Introduction to Waterborne Pathogens

Yates, M.V.

Every year, dozens of waterborne disease outbreak occur in the United States. Statistics on the outbreaks associated with dringing water and recreational water are compiled and analyzed for the Centers for Disease Control and Prevention. This information is published biannually in the Morbidity and Mortality Weekly Reports Surveillance Summaries ( There are hundreds of different pathogens that can be transmitted by exposure to contaminated water. Many of these pathogens are enteric in nature, meaning that their primary site of infection is the intestines. Exposure to enteric pathogens is typically through consumption of food or water that contains the pathogens. In the body, the pathogen typically infects the gastrointestinal tract, the result of which is generally gastroenteritis, which has symptoms of nausea, vomiting, diarrhea, and/or fever. Some of the enteric pathogens infect other organs, such as the liver (e.g., hepatitis A virus) or nervous system (e.g., poliovirus), and thus cause more severe illnesses such as hepatitis and poliomyelitis. Infection by some enteric organisms has led to non-enteric sequelae. For example, Campylobacter infections may lead to development of Guillain-Barré syndrome, which is the most common cause of acute flaccid paralysis (a symptom of which is extreme weakness in the legs) in the United States (Nachamkin, 2002). Another example is the production of reactive arthritis, in which the body’s immune system reacts to certain bacterial infections by producing inflammation of the joints; this has been seen following infections by Campylobacter, Salmonellae, and Shigellae (Moe, 2002). Other pathogens, are transmitted through other routes. For example, Pseudomonas infections can be acquired through contact with the skin, leading to dermatitis. Legionella infections result from respiratory exposure. Because there are hundreds of different pathogens that could be present in water, it is generally not economically, technologically, or practically possible to test water to determine whether it contains pathogens. Therefore the approach has been to use one microorganism (or group of microorganisms) to indicate whether or not a health risk exists. Different bacterial groups have been used as indicators of the microbiological quality of drinking water, and recreational waters for many years. For example, total coliform bacteria have been used for decades to assess the microbiological quality of drinking water. Clearly, there are a number of issues to consider and choices to make when establishing a program to monitor the microbiological quality of water. The purpose for which the monitoring is being conducted will dictate some of those choices, but consideration of available resources and personnel are also important. No one indicator or pathogen can provide all of the information that may be desired, and there are limitations associated with any choice that is made. Therefore, it is important to spend time carefully planning the project, by gathering the available information and seeking the advice of experts, before beginning any monitoring program.