Note that the data published in the 2002 State of the Nation’s Ecosystems Report as well as the 2003 and 2005 Web-Only Updates have been superseded by the 2008 Report and thus should be used with caution. For the most recent data, purchase the 2008 Report from Island Press.

The Data

This indicator reports the number of waterborne disease outbreaks (WBDOs) reported to the Centers for Disease Control and Prevention (CDC) through a network of doctors and state and local public health officials. In addition, the U.S. Environmental Protection Agency (EPA) and the Council of State and Territorial Epidemiologists assist with collection and reporting of WBDOs. CDC generally reports only cases involving at least two individuals with a similar illness, and only where epidemiological evidence implicates water as the probable source of the illness. (Data from 1920 to 1936 include outbreaks that affected more than five people. These early data also include some cases related to contamination of reservoirs and cisterns, which are not included in the 1973–2002 dataset.) This indicator does not report outbreaks due to problems of unknown origin, nor does it include outbreaks caused by contamination of water or ice at the point of use (e.g., a contaminated water faucet). Outbreaks associated with recreational fresh surface waters are included here; outbreaks associated with marine water, spas, whirlpools, hot tubs, and the like are not reported.

Data Collection Methodology: State and territorial and local public health departments are primarily responsible for detecting and investigating WBDOs and voluntarily reporting them to CDC. CDC requests annual reports from state and territorial epidemiologists or from persons designated as WBDO surveillance coordinators. EPA collects additional information on water quality and treatment as needed from state drinking water agencies.

Data Manipulation: Information from CDC was sorted to identify only those outbreaks that are clearly linked to contamination in lakes, streams, ponds, and the like. Thus, outbreaks linked to contamination at the point of use and those linked to marine waters, hot tubs, spas, fountains, and swimming pools were omitted. Outbreaks associated with untreated and inadequately treated drinking water both counted toward the drinking water totals.

Data Quality/Caveats: Various factors can affect the chances of an individual illness being linked to a water source. These include public awareness, the likelihood that ill people will consult the same health care provider, availability and extent of laboratory testing, local requirements for reporting cases of particular diseases, and the surveillance and investigative activities of state and local health and environmental agencies. Recognition of WBDOs is also dependent on certain outbreak characteristics; large interstate outbreaks and outbreaks involving serious illness are more likely to receive the attention of health authorities. Outbreaks associated with private water systems that serve a small number of residences or farms are the most likely to be underreported because they generally involve only a few people.

Data Access: Current WBDO data are reported by CDC, Public Health Service, U.S. Department of Health and Human Services, in CDC Surveillance Summaries for Waterborne-Disease Outbreaks, Morbidity and Mortality Weekly Report. The 1985–2002 Surveillance Summaries are available at http://www.cdc.gov/mmwr/sursumpv.html; see Volumes 37, 39, 40, 42, 45, 47, 49, 51, and 53 . Data from 1978 to 1984 are from CDC’s Water- Related Disease Outbreaks Annual Summaries (1980–1985), and data from 1973 to 1977 are from CDC’s Foodborne and Waterborne Disease Outbreaks Annual Summaries (1974–1979).

2003 Web Site Update: Data for 1999 and 2000 were obtained from the CDC’s web site as listed in the Data Access section. Note that some inconsistencies were found in the data presented in the 2002 report, and these were corrected; these changes did not affect any general trends in the data.

2005 Web Site Update : Data for 2001 and 2002 were obtained from the CDC’s web site as listed in the Data Access section; these data included previously unreported incidents for 2000.