BACKGROUND: In August of 2016, the Maricopa County Department of Public Health (MCDPH) investigated a cluster of cryptosporidiosis (crypto) cases with a common exposure to a high-volume recreational water venue. MCDPH, in collaboration with Maricopa County Environmental Services Department (MCESD), sought to define the scope of the outbreak and develop strategies to prevent further spread of disease.
METHODS: MCDPH interviewed laboratory-confirmed crypto cases using an outbreak-specific questionnaire that focused on identifying public recreational water facilities where cases had visited both before and after illness onset. Names of exposed facilities were provided to MCESD, which guided each identified facility through CDC recommended remediation processes to prevent additional illness. Healthcare providers were informed of the outbreak via a “Surveillance Alert" and the public was informed through the media with recommendations not to swim with diarrhea. Clinical specimens were tested by the Centers for Disease Control and Prevention (CDC) to determine the species and subtype and the relatedness of cases that visited different facilities.
RESULTS: From July 1 to December 7, 2016, MCDPH identified 440 confirmed and probable crypto cases based on the Council for State and Territorial Epidemiology case definition. Onset dates ranged from 7/1 to 12/7. The median age of cases was 12 (range <1 – 75) years. Fifty-two (20%) of interviewed cases were hospitalized; no deaths were associated with this outbreak. Seventy-five public recreational water facilities were identified from interviews and reported to MCESD. Few of these had secondary disinfection measures in place (e.g. ozone and/or UV) and required repeated remediation. CDC crypto hyperchlorination guidance changed without notification in July, complicating remediation efforts. One of four clinical samples submitted to CDC was identified as C. hominis species.
CONCLUSIONS: This is the largest crypto outbreak reported to date in Maricopa County. Due to the high volume of cases reported, prolonged swimming season and number of facilities affected county wide, a robust response from public health, environmental services, and aquatic facility managers was required. Challenges with the detection of cryptosporidium (in clinical and environmental samples), the absence of secondary disinfection measures at public aquatic facilities, and changes in remediation guidelines for facility operators contributed to the complexity of this investigation and response. This outbreak highlights the importance of rapid identification of exposed sites in a community-wide crypto outbreak to implement control measures and the critical roles of cross-departmental communication, data sharing, and timely notification and risk communication to the public.