SPRINGFIELD, Ill. — Health officials in Illinois and Iowa are investigating an increase in people becoming sick from a parasite that causes intestinal illness.

The Illinois Department of Public Health said in a news release Thursday that it has received confirmation of about 90 cases of cyclosporiasis, which is caused by the Cyclospora parasite. The Iowa Department of Public Health, in its own release, said it has identified 15 cases linked to the same illness and parasite.

Both departments say there appears to be a link to consumption of McDonald’s salads. The departments say McDonald’s is also investigating and has been fully cooperating with state health officials, the Centers for Disease Control and Prevention, and the Food and Drug Administration.

The Illinois cases date back to mid-May and the Iowa ones to late June.

People can become infected by consuming food or water contaminated with the microscopic parasite.

The most common symptom is watery diarrhea. Other symptoms could include appetite and weight loss, intestinal pain, nausea and fatigue.