Introduction | Waterborne Pathogens and the Diseases They Cause | Microbial Water Contamination and Human Exposure | Drinking Water Treatment | Improvements ... and What You Can Do
Less than 100 years ago, typhoid fever and amebiasis were the main causes of waterborne illnesses and deaths in the U.S. Thanks to contemporary water treatment measures, we have defeated old foes like typhoid fever, cholera, and dysentery.
But new threats have emerged in our waters. Microbial contamination of water is rare, but it can and does occur, causing illness and even death.
Some recent outbreaks have been caused by:
Probably the best known and most deadly case of contamination in the U.S. in recent years happened in Milwaukee in 1993, when the municipal water supply was contaminated by Cryptosporidium, an intestinal protozoan. At least 50 people died, and some 400,000 people became ill, 4,000 badly enough to be hospitalized.
Cryptosporidium image courtesy of Centers for Disease Control and Prevention (Parasite Library).
This deadly strain of intestinal bacterium killed seven people and made more than 1,000 others ill in Walkerton, Ontario, in 2000. Most likely, the town’s well water was contaminated when heavy rains washed manure into the wells at a time when the disinfection system was broken.
© Dennis Kunkel. Courtesy of Microbe Gallery.
In June 1998, hundreds of children were exposed to E. coli after playing in a water theme park near Atlanta. Two died and another 24 became ill.
Imported strawberries sickened about 150 students and teachers with hepatitis A in Michigan in 1997. This and similar outbreaks have been linked to produce grown outside the U.S. in countries with inadequate wastewater treatment that results in contaminated irrigation waters.
Hepatitis A. Courtesy of the Centers for Disease Control and Prevention.
This and other small, round-structured viruses cause outbreaks of gastrointestinal disease and are spread through contaminated water and food, often raw shellfish. Outbreaks in Florida, Louisiana, Maryland, Mississippi, and New York have been linked to the consumption of oysters.
Norwalk virus. Electron micrograph courtesy of B.V. Prasad, Baylor College of Medicine.
In the late 1990s, fish harvested in waters near the nation's capital were deemed unsafe for human consumption because of high numbers of this toxic alga.
Pfiesteria has been linked to serious neurological effects in humans and ulcerative disease in fish. Severe fish kills can result in millions of dead fish and lost dollars, like a 1997 outbreak in the Chesapeake Bay region that caused $43 million in economic losses.
Pfiesteria. Courtesy of Microbe Gallery.
In the summer of 2001, at least 69 people, many of them children, became ill with this intestinal bacterium, contracted from an inadequately disinfected wading pool in Atlanta, GA.
Shigella. © Dennis Kunkel.
It is impossible to determine how many cases of waterborne microbial infections occur in people each year because ailments can be misdiagnosed or easily go unreported. It can also be difficult to pinpoint the cause of an outbreak.
An estimated 2,038 Americans became ill from 17 outbreaks associated with drinking water during 1997–1998, according to the Centers for Disease Control and Prevention's most recent survey of water-related outbreaks. Infectious bacteria or protozoa were responsible for 10 of the outbreaks. Two were determined to have a chemical cause; the cause for the other five could not be determined with certainty.
During the same period, more than 2,000 people became ill from 32 outbreaks associated with recreational waters — beaches, lakes, and rivers. Most (29) were caused by infectious bacteria, viruses or protozoa. The cause of the other outbreaks could not be determined.
Introduction | Waterborne Pathogens and the Diseases They Cause | Microbial Water Contamination and Human Exposure | Drinking Water Treatment | Improvements ... and What You Can Do
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