Pseudomonas Infection Outbreak Associated with a Hotel Swimming Pool — Maine, March 2023

Investigation and Results

Reports of Illnesses Associated with Hotel A Swimming Pool

On March 7, 2023, the Maine Center for Disease Control and Prevention (Maine CDC) received a report from a group of hotel guests who had developed ear pain, rashes, and eye irritation after using a swimming pool at hotel A during the March 4–5 weekend. Later that day, an additional family that had used hotel A’s swimming pool the same weekend reported experiencing similar illness, in addition to redness and pain of their hands and feet. Over the next 2 days, four additional groups of guests reported similar illnesses after using the hotel A pool during the same weekend. On March 7, in response to the reports, Maine CDC’s Health Inspection Program contacted hotel A and learned that management had voluntarily closed the pool after receiving guest complaints. In response, on March 8, Maine CDC initiated an epidemiologic, laboratory, and environmental health investigation.

Case Identification

Maine CDC used illness reports to identify six households with members who had visited hotel A’s pool during the weekend of March 4–5 and interviewed a representative from each household using a standard questionnaire. Interviewers asked about other groups or persons who had used the hotel pool; additional identified persons were also contacted and interviewed. Guests were asked about their use of the hotel A pool, other pools, and hot tubs since February 24, and subsequent illness.

A total of 10 households (30 guests) were identified as having visited or used the hotel A pool during March 4–5 (Figure 1); one person per household was interviewed about all household members who used the pool. To further assess the scope of the outbreak, Maine CDC obtained a list of registered guests who were at hotel A during March 1–7 and identified 29 additional registrants who might have been present at hotel A during March 4–5. These additional registrants were sent the standardized questionnaire by text or email and asked to fill out a separate questionnaire for each household member who used the pool. Questionnaires were completed for five additional guests.

A total of 15 interviews or questionnaires were completed for 35 unique persons. Maine CDC requested that symptomatic guests ask their health care provider to obtain a skin lesion swab for laboratory analysis and requested that laboratories send any isolates to Maine’s Health and Environmental Testing Laboratory. This study was reviewed by CDC, deemed not research, and was conducted consistent with applicable federal law and CDC policy.*

A case was defined as the occurrence of ear pain, rash, or pain or swelling in feet or hands in a person within 7 days after using the hotel pool during March 4–5. Among 35 persons for whom information was available, 26 (74%) reportedly used the hotel A swimming pool during March 4–5. Among these 26 persons, 23 (88%) experienced an illness meeting the case definition; illness onset date was available for 20 persons (Figure 2). Among the 23 patients, 16 (70%) had ear pain, 15 (65%) had a rash, and seven (30%) had pain or swelling in their feet or hands (Table). Fifteen (65%) patients were female. Among 22 patients with available information, age ranged from 5 months to 61 years (median = 8 years). Among 20 patients with reported time and date of illness onset, illness began a median of 24 hours (range = 8 hours–6 days) after use of the hotel A pool.

Laboratory Evaluation

Skin lesion swabs were obtained from three patients, two of whom were family members who lived in separate households, spent time together outside of the hotel pool, and had no other pool or hot tub exposures. P. aeruginosa was identified in all three specimens; the isolates of the two family members were sent to Maine’s Health and Environmental Testing Laboratory for whole genome sequencing. Single nucleotide polymorphism (SNP) analysis, using CLC-BIO (version 23.0.2; Qiagen Aarhus), indicated that the two isolates were highly related with a two-SNP difference, suggesting a common exposure.

Hotel A Pool Inspections

In January 2022, the hotel pool had failed a routine health department inspection. During that inspection, several violations were identified: 1) no operator had successfully completed approved training, 2) no pool logs documenting free chlorine^† concentration readings at least three times per day while the pool was open for use, 3) no posted routine operating procedures, and 4) no functioning disinfectant feeder installed. During the subsequent March 8, 2023, inspection, the health inspector noted that although the hotel did have an operator who had successfully completed approved training <2 weeks before inspection, none of the other previously identified violations had been corrected. The pool logs for March 1–5 showed two compliant free chlorine concentration readings, not the expected 15, and both readings were dated March 3. The inspector also noted that an indeterminant amount of chlorine had been added to the pool water by hotel staff members after they voluntarily closed the pool; therefore, water quality and environmental samples were not collected.

Because the identified violations included imminent health hazards and uncorrected previously identified violations, Maine CDC’s Health Inspection Program directed hotel A to not reopen the pool until all the violations were addressed. The health inspector provided recommendations to address the violations. On reinspection 1 month later, the violations were noted to be corrected. No additional hotel A pool-associated illnesses were identified after reopening.