On March 1, 2013, the State A health department received a case report of primary syphilis (with chancre) occurring in a member of an American Indian Nation who resided on a reservation whose territory crosses State A and State B. This was the first case of early syphilis reported on this reservation in at least 20 years. By the end of July 2013, 5 additional cases of syphilis (including secondary cases with rash and asymptomatic latent cases) had been identified among persons residing on the State A side of the reservation. On September 12, 2013, State B reported its first case of syphilis on the State B side of the same reservation. Five weeks later, with 5 cases of syphilis in State B, State B notified State A of an increase in cases along the border, at which time each state learned of the other’s reported cases. On January 28, 2014, with 24 reported cases of syphilis on the reservation, including cases from both states, the tribe requested public health assistance from state and federal agencies to augment the ongoing public health investigation performed by State A and B health departments.

In February 2014, an enhanced, coordinated multiagency outbreak response began, involving the Tribal Health Agency, local and regional Indian Health Service (IHS) units, both State A and State B Departments of Health, and CDC; this included an onsite response from April 6 to 11, 2014, with technical assistance provided by partners through August 2015. A total of 136 cases of syphilis with onset from February 2013 to August 2015 were identified, including 2 cases of congenital syphilis that met the Council of State and Territorial Epidemiologists (CSTE) congenital syphilis case definition. Two additional cases of missed congenital syphilis (both stillbirths) were also identified. The stillbirth cases are considered “missed” because mothers were not tested for syphilis until 2 to 5 months after delivering a stillborn infant, at which time they were both found to be infected; fetal syphilis testing was not performed. These 2 missed cases do not meet the official CSTE congenital syphilis case definition and are not included in the outbreak case count.

A reported case of syphilis (any stage) was deemed outbreak-associated if it was diagnosed during February 2013–August 2015 in a person living on the reservation or in a person epidemiologically linked to a case from the reservation. Of the 136 outbreak-associated cases identified, 134 cases were among adults or adolescents, only 2 of whom identified as men who have sex with men. The outbreak was characterized as a primarily high-risk heterosexual outbreak with females representing more than half of all adult and adolescent (“adult”) cases (57%); of the 76 adult females, 13 (17%) were pregnant or had recently been pregnant at the time of their syphilis diagnosis. Adult cases ranged in age from 15 to 60 years and 99% of all cases were classified racially as American Indian/Alaska Native. One case was of unknown race. Adult cases represented all stages of disease, including 54 (40.3%) primary, 24 (17.9%) secondary, 42 (31.3%) early latent, and 14 (10.4%) late latent cases. Two congenital syphilis cases were identified and reported after the late detection and treatment of syphilis in their mothers (treatment initiated <30 days before delivery). Case reports peaked in April 2014 (n = 23), with a second, smaller peak in January 2015 (n = 6; Fig. 1.).

All 136 cases were identified through 1 of 8 case-finding activities: (1) first-trimester prenatal screening; (2) expanded third-trimester and day-of-delivery prenatal screening; (3) the implementation of electronic medical record (EMR) screening prompts in IHS facilities; (4) community screening events; (5) high-risk venue-based screening events; (6) collaborative interagency case-interviewing and partner services work, including clustering and social contact interviews; (7) testing of symptomatic patients; and (8) screening at non-IHS facilities. Other investigation and response activities included a review of state stillbirth records, which yielded no additional cases of congenital syphilis; community education activities to raise awareness of syphilis signs and symptoms among the general population; provider education activities to reeducate providers about syphilis testing and treatment; provision of field treatment for 18 persons who were either known cases or sexual partners of known cases with potentially incubating syphilis.

This heterosexual, reservation-based outbreak of syphilis, which included 134 adult cases and 2 congenital cases, was reduced in intensity as a result of an ongoing, coordinated set of case-finding and treatment activities. In the initial planning phase, the working group reviewed the outbreak-control literature for recommended syphilis outbreak interventions, but found that much of it was outdated or specific to commercial sex work and the crack cocaine epidemic of the 1990s.^11–25 Although we were informed by this literature, we primarily used the current outbreak epidemiology and local knowledge to craft the package of intervention activities used here. By presenting our results, we hope that others might be able to identify new syphilis outbreak control activities or better prioritize currently planned activities based on our documentation of efforts and case-finding results.

The single activity that identified the most cases was partner services and contact tracing, which led to the diagnosis of almost 40% of all outbreak cases. Although a high-yield activity from a case-finding perspective, partner services was one of the most labor-intensive components of this outbreak response, requiring daily effort from state DIS, IHS public health nurses, IHS infection control, and tribal community health representatives. Given the duration of the outbreak, it makes sense that a long-term activity like partner services, which was carried out over the entirety of the outbreak, contributed so greatly to case-finding relative to punctuated screening events in the community or at high-risk venues like the local jail. The novel enhanced partner services used in this outbreak, integrating federal, state, and tribal partners, may have played a role in finding more cases and bringing more persons to treatment than would have been found through traditional DIS-only partner services.

Other fruitful activities included symptomatic testing and the implementation of an EMR screening prompt. The volume of symptomatic testing in this population directly reflects the high levels of P&S syphilis seen during this outbreak. Nurse-led education sessions for the general reservation population as well as local media campaigns to raise awareness of syphilis signs and symptoms may have led to improved symptom identification and increased care seeking. The EMR prompt required initial programming by IHS staff but required little to no day-to-day oversight once implemented in the electronic record system. The workgroup assisted with provider training related to use of the prompt. After several weeks of screening with the prompt, IHS identified gaps in the system (i.e., not all positive RPR test results were automatically reflexing to T. pallidum particle agglutination testing) and worked quickly with their servicing laboratory to adjust the laboratory requisition.

Activities that attempted to screen a large number of people, both infected and uninfected, often required concentrated effort but for a significantly shorter period; the proportion of persons testing positive was relatively high at these punctuated events—with the initial jail screening finding that 5.2% of those screened were new cases of syphilis and the initial community event in a high-morbidity district finding that 6.3% of those screened were new cases of syphilis. The high prevalence of syphilis at these 2 events supports the idea that screening at venues frequented by high-risk individuals and targeted screening within high-morbidity communities may be valuable as one-time efforts. Although these efforts identified fewer cases (8/134 adult cases) than partner services, they also required less long-term commitment and were likely more valuable in slowing the spread of infection on the reservation by rapidly decreasing the number of infectious persons in the population. However, the reincarceration rates in this community were high enough that subsequent screenings at the same venue yielded diminishing returns.

Although significant energy was invested in provider education—passively through Health Alerts and actively through public health detailing with education messages—the expanded prenatal screening was not as high yield as the working group anticipated (finding only 1/134 adult cases of syphilis). That said, expanding screening to third trimester and day-of-delivery testing did contribute an additional 20% to case-finding efforts above and beyond the 5 cases detected through routine, first-visit prenatal screening. From a relative perspective, this may still be valuable, particularly if the primary goal is to prevent cases of congenital syphilis or to prevent long-term sequelae by identifying and treating infants known to be infected. Efforts to expand prenatal screening were somewhat hindered by the slow adoption of new recommendations at the individual provider level. Several instances were noted where providers refused to perform day-of-delivery testing despite receiving educational materials and Health Alerts asking them to do so. Although expanded prenatal screening did not produce significant case finding in and of itself, obstetricians did note (anecdotally) that they identified signs and symptoms of syphilis more readily after the educational sessions conducted by the working group. This may explain why an additional 3 pregnant women were categorized as “symptomatic testing” in the course of receiving prenatal care from an obstetrician. These women are not included in case counts of prenatal screening, because they had symptomatic infection during pregnancy (e.g., labial chancres) and are thus categorized as symptomatic testing.

Some of the challenges of syphilis outbreak control have already been noted, but a few others merit discussion. The unique context of the reservation—a remote geographic area in which multiple agencies serve in a public health capacity—creates a difficult environment for outbreak identification and response coordination. For similar outbreaks where multiple public health jurisdictions play a role in outbreak response, swift efforts to form interagency collaborations and undertake high-yield case-finding and treatment activities have been shown to speed outbreak containment.⁶ Our experience with an interagency working group also supports this notion, and we attribute much of our success in containing this outbreak to the coordination efforts of the IHS Regional Office and the willingness of all group members to communicate openly and act quickly. The challenges of outbreak identification and response were compounded here because the reservation spanned 2 states. This highlights the continued need for state and local health jurisdictions to establish agreements of understanding and work flows that allow communicable disease case and contact information to be shared when disease is identified near jurisdictional borders.

In this outbreak setting, it was initially unclear whether the state health departments had public health jurisdiction to investigate cases on the reservation. Although the states did have the jurisdiction to perform partner services work on reservation land, their presence on the reservation was alarming for tribal members, increasing reluctance and refusal among those needing to be interviewed, tested, or treated. After the problem was identified by the interagency working group, a hybrid model of enhanced partner services was established that involved the accompaniment of state investigators by community health representatives and public health nurses and the training of public health nurses in DIS-style interviewing to expedite partner services follow-up. This hybrid model was both culturally cognizant and effective, contributing to the location of additional cases and the willingness with which cases and partners agreed to testing and treatment. Community health representatives are well trained to perform community education around chronic disease and a variety of rapid diagnostic tests, but syphilis is a challenging disease, and extensive training would have been necessary for community health representatives to independently perform disease investigation on the reservation. For this reason, we feel that the hybrid model that included community health representatives, public health nurses, and fully trained state DIS was essential.

In small populations that are geographically isolated, heterosexual networks may be dense, which means that a disease introduced from outside has the ability to spread quickly. Congenital syphilis can emerge quickly if prenatal screening, rescreening, and treatment are not already in place. In this small reservation population, congenital syphilis emerged relatively quickly and was a large problem; although only 2 infants met the CSTE case definition for congenital syphilis, at least 2 other stillborn infants were likely “missed” cases of congenital syphilis. In a context where heterosexual syphilis seems to be emerging quickly and levels of prenatal care may be less than ideal, prevention of congenital syphilis through increased prenatal screening should be a high priority.

A coordinated multiagency response to a heterosexual syphilis outbreak on a US reservation, which included a series of case-finding and treatment activities, identified 136 cases of syphilis, including 2 cases of congenital syphilis. Although the case count on the reservation has not returned to zero (9 adult cases and 2 congenital cases were reported in 2016), transmission is believed to be relatively contained in large part due to the efforts of the response group, which were sustained by both health departments and the affected IHS service unit. Future heterosexual syphilis outbreak responders should act quickly to coordinate a package of high-yield case-finding and treatment activities—potentially including activities that seek to do the following: (1) increase prenatal screening, (2) improve community awareness and symptomatic test seeking, (3) educate providers and improve general screening for syphilis, (4) implement EMR reminders for providers, (5) screen high-morbidity communities and at high-risk venues, and (6) form novel partnerships to accomplish partner services work when the context does not allow for traditional, DIS-only partner services.