1. General Discussion
One purpose of drinking water and wastewater treatment is to reduce the numbers of viable organisms to acceptable levels, and to remove or inactivate all pathogens capable of causing human disease. Despite the remarkable success of water treatment and sanitation programs in improving public health, sporadic cases and point-source outbreaks of waterborne diseases continue to occur. Water and wastewater may contain a wide variety of bacteria that cause intestinal or extra-intestinal infections. Waterborne pathogens enter human hosts through intact or compromised skin, inhalation, ingestion, aspiration, and direct contact with the mucous membranes of the eye, ear, nose, mouth, and genitals. This section provides an introduction to bacterial agents responsible for diseases transmitted by drinking and recreational waters in the United States.
The Centers for Disease Control and Prevention (CDC) and the US EPA maintain a collaborative system for collecting and reporting waterborne disease outbreak data for both microbial and chemical agents; however, detection and investigation of waterborne outbreaks is primarily the responsibility of the local, state, and territorial public health departments with voluntary reporting to the CDC.1 The average number of waterborne disease outbreaks per year between 1971 and 2013 was 46.2 From 1971 to 1998, 691 drinking-waterborne disease outbreaks due to a microbiological, chemical, or unknown etiology were reported in the United States (see Figure 9260:1). In the years 1972 through 1994, 291 outbreaks associated with drinking water were attributed to microorganisms as follows: Giardia lamblia, 109 (37.5% of total); Shigella, 34 (11.7%); nontyphoidal Salmonella serotypes, 13 (4.5%); Salmonella serotype Typhi, 5 (1.7%); Vibrio cholerae, 2 (0.7%), enterotoxigenic Escherichia coli, 1 (0.3%); E. coli O157, 1 (0.3%). Community waterborne outbreaks have declined since the mid-1980s (see Figure 9260:1), largely because of the promulgation of more stringent drinking water standards, including the Surface Water Treatment Rule,3 the Total Coliform Rule,4,5 and other regulations.6–8 In addition, many water utilities have made voluntary improvements.