In 2020, a Centers for Disease Control and Prevention (CDC) study estimated that waterborne illnesses affect around 7.2 million Americans annually, posing a public health concern. They can spread through drinking water, recreational bodies of water like swimming pools and lakes, and via water used for agriculture, and manufacturing.
Waterborne illnesses are diseases caused by pathogens — bacteria, viruses, and parasites — that travel via water and are contracted by drinking or encountering contaminated water.
Per CDC estimates, the five most common waterborne illnesses in the US are:
The CDC estimates that 6,630 people die annually from waterborne illnesses. The waterborne illness estimated to cause the highest number of deaths is nontuberculous mycobacterial (NTM) infection, followed by Legionnaires’ disease, pseudomonas pneumonia, pseudomonas septicemia, and otitis externa or "swimmer’s ear."
Along with deaths, these illnesses are also estimated to lead to the most hospitalizations. NTM infections are estimated to cause the most fatalities and hospitalizations.
Consistent water quality violations along with aging infrastructure mean households nationwide continue to face contaminants in drinking water.
Recreational water illnesses are spread by swallowing, inhaling or having contact with contaminated water in swimming pools, hot tubs, water parks, water play areas, interactive fountains, lakes, rivers, or oceans.
According to the CDC’s National Outbreak Reporting System, recreational water illnesses were responsible for 50% or more of reported waterborne illnesses from 1995 to 2021, except for 2017, 2019, and 2020.
Recreational water can be contaminated with pathogens and chemicals that cause various illnesses, including gastrointestinal, skin, ear, respiratory, eye, neurologic, and wound infections. Some common pathogens found in recreational water include:
“Hot tub rash,” also caused by pools and lakes, results from contaminated water that stays on skin for an extended time. The germ that causes contamination is called Pseudomonas aeruginosa and originates in water that is not properly disinfected with chlorine or falls outside of the recommended pH level of 7.2–8.
Shingella germs come from fecal matter such as diarrhea and is spread by swimming in, or swallowing, contaminated water. It can also be spread by encountering fecal matter in other ways, such as through changing diapers, sexual contact, or eating food prepared by someone who has a Shingella infection.
The CDC recommends that individuals prevent waterborne illnesses at home, and while camping, hiking, and traveling, and backpacking by practicing safe measures like keeping water infrastructure maintained and treating and purifying water correctly. Waterborne illnesses can be prevented at industrial and commercial levels by implementing safety standards.
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Estimates are not actual values. For each waterborne illness in the study, reported illness data was corrected for underdiagnosis and underreporting. The data was adjusted to account for domestic cases only. To calculate deaths, the study applied an uncertainty model to generate a 95% credible interval with upper and lower limits centered around a point estimate. The full study methodology is here.
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