From MMWR in Review, Sept, 2018 by Drs. Su Jin Joo & Larry Pickering.
The most frequently reported infectious outbreak venues (32%) were pools, hot tubs and spas in hotels (i.e., hotels, motels, lodges or inns). Outbreaks increase in interactive water play venues in warmer months.
CDC recommendations
Chlorine is the primary barrier to transmission of most pathogens in recreational water. The Centers for Disease Control and Prevention (CDC) recommends chlorine concentrations of at least 1 part per million, which inactivates most pathogens within minutes (see table 2).
However, extremely chlorine-resistant Cryptosporidium can survive for more than seven days. Cryptosporidium is transmitted when a diarrheal incident occurs in the water, and the contaminated water is ingested. If an outbreak is suspected to be caused by Cryptosporidium, the CDC recommends hyperchlorination to achieve 3-log10 (99.9%) Cryptosporidium inactivation. Ultraviolet light or an ozone system can be added in venues at increased risk for contaminations (i.e., those intended for children younger than 5 years of age).
Legionella is transmitted by inhalation of aerosolized water droplets containing this bacterium, whereas Pseudomonas is transmitted when the skin comes in contact with contaminated water. Legionella and Pseudomonas are controlled effectively by halogens (e.g., chlorine and bromine) in well-maintained water venues. However, these pathogens can persist in biofilm, where microbial cells inhibit a primarily polysaccharide matrix, and the cells cannot be removed from a surface by gentle washing.
Effective water management programs for recreational venues at increased risk (hot tubs and spas) for Legionella growth and transmission can prevent outbreaks of Legionnaire’s disease. The state or local public health agency should be contacted to determine if laboratory tests are needed. CDC recommendations for disinfecting hot tubs/spas contaminated with Legionella are available at www.cdc.gov/legionella/downloads/hot-tub-disinfection.pdf.
Public health education
Preventing Cryptosporidium contamination is critical to preventing transmission. The key message to the public, especially to parents of young bathers, is “Don’t let your children swim if they have diarrhea.”
Preventing transmission of Legionella, Pseudomonas and other chlorine-susceptible pathogens means educating bathers and parents of young bathers to review the inspection scores of public recreational water venues and conduct their own mini-inspection before entering the water. Hot tub/spa users should be aware that they are at increased risk for Legionnaire’s disease.