Pathogenic Organisms

Microbial Contamination

The Commission remains concerned about microbial pollution in the Great Lakes basin ecosystem. While major problems occur infrequently, two relatively recent waterborne disease outbreaks in Wisconsin and Ontario make it clear that the potential for tragedy remains if drinking water is inadequately treated or challenged by high pollution loads. In 1993, an apparent failure in water treatment in Milwaukee, Wisconsin caused an estimated 400,000 cases of diarrheal disease and approximately 100 deaths, most caused by the Cryptosporidium parasite. Less than a decade later (2000), in the town of Walkerton, Ontario (located less than 100 km outside the basin), over 2,300 people were sickened and seven died after heavy rains compromised a municipal drinking water well and water treatment processes failed, leading to an outbreak of Escherichia coli (E. coli.) 0157 and Campylobacter jejuni bacteria.

Microbial infectious disease outbreaks demonstrate the fragility of barriers designed to protect public health. Research suggests these outbreaks are only a fraction of the actual number of gastrointestinal illnesses caused by microbial pollution each year.¹⁵ The U.S. Centers for Disease Control have reported increasing incidents of waterborne infectious disease in the United States, and it’s estimated that 6 to 40 percent of all gastrointestinal illness in the United States may be of waterborne origin. ¹⁶ Similar reports for Canada show that between 1974 and 1996, the last year for collected data, more than 200 reported outbreaks of infectious disease were associated with drinking water.¹⁷