About Waterborne Disease Outbreaks


The purpose of this toolkit is to assist state and local health departments in conducting waterborne disease outbreak investigations.

Disease outbreaks that involve transmission through water can present unique challenges due to the numerous ways that individuals interact with it. To address these unique challenges, this toolkit describes similarities among many types of waterborne disease outbreak investigations based on best practices and experiences of epidemiologists at state and local health departments. This toolkit lays out a framework for a waterborne disease investigation and consolidates resources that may be useful to direct investigation activities.

Additional sections are available for specific situations that may require additional techniques, resources, or investigation activities.

Water-related Emergencies
Emergencies related to water (e.g., floods, droughts) can cause community-wide disruption and illness. Visit Emergency Planning, Training, and Response to find resources for the field before and after a WASH-related emergency.

About Waterborne Disease Outbreaks

Waterborne Disease & Outbreak Surveillance Reporting

  • Water contaminated with pathogens, chemicals, or toxins can lead to waterborne illness if you ingest it, inhale aerosols or gases from it, or it contacts your skin, eyes, ears, or other mucous membranes.
  •  A waterborne disease outbreak is defined as two1 or more people that are linked epidemiologically by time, location of exposure to water, and type of illness.
    • Epidemiologic evidence implicates water as the probable source of illness.
    • Environmental evidence can be important for implicating water as the source of infection (for example, water samples testing positive for pathogens).
  • Once a waterborne disease outbreak is detected, public health and regulatory officials work to collect data to identify a source of contamination and take action to prevent additional illnesses. Timely detection, response, and control of waterborne disease outbreaks is crucial for protecting public health.
    • Outbreak investigations can provide important data that may highlight safety gaps in water systems or identify strategies to reduce waterborne illness. The CDC is available to assist local, state, territorial, and tribal health departments and other countries’ ministries of health with investigating and controlling outbreaks.
  • Depending on the type of exposure and contaminant, waterborne pathogens can cause a variety of health problems, including gastrointestinal, respiratory, dermatological, and neurological illnesses.

1Case definitions vary between different pathogens or different contaminants. In some cases investigating an outbreak only requires 1 case.