BACKGROUND: The Centers for Disease Control and Prevention (CDC) has conducted national surveillance for waterborne disease outbreaks since 1971 in partnership with the Council of State and Territorial Epidemiologists and the United States Environmental Protection Agency (USEPA). Outbreaks were reported using a paper-based process until 2009, when CDC transitioned to the web-based National Outbreak Reporting System (NORS). Since the 1990’s, national waterborne disease outbreak data have been summarized in biennial reports, classified by type of water exposure implicated. Data on all waterborne disease outbreaks are not routinely summarized together.
METHODS: Public health officials in the 50 states, the District of Columbia, U.S. territories, and Freely Associated States voluntarily reported waterborne disease outbreaks to NORS and collaborated with CDC on a verification process for data on 2009–2014 outbreaks. The verification process follows the joint CDC—USEPA review of outbreak reports to clarify details necessary to finalize a national summary (note: 2013-2014 data are preliminary).
RESULTS: In total, 433 waterborne disease outbreaks with a first illness onset date occurring during 2009–2014 were assigned one of five water exposure categories: treated recreational water (n=200 [46%]), drinking water (n=110, 25%), untreated recreational water (n=61[14%]), other water (n=31 [7%]) or unknown water (n=31, 7%). These outbreaks resulted in at least 10,161 illnesses, 843 hospitalizations, and 76 deaths. Outbreak exposures occurred in 45 states and Puerto Rico. Most (n=242 [56%]) outbreaks started during June–August. Among outbreaks with a single confirmed etiology (n=344 [79%]), Legionella (n=138 [40%]), Cryptosporidium (n=98 [28%]), and Giardia (n=24 [7%]) were the most frequently identified pathogens; four outbreaks identified more than one etiology. Investigations of outbreaks with an unidentified etiology (n=85 [20%]) primarily implicated chemicals/toxins (n=39 [46%]) or bacteria (n=21 [25%]) as suspected etiologies.
CONCLUSIONS: NORS is a voluntary national reporting system used for reporting of all waterborne disease outbreaks to CDC. While data from NORS inform development of prevention and measures (e.g., health policy and communications) specific to individual water exposure categories, aggregate analyses can provide additional information to inform our overall understanding of the epidemiology and burden of waterborne disease in the United States. This abstract does not represent CDC or EPA policy.