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Waterborne Diseases

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Got Diarrhea? Poster from CDC

Waterborne Diseases

The Outbreak Response and Bioterrorism Investigation Team (ORBIT) investigates waterborne disease outbreaks associated with recreational water, drinking water, and environmental and undetermined exposures to water. Waterborne disease outbreaks are caused by many different microorganisms. In the United States, they include agents that cause intestinal, skin and respiratory diseases. Enteric pathogens, those that can cause nausea, vomiting and diarrhea, are most commonly associated with waterborne disease outbreaks. Some examples of waterborne pathogens that cause vomiting and/or diarrhea include: parasites (Cryptosporidium, Giardia), bacteria (Shigella) and viruses (norovirus). Skin infections can be caused by exposure to Pseudomonas and Schistosoma (Swimmer's Itch). Some respiratory diseases can be waterborne, such as Legionnaires' disease. For some waterborne disease outbreaks, the cause may not be determined. 

Waterborne diseases affecting people

Harmful Algal Blooms

Harmful algal blooms (HABs) are the rapid growth of algae that can cause harm to animals, people, or the local ecology. A HAB can look like foam, scum, or mats on the surface of water and can be different colors. HABs can produce toxins that have caused a variety of illnesses in people and animals. HABs can occur in warm fresh, marine, or brackish waters with abundant nutrients and are becoming more frequent with climate change. HABs have also been identified as sources of illness among persons and animals exposed to untreated recreational water. For the years 2009-2010, 11 HAB-associated outbreaks in the U.S. were reported to CDC’s Waterborne Disease and Outbreak Surveillance System (WBDOSS). Six of these HAB-associated outbreaks were in Ohio. If HAB outbreaks are identified, the local health department should notify the Ohio Department of Health's Bureau of Environmental Health & Radiation Protection Recreation Program or ORBIT for assistance.


Norovirus is a very contagious virus that causes vomiting and diarrhea. Anyone can get infected and sick with norovirus. You can get norovirus from:

  • Having direct contact with an infected person​
  • Consuming contaminated food or water
  • Touching contaminated surfaces then putting your unwashed hands in your mouth

This short video from the Centers for Disease Control and Prevention (CDC) explains what norovirus is, how it is spread, groups that are at high risk for severe disease and how you can protect yourself and loved ones from getting it.

Legionnaires' disease

Legionnaires' disease is caused by a bacterium known as Legionella. You can't catch legionnaires' disease from person-to-person contact. Instead, most people get Legionnaires’ disease when they breathe in mist (small droplets of water in the air) containing the bacteria. One example might be from breathing in droplets sprayed from a hot tub that has not been properly cleaned and disinfected. Outbreaks are most commonly associated with buildings or structures that have complex water systems, like hotels, hospitals, long-term care facilities, and cruise ships. Within these structures, the bacterium can become a health concern when it grows and spreads in human-made water systems, like hot tubs, cooling towers, hot water tanks, large plumbing systems, and decorative fountains. Most healthy people do not become infected with Legionella bacteria after exposure.