Manure has been blamed for much of the bacteria and viruses that pollute Wisconsin drinking water, but contamination from human waste is a problem, too.
Failing septic systems, leaking public sewer pipes and landspreading of septic waste can introduce dangerous pathogens into both rural and urban water systems.
In June 2007, 229 people were sickened by a norovirus in Door County while eating at a restaurant. Seven were hospitalized as a result of the pathogen, which is known for spreading illness on cruise ships. The source: a leaky septic system.