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Recreational waterborne illnesses threaten summer fun
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Research published in Environmental Health puts the annual number of recreational waterborne illnesses in the United States at about 90 million — costing an estimated $2.2 to $3.7 billion each year.
Susan C. Bleasdale, MD, medical director of infection prevention and antimicrobial stewardship at the University of Illinois Hospital and Health Sciences System, said in an interview that many children with diarrheal illnesses are not tested to determine the exact cause of disease, so many of these infections go unreported.
“A patient might come in with diarrheal illness and, oftentimes, you might not get additional testing, so you don’t get confirmation” Bleasdale told Infectious Diseases in Children.
Bleasdale said recreational waterborne illnesses should be considered if there are several cases occurring at the same time or if a whole family reports gastrointestinal symptoms. Then, physicians should start asking questions about recent vacations or if the patients frequent a particular pool.
“Patients don’t just walk in and say, ‘I have a waterborne illness.’ You have to figure out what their symptoms are, the time of year, and what might be the additional history you need to obtain,” she said.
The top five causes of recreational waterborne infection outbreaks, according to the CDC, are Cryptosporidium, Pseudomonas, Shigella, Legionella and norovirus. The most common cause — Cryptosporidium, or Crypto — was responsible for nearly 60% of all outbreaks associated with treated water with a known infectious cause from 2000 to 2014, according to an MMWR published last year.
Michele C. Hlavsa, RN, MPH, chief of the CDC’s Healthy Swimming Program and an author of the MMWR, told Infectious Diseases in Children that the Crypto parasite can be difficult to control because it can tolerate chlorine.
“Chlorine at levels recommended by the CDC for pools or water playgrounds kills most germs within minutes,” she said. “Cryptosporidium can survive for 7 or more days.”
Cryptosporidiosis is usually self-limited and resolves well in most patients, but those with weaker immune systems may develop much more severe illness, according to Bleasdale.
Hlavsa said that the CDC will be releasing a report later this summer that focuses on Crypto outbreaks, many of which are linked to swimming, contact with cattle and child care settings.
The 2018 MMWR also showed that hotel pools are a frequent source of recreational waterborne disease, causing 32% of all swimming-related disease outbreaks in the U.S., but these infectious pathogens can be transmitted in a variety of other settings — including water parks, beaches and lakes.
Infection prevention
The CDC recommends several strategies to prevent recreational waterborne diseases through their Healthy Swimming Program. Hlavsa said one of the organization’s most important recommendations is that children should avoid swimming when sick with diarrhea until after symptoms have completely cleared.
“If a child has diarrhea and they are diagnosed with cryptosporidiosis, we advise pediatricians to tell parents not to take the child swimming,” she said. “This is true not only while the child is sick with diarrhea but until the child is at least 2 weeks diarrhea- or symptom-free.”
She said this is because people can continue shedding the parasite in stool after symptoms have resolved. Bleasdale suggested that physicians should remind families to wash their hands, especially after using the restroom and changing diapers.
Some tips to prevent recreational waterborne illnesses apply to both natural and manmade water sources — including not swallowing the water. However, Bleasdale said special precautions need to be considered when swimming, diving, kayaking, rafting and fishing in fresh water.
“In general, for freshwater swimming, you want to make sure you’re plugging your nose and closing your eyes,” she suggested. “If you are kayaking, rafting or participating in similar activities, you want to make sure that you’re wearing shoes so you don’t get any abrasions or cuts and get water from that venue into the wound. You also want to avoid water that’s potentially contaminated with stool from people or animals to decrease your risk.”
The CDC recommends checking the water quality results for beaches and other sites through the Environmental Protection Agency before swimming. Families can check the inspection scores of public pools, hot tubs and other manmade sources of water before swimming, or water can be tested for pH and chlorine levels using test strips. National recommendations suggest that a pool’s pH should be between 7.2 and 7.8, and free chlorine concentrations should be at least 1 ppm. If a Crypto outbreak is occurring in the community, health departments may request that pools hyperchlorinate, which includes closing the pool to the public, using unstabilized chlorine to maintain a pH of 7.5 or less, and raising the free chlorine concentration to at least 20 ppm for 28 hours. Higher levels of chlorine can be used for shorter periods of time.
“Swimming is a great way to be active with your friends and family,” Hlavsa said. “We need to make sure we are swimming healthy and being smart about it. We put our seatbelts on before we go off somewhere in our cars. This is just about making healthy choices before you swim, testing the pool water or water playground, not swimming with diarrhea, not drinking the water we swim in and checking inspection scores. It’s all about minimizing risk and having a great time.” – by Katherine Bortz
- References:
- CDC. Healthy water. https://www.cdc.gov/healthywater. Accessed May 20, 2019.
- CDC. Disinfection & Testing. https://www.cdc.gov/healthywater/swimming/residential/disinfection-testing.html. Accessed May 20, 2019.
- CDC: Healthy Swimming - Hyperchlorination to kill Cryptosporidium when chlorine stabilizer is in water. https://www.cdc.gov/healthywater/swimming/pdf/hyperchlorination-to-kill-crypto-when-chlorine-stabilizer-is-in-the-water.pdf. Accessed May 28, 2019.
- CDC. Healthy Swimming - Oceans, lakes and rivers. https://www.cdc.gov/healthywater/swimming/oceans-lakes-rivers/index.html. Accessed May 20, 2019.
- CDC. Waterborne disease & outbreak surveillance reporting - National Outbreak Reporting System. https://www.cdc.gov/healthywater/surveillance/nors.html. Accessed May 20, 2019.
- CDC. Waterborne disease & outbreak surveillance reporting - Waterborne disease & outbreak surveillance. https://www.cdc.gov/healthywater/surveillance/index.html. Accessed May 20, 2019.
- DeFlorio-Barker S, et al. Environ Health. 2018;doi:10.1186/s12940-017-0347-9.
- Hlavsa MC, et al. MMWR Morb Mortal Wkly Rep. 2018;doi:10.15585/mmwr.mm6719a3_w.
- For more information:
- Susan C. Bleasdale, MD, can be reached at sparmet@uic.edu.
- Michele C. Hlavsa, RN, MPH, can be reached at acz3@cdc.gov.
Disclosures: Bleasdale and Hlavsa report no relevant financial disclosures.