Pseudomonas Dermatitis/Folliculitis Associated With Pools and Hot Tubs — Colorado and Maine, 1999-2000

Morbidity and Mortality Weekly Report, Dec 8, 2000

During 1999-2000, outbreaks of Pseudomonas aeruginosa dermatitis and otitis externa associated with swimming pool and hot tub use occurred in Colorado and Maine. This report summarizes these outbreaks and provides recommendations for swimming pool and hot tub operation and maintenance, particularly when using offsite monitoring of water disinfectant and pH levels or when cyanuric acid is added to pools as a chlorine stabilizer.

Colorado

In February 1999, the Colorado Department of Public Health and Environment (CDPHE) was notified of approximately 15 persons with folliculitis after they had used a hotel pool and hot tub. The cases occurred among children and adults attending two birthday parties at the hotel and among community residents who entered the pool on a pay-to-swim basis. The patients were treated for suspected Pseudomonas skin infections; one patient tested positive for Pseudomonas sp. by culture of a skin lesion.

Twenty-five community residents who used the pool and/or hot tub during February 5-7, were identified through discussions with area physicians, hotel management, and other swimmers. These community residents were interviewed by CDPHE using a telephone questionnaire. Case-patients were defined as persons who developed dermatitis/folliculitis, with or without other symptoms, within 3 days of using either the pool or hot tub at the hotel during February 5-7. Questionnaires were completed for 22 (88%) of the 25 persons identified. Of the 20 persons who used the hot tub, 19 developed a rash and met the case definition. Fourteen (74%) of the 19 case-patients had more severe illness (rash [greater than or equal to]2 weeks or rash and one other symptom) (Table 1), some lasting [greater than]6 weeks.

Specimens collected during the environmental inspection in May from the hot tub filter and hand rail base were positive for Pseudomonas aeruginosa and other Pseudomonas species. The pool and hot tub used separate filtration systems; each had an automated chlorination system that relied on an onsite probe to measure free chlorine and pH levels and deliver set levels of chlorine using calcium hypochlorite tablets and muriatic acid for pH control. A printout of the hourly free chlorine and pH levels in the pool and hot tub revealed that free chlorine levels dropped below state-required levels (1 mg/L) on the evening of February 4 and remained below recommended levels for approximately 69 hours. The decline in pool chlorine levels was the result of a faulty chlorine pellet dispenser. Hotel staff did not perform routine onsite water testing for the pool or hot tub.

Maine

The Maine Bureau of Health (MBOH) was notified of several cases of dermatitis/folliculitis among persons who had stayed at Hotel A in Bangor, Maine, during February 18-27, 2000. To characterize the illness and determine exposures associated with illness, MBOH conducted a case-control study among persons connected with a high school basketball tournament who stayed at hotels with swimming pools and/or hot tubs in Bangor during the outbreak. Case-patients had a rash for [less than or equal to]7 days or draining otitis externa with onset during February 18-March 3. Case-patients were matched by age and high school with healthy controls. Results from two (12.5%) schools were available for analysis. Nine persons were identified with rash, including one with otitis externa. Onset of symptoms occurred during February 20-March 1. Four of the nine persons were seen by a health-care provider. Case-patients ranged in age from 6-18 years (median age: 15 years); five were female (Table 2). The nine case-patients stayed a t hotel A and spent time in either the hot tub or pool; seven spent time in both. Case-patients were more likely than controls to have spent time in the hot tub (odds ratio [OR]=8.9; p=0.04) or to have used the pool (OR=7.4; p=0.06).

The indoor pool and hot tub were located within 5 feet of each other and had separate filtration systems. Pool disinfectant and pH levels were monitored by an offsite contractor. The pool had an automated chlorination system that relied on an onsite probe to measure chlorine and pH levels and to deliver a set level of chlorine using calcium hypochlorite tablets and muriatic acid for pH control. Chlorine and pH levels were maintained manually in the hot tub. To stabilize chlorine levels, 40-60 mg/L cyanurates were used. During the outbreak, free chlorine levels were tested daily and repeatedly registered [less than]1.0 mg/L, less than the state-required level of 1-3 mg/L, in the pool and hot tub. The pool and hot tub were crowded during the outbreak, and free chlorine levels were very low to zero after the February 25-26 weekend; no measurements were recorded over the weekend.

The facilities had been cleaned thoroughly before the environmental investigation in March. Pseudomonas aeruginosa was isolated from the top of the pool filter and from the draining ear of a child aged 6 years who used the pool. Although the pulsed field gel electrophoresis patterns of the two isolates did not match, the pool isolate was obtained after the facilities had been cleaned and may not have reflected the bacterial environment of the pool during the outbreak.