E. coli bacteria linked to a cow-pasture party in Petersburg, Ill., has sickened more than 200 people, and the numbers are continuing to rise, health officials said. More than 1,800 people attended the Sept. 4 party. E. coli typically has an incubation period of three to eight days but can take longer. Officials have not pinpointed the source of the potentially fatal strain of E. coli, found in the feces and intestines of cattle. Twenty people have been hospitalized, but none of the reported illnesses was considered serious, said Thomas Schafer, a spokesman for the Illinois Department of Public Health.