Gerba questions the accuracy of such reports providing statistics of numbers infected by the parasite. They say there were only three cases in Phoenix last year. But, in reality, only six people may have been tested all year. The effects of crypto at this level are difficult to trace because of the diseases's rather lengthy incubation period of seven days. Few cases, therefore, are properly diagnosed.
Most infected people assume their nausea and diarrhea are from something they ate the day before.
The parasite comes from the feces of wild and domestic animals and is found in up to 87 percent of untreated water supplies. Rain runoff carries the parasite to surface water supplies. Gerba estimates that crypto is in about one third of the country's finished drinking water supplies. The parasite causes severe diarrhea and nausea. Phoenix and Mesa are testing for crypto even though it is not required.