An outbreak of E. coli infections has spread to three additional states—Pennsylvania, Illinois and Maryland—with seven more illnesses reported, according to CDC.

The outbreak, which has been linked to food served at Chipotle restaurants, now totals 52 illnesses across nine states. The most recent illness began on Nov. 13.

A majority of the illnesses were reported in the Pacific Northwest in early November. Of the 52 illnesses, 47 people reported eating at Chipotle in the week before getting sick. In response to the outbreak, Chipotle closed 43 restaurants in the Seattle, WA and Portland, OR earlier this month. These restaurants were later reopened after a thorough cleaning.

At this time, investigators say the evidence suggests a common meal item or ingredient served at Chipotle restaurants is likely the source of the outbreak. However, a specific source of the bacteria has yet to be found.

In a recent regulatory filing, Chipotle detailed just how much the outbreak has affected business with sales dropping by as much as 22 percent in the weeks following the announcement of the outbreak. Should these trends continue, the company says it thinks sales for the final three months of the year could be down 8 to 11 percent. Because of this, Chipotle says it can no longer reasonably estimate sales for 2016.

In light of the outbreak Chipotle says it has a renewed focus on food safety.

As a restaurant company, nothing is more important to us than serving our guests food that is delicious and safe to eat,” the company says. “Since this incident began, we have significantly increased our efforts to ensure that our teams are adhering to all of our food safety protocols, reassessed all facets of our food safety programs—from the farms that provide the ingredients we use, to the restaurants where we serve our customers—and made a number of improvements to help ensure that our food is as safe as it can be.”