CDC Legionella Surveillance Reports
Surveillance of Waterborne Disease Outbreaks Associated with Drinking Water — United States, 2015–2020
Access to and provision of safe water in the United States is critical to protecting public health (1). Disruptions to water service caused by drinking water contamination can negatively impact public health and erode public trust in drinking water quality. Each year in the United States, waterborne pathogens cause an estimated 7.15 million illnesses, 118,000 hospitalizations, and 6,630 deaths, resulting in $3.33 billion in direct health care costs (2). Drinking water exposures are associated with 40% of hospitalizations and 50% of deaths and are primarily linked with biofilm pathogens such as Legionella and nontuberculous mycobacteria (NTM), costing the United States $1.39 billion annually (3). Biofilms are microbial communities that attach to moist surfaces (e.g., water pipes) and provide protection and nutrients for many different types of pathogens, including Legionella and NTM (3,4). Biofilm can grow when water becomes stagnant or disinfectant residuals are depleted, resulting in pathogen growth (3). Furthermore, biofilm pathogens are difficult to control because of their resistance to water treatment processes (e.g., disinfection) (3). Exposure to biofilm pathogens can occur through contact with, ingestion of, or aerosol inhalation of contaminated water from different fixtures (e.g., showerheads) and devices (e.g., humidifiers) (3).
Public health surveillance and other prevention programs support water treatment, regulations, and building or household water management practices in reducing waterborne diseases. Public health agencies in the United States, District of Columbia, Federated States of Micronesia, Guam, Marshall Islands, Northern Mariana Islands, Palau, Puerto Rico, and U.S. Virgin Islands investigate and can voluntarily report waterborne disease outbreaks to CDC through the National Outbreak Reporting System (NORS) (https://www.cdc.gov/nors/about.html).
This report summarizes data on drinking water-associated outbreaks reported to NORS during 2015–2020. Drinking water, also called tap or potable water, includes water collected, treated, stored, or distributed in public and individual water systems or commercially bottled and distributed for individual use. Drinking water is used for consumption and other domestic uses (e.g., drinking, bathing, showering, handwashing, food preparation, dishwashing, and maintaining oral hygiene). This report summarizes outbreak contributing factors (i.e., practices and factors that lead to outbreaks) and, for the first time, categorizes outbreaks as biofilm pathogen or enteric illness associated (5–9). Public health departments, regulators, and drinking water partners can use the findings in this report to guide outbreak response and prevention programs and drinking water regulatory efforts.
