syphilis, which steadily increased from 1.1:1 in 1994 to 1.5:1 in 2000. The increase in the male-to-female rate ratios may be due in part to the increased rate of syphilis among MSM, as reflected by the outbreaks cited above. Clearly, syphilis elimination by 2005 will not be achievable if widespread resurgence of syphilis occurs among MSM. Because of shared behavioral factors and because STDs such as syphilis facilitate the transmission and acquisition of HIV, 19 increasing rates of STDs among MSM may foreshadow increasing rates of HIV infection among MSM. Chen et al found that approximately half of the 89 MSM identified with early syphilis were coinfected with HIV. 1 Among MSM in Seattle, 72% of those with syphilis whose HIV status was known were infected with HIV. 12 Although the recent outbreaks suggest that syphilis is reemerging among MSM, nationally reported syphilis data do not enable analysis of trends among MSM or other subpopulations because information on sexual behavior, sex partners, and risk factors for syphilis are not routinely collected or reported nationally. This limitation contributed to the delay in the identification of the increase in syphilis among heterosexuals during the late 1980s, 20 and it may have delayed identification of the recent outbreaks among both heterosexuals and MSM. To aid syphilis prevention and control efforts, information on behavioral factors, social determinants, and health-care-seeking practices should be consistently collected and available at the local and national levels. 21 Having data on the anatomical site of ulcers and the gender of sex partners would be particularly important. 22 Such information would permit closer monitoring of the evolving epidemiology of syphilis and would allow STD program administrators to develop outbreak thresholds for specific risk groups, including those, such as MSM, associated with specific behavioral practices. 23 The multifaceted response undertaken by the Los Angeles STD program, although a challenge to evaluate, appears to have contributed to a rapid decline in syphilis among MSM. However, after initial control of the outbreak as reported in the article, syphilis rates among MSM in Los Angeles increased to outbreak levels (unpublished data, STD Program, County of Los Angeles Department of Health Services). This may indicate that the underlying high-risk behaviors among the MSM community that permitted transmission of syphilis either never subsided or resumed after the intensive prevention effort; it may also indicate that some outbreak response activities need to be incorporated as components of the ongoing STD prevention program in that county. Qualitative data addressing underlying reasons for the behavior changes among MSM, delineating which MSM subgroups are at greatest risk, and identifying potential bridge populations could help in the development of appropriate prevention strategies. In response to national increases in syphilis and other STDs among MSM and because of implications for HIV transmission, the Centers for Disease Control and Prevention recently issued a public health alert 24 outlining action steps appropriate for national public health leaders, state and local health departments, HIV prevention community planning groups, community-based organizations, regional and national nongovernmental organizations, and the MSM community. A companion document to the National Plan to Eliminate Syphilis is being developed that outlines specific programmatic strategies to addressing syphilis among MSM. Such strategies include expanding partnerships to involve a broad variety of organizations concerned with MSM issues, actively encouraging providers to report cases of early syphilis and to include anatomical site of infection in these reports, and encouraging organizations that provide comprehensive services to MSM to include syphilis screening as a part of their routine services. Chen et al provide an excellent model for an outbreak response, much of which is appropriate for other STD programs. The effort to eliminate syphilis can be strengthened by the clearer delineation of which components are most effective and must be sustained and under what circumstances, as well as by the development of more sensitive methods for rapidly identifying outbreaks. However, the development and implementation of effective risk-reduction strategies that can and will be supported and maintained by MSM communities are critical.