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Wise Use of Antibiotics: Recreational Water Illnesses

Summer often brings opportunities to cool off in pools, lakes, rivers, oceans and water parks—activities enjoyed by children of all ages. However, recreational water exposure can also increase the risk of illness. Viruses, bacteria and parasites may be present in all types of water, including water treated with chlorine. Infection can occur through ingestion of contaminated water, inhalation of aerosols or direct contact with contaminated water.

An estimated 7.15 million waterborne illnesses occur annually in the United States.1 Among the most common are otitis externa, norovirus infection, giardiasis, cryptosporidiosis and campylobacteriosis.1 Children are disproportionately affected because they spend more time in the water and are more likely to swallow contaminated water. Understanding the presentations of recreational water illnesses can help clinicians recognize these infections, determine when diagnostic testing is warranted, and guide appropriate treatment.

Gastrointestinal Illnesses

Gastrointestinal infections are among the most frequently reported recreational water illnesses. Many pathogens are transmitted via fecal contamination of water sources, making a detailed exposure history particularly important when evaluating patients with summer-onset diarrhea or vomiting. Because the differential diagnosis is broad, not all patients will require stool testing. Most of these infections resolve spontaneously; even bacterial infections often resolve without antibiotics, and management generally relies on supportive care with hydration and electrolyte supplementation as needed. Two of the most common waterborne gastrointestinal infections are highlighted below:

  • Cryptosporidiosis

Cryptosporidiosis is one of the leading causes of waterborne disease outbreaks in the United States.2 It is caused by the protozoan parasites Cryptosporidium parvum and Cryptosporidium hominis, which are transmitted through the fecal–oral route. Infection may be asymptomatic or symptomatic, and ingestion of only a small number of oocysts can result in disease. Cryptosporidium oocysts are highly resistant to environmental conditions and many common disinfectants, including chlorine, allowing them to survive for extended periods in recreational water environments. As a result, outbreaks are frequently associated with swimming pools. The infection typically presents with self-limited watery diarrhea lasting several days.3 Most cases resolve without treatment within 10–14 days. Antiparasitic therapy with a three-day course of nitazoxanide is generally reserved for immunocompromised patients or those with severe illness and significant dehydration.

  • Giardiasis

Giardiasis is another common waterborne illness caused by the protozoan Giardia duodenalis.4 It is particularly prevalent among hikers and campers who consume untreated water from streams, rivers or lakes. Clinical manifestations include diarrhea, malaise, foul-smelling stools, abdominal cramps, bloating and flatulence. Although mild infections may resolve spontaneously, treatment is generally recommended to shorten symptom duration and reduce transmission. For children aged 3 years and older, tinidazole is preferred when available because it requires only a single dose.5 If tinidazole is unavailable, nitazoxanide administered for three days is an effective alternative. Nitazoxanide is also recommended for children between 1 and 3 years of age. For infants younger than 12 months, metronidazole administered for five days is the preferred treatment.

Skin and Wound Infections

Skin and soft tissue infections can develop when bacteria present in water or other wet environments enter through minor trauma or nonintact skin. The risk and spectrum of pathogens vary depending on the type of water exposure. In general, the risk of infection following aquatic exposure is highest in freshwater ponds and small lakes, is lower for brackish water and seawater, and lowest in treated water environments such as swimming pools and hot tubs.6 Obtaining a detailed history of water exposure and associated activities is essential when evaluating aquatic-related skin infections. Potential pathogens from freshwater include Aeromonas species, Edwardsiella tarda (often associated with catfish spine injuries), Mycobacterium species, Pseudomonas aeruginosa, and Streptococcus iniae (associated with handling fish).7 Vibrio species can be found in saltwater, although are rare in healthy children. Due to the broad array of gram-negative pathogens that can be involved in water-related skin and soft tissue infections, empiric use of a fluoroquinolone is more appropriate compared to cephalexin as in traditional skin infections. A frequently seen skin and soft tissue infection is highlighted below:

Hot tub folliculitis

Hot tub folliculitis typically develops within eight to 48 hours after exposure to inadequately maintained hot tubs or spas. Patients commonly present with pruritic or tender papules, papulopustules or nodules. Some individuals also report malaise and low-grade fever. The most common causative organism is Pseudomonas aeruginosa.8 Fortunately, the condition is usually self-limited and resolves without antimicrobial therapy. Supportive care is sufficient for most patients.

Ear, Eye and Respiratory Infections

Recreational water exposure can also contribute to infections involving the eyes, ears and respiratory tract. These illnesses may occur when contaminated water comes into prolonged contact with mucous membranes or when infectious particles are inhaled. Examples include viral conjunctivitis, often caused by adenovirus; otitis externa (swimmer’s ear); and Legionnaires’ disease. Although not infectious, exposure to aerosolized cyanotoxins produced during harmful algal blooms can also result in significant respiratory symptoms.9 The most common infection is detailed below:

Swimmer’s ear (otitis externa)

Otitis externa, commonly known as swimmer’s ear, is an infection of the external auditory canal. The condition develops when prolonged moisture in the ear canal disrupts the skin barrier, creating an environment conducive to bacterial growth. The most common causative organisms are Pseudomonas aeruginosa, Staphylococcus aureus and other gram-negative bacteria.10 Patients typically present with acute ear pain, pruritus, ear canal tenderness or a sensation of fullness in the affected ear. Topical antibiotic therapy, typically with fluoroquinolone-containing ear drops, remains the cornerstone of treatment.

Prevention

Preventing recreational water illnesses begins with minimizing fecal contamination of swimming and bathing areas. Public health recommendations include avoiding recreational water activities while experiencing diarrhea, showering before and after swimming, providing children with frequent bathroom breaks, and using swim diapers for infants, with diaper changes performed away from the water.

Individuals should also be encouraged to avoid swallowing recreational water whenever possible. These simple preventive measures can substantially reduce the transmission of waterborne pathogens and help ensure safer summer water activities for children and families. Local health departments can be valuable resources for evaluating local waterborne outbreaks.

References:

  1. Estimate of waterborne disease burden in the United States. Centers for Disease Control and Prevention. May 29, 2025. Accessed August 18, 2026. https://www.cdc.gov/healthy-water-data/waterborne-disease-in-us/results.html
  2. Cryptosporidiosis NNDSS summary report for 2022. Centers for Disease Control and Prevention. September 11, 2025. Accessed August 18, 2026.https://www.cdc.gov/healthy-water-data/documentation/cryptosporidiosis-nndss-summary-report-for-2022.html
  3. Leder K, Weller PF. Cryptosporidiosis: treatment and prevention. In: Connor RF, ed. UpToDate. UpToDate; 2026. Last updated June 5, 2026. Accessed August 18, 2026. https://www.uptodate.com/contents/cryptosporidiosis-treatment-and-prevention
  4. Minetti C, Chalmers RM, Beeching NJ, Probert C, Lamden K. Giardiasis. 2016;355:i5369. doi:10.1136/bmj.i5369
  5. Pasupuleti V, Escobedo AA, Deshpande A, Thota P, Roman Y, Hernandez AV. Efficacy of 5-nitroimidazoles for the treatment of giardiasis: a systematic review of randomized controlled trials. PLoS Negl Trop Dis. 2014;8(3):e2733. doi:10.1371/journal.pntd.0002733
  6. Diaz JH, Lopez FA. Skin, soft tissue and systemic bacterial infections following aquatic injuries and exposures. Am J Med Sci. 2015;349(3):269-275. doi:10.1097/MAJ.0000000000000366
  7. Diaz JH. Skin and soft tissue infections following marine injuries and exposures in travelers. J Travel Med. 2014;21(3):207-213. doi:10.1111/jtm.12115
  8. Spernovasilis N, Psichogiou M, Poulakou G. Skin manifestations of Pseudomonas aeruginosa Curr Opin Infect Dis. 2021;34(2):72-79. doi:10.1097/QCO.0000000000000717
  9. Clinical signs and symptoms caused by freshwater harmful algal blooms. Centers for Disease Control and Prevention. February 24, 2025. Accessed August 18, 2026. https://www.cdc.gov/harmful-algal-blooms/hcp/clinical-signs/symptoms-freshwater-harmful-algal-blooms.html
  10. Roland PS, Stroman DW. Microbiology of acute otitis externa. Laryngoscope. 2002;112(7 Pt 1):1166-1177. doi:10.1097/00005537-200207000-00005

 

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