McDonald’s has stopped using fresh-cut onions and quarter-pound beef patties in several states, according to a statement from the fast-food giant. As of Tuesday, Wisconsin was not one of those states.

The first reported illness occurred about a month ago and the outbreak widely affected Colorado and surrounding states, but has spread as far west as Oregon and east to Wisconsin, according to the CDC. The reported death involved an older adult and occurred in Colorado, the agency said.

The CDC said it can take three to four weeks to determine if a sick person is part of an outbreak and that the number of people infected with the bacteria is likely higher than reported, as some people are treated for illness, but never testing for E. coli.