More than 3,300 cases reported in Michigan parasite outbreak

More than 3,300 people have been infected in a rapidly growing cyclosporiasis outbreak in Michigan that health officials believe may be linked to lettuce or salad greens. At least 44 people have been hospitalized.

The Michigan Department of Health and Human Services (MDHHS) reported 3,309 cases on Tuesday, an increase of 669 from Monday. Michigan typically records only 40 to 50 cases in an entire year.

Health officials said early findings repeatedly identified lettuce as a food eaten by people who became sick, but no specific type of produce, grower or supplier has been linked to the outbreak. Other foods have not been ruled out.

The outbreak was first identified on June 29. More than 1,000 patients have since been interviewed as state, local and federal investigators work to trace the source through complex food distribution networks.

At least 31 other states have also reported cases of cyclosporiasis, according to an ABC News tally.

Cyclospora is a parasite that infects the intestines and is usually contracted by consuming contaminated food or water. Symptoms can take up to two weeks to appear and include frequent watery diarrhea, nausea and stomach cramps.

Michigan health officials recommended buying whole heads of lettuce instead of bagged lettuce or premixed salad kits, discarding the outer two or three layers and washing the remaining leaves under running water. Washing alone cannot guarantee the parasite will be removed.

Cooking greens to at least 158 degrees Fahrenheit kills cyclospora. People experiencing frequent watery diarrhea were advised to contact a health care provider and specifically request testing for the parasite because routine stool tests may not detect it. Cyclosporiasis can be treated with antibiotics.