University of Illinois Extension
Disaster Resources - University of Illinois Extension

Preventing Waterborne Illness

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In the aftermath floods, public health officials often monitor for waterborne illnesses, especially in communities where drinking and wastewater treatment plants were off-line for a period of time.

Waterborne illnesses caused by various bacteria, viruses and protozoa usually occur as a result of inadequately treated drinking and wastewater. Human symptoms for waterborne illnesses range from fever and malaise to the better known gastro- intestinal symptoms such as diarrhea and stomach aches.

At the time of the Midwest flood of 1993, floodwaters churned up a lot of debris from river bottoms and carried loads of organic and inorganic materials to the surface. Alternating turbulence and stagnation of river waters also created hospitable conditions for the growth and movement of many pathogenic (disease causing) microorganisms.

Most waterborne illnesses cause common symptoms. There is abdominal discomfort or cramping, fever, vomiting and diarrhea (characteristics of each depend on the pathogen). Loss of weight and fatigue may accompany several of the viral illnesses.

Normally, the human intestinal tracts contains many types of harmless bacteria that the body routinely eliminates. However when humans have prolonged exposures to the pathogens, such as in disaster situations or changes in personal hygiene habits, the pathogens can become opportunistic and cause illness. Generally, the incidence of waterborne illness in the United States is low compared to other major causes of illness. But when a natural disaster hits, waterborne agents can cause widespread illness and discomfort and in some cases, death.

The accompanying chart specifies more commonly experienced waterborne illness, the source of the infecting agent, where the agents are likely to be found in the water supply, and some general symptoms of each illness. If any of these symptoms persist, it is best to see a physician. Let the doctor know that your existing water system has been compromised due to a natural disaster, and advise the physician as to the source and type of water you are presently using. Since only 50 percent of waterborne disease agents are identified, you can increase the accuracy of your diagnosis if you can tell your doctor about changes in your drinking and bathing habits due to an interruption or change in your water service.

If your water supply was completely shut down during a natural disaster, the procedure for returning it to use varies depending on whether you receive water from a municipal supply or form a private source such as a well.

Municipal water

Before water services in your municipality can be turned back on, the Environmental Protection Agency or Health department in your state must inspect and sample the water to ensure it is safe to drink. The water must meet all Federal standards specified in the Safe Drinking Water Act, as well as any additional state requirements. Water-treatment operators must demonstrate that the water is properly disinfected and that a residual amount of disinfectant will remain in the drinking water once it is re-sent into consumers homes. State inspectors will also check water equipment such as pipes, storage tanks, mains and valves for breaks, cracks and failures before allowing the water system back on line. Repairs and replacements of any faulty equipment must occur before the community can once again receive a certifiably safe supply of drinking water.

Private wells

Private well owners can prevent waterborne illnesses by flushing out contaminated floodwater, disinfecting the casing of their wells, and re-flushing well systems before allowing the water to be used for household purposes again. Have the well tested immediately upon disinfecting and flushing and then follow up a week to two weeks later for re-testing. Usually a public health department will test wells for different types of pathogenic bacteria at no cost to homeowners, if they were affected by a natural disaster. Wells most likely to be vulnerable to bacterial contamination after flooding are shallow, have been dug or bored or have been submerged by flood water for long periods of time. Report any gastrointestinal or respiratory illness in family members to a physician or your local public health department; especially if it happens during well disinfection and start-up. If test results are negative or satisfactory from three or more samples taken two weeks apart, then well owners can safely proceed to reuse their water system.

Waterborne Diseases of Possible Concern When Flood Waters Recede
Disease and
Microbial Agent Sources of Agent
in Water Supply
General Symptoms
(Entamoeba histolytic)
(Cyst-like appearance
Sewage, non-treated drinking water, flies in water supply Abdominal discomfort, fatigue, weight loss, diarrhea, gas pains
(vibrio cholerae)
Untreated water, sewage, poor hygiene, crowded living conditions with inadequate sewage facilities Fever, abdominal pain, diarrhea
(of lesser concern in U.S.)
(vibrio cholerae)
Untreated water, sewage, poor hygiene, crowded living conditions with inadequate sewage facilities. Watery diarrhea, vomiting, occasional muscle cramps
(Cryptosporidium parvum)
Collects on water filters and membranes that cannot be disinfected, animal manure, seasonal runoff of water. Diarrhea, abdominal discomfort
(Giardia lamblia)
Most common intestinal parasite
Untreated water, poor disinfection, pipe breaks, leaks, groundwater contamination, campgrounds where humans and wildlife use same source of water. Beavers and muskrats act as a reservoir for Giardia. Diarrhea, abdominal discomfort, bloating, gas and gas pains
(Hepatitis A)
Raw sewage, untreated drinking water, poor hygiene, ingestion of shellfish from sewage-flooded beds Fever, chills, abdominal discomfort, jaundice, urine
(oral transmission)
(Salmonella species)
Contaminated water, shellfish, turtles, fish Gastroenteritis, fever and rapid blood-poisoning.
(Shigella species)
Sludge, untreated wastewater, groundwater contamination, poorly disinfected drinking water. Fever, diarrhea, bloody stools
Typhoid fever*
(of lesser concern in U.S.)
(Salmonella typhi)
Raw sewage (carried and excreted in feces by humans), water supplies with surface water source. Fever, headache, constipation, appetite loss, nausea, diarrhea, vomiting, abdominal rash
Legionnaire's disease*
(Legionellaceae and L. cincinnatus)
Cooling towers, showers through inhalation of vapors, raw sewage, stagnant clean drinking water in water tanks or towers, construction sites near rivers, lakes. Flu- and pneumonia-like symptoms: malaise, achiness, fever, chills, headache, nausea, dizziness, coughing, chest congestion, chest pain pressure, possible vomiting.
Pontiac fever
Same sources as Legionnaire's disease. Milder form of Legionnaire's disease. Pneumonia-like symptoms, but without fever. Illness is shorter in length.
Viral gastroenteritis
(includes Norwalk and rotavirus family)
Sewage, contaminated water, inadequately disinfected drinking water (mostly surface water sources). Repeated vomiting and diarrhea over 24-hour period, gastrointestinal discomfort, headache, fever.

* Physicians must report these illnesses to the Illinois Department of Public Health.

Issued by Mel Bromberg, University of Illinois Extension specialist, Water Quality/Health Issues. February 1995.

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