Outbreak of Diarrhea-Causing Parasite Grows to More Than 1,000 Cases

Nearly 1,000 people in Michigan have gotten sick from a tiny parasite that can cause weeks of watery diarrhea. The parasite is called cyclospora, and this is the largest outbreak of its kind in Michigan's history. Health officials say it is also one of the biggest outbreaks in the whole country in several years. No one has died, but about 40 people have been hospitalized.

Michigan officials first noticed the outbreak in late June, when they found about 170 cases in the southeastern part of the state. By Wednesday, that number had jumped to 992. Just across the state border in Lucas County, Ohio, another 306 cases were reported, with more than 400 total in northwest Ohio. Michigan usually only sees about 50 cases of cyclospora each year, so this spike is very unusual.

Dr. Natasha Bagdasarian, Michigan's top health official, told the Associated Press that 'there is clearly a linked outbreak happening right now.' Investigators are also looking into similar illnesses in 28 other states. However, the source of the outbreak — meaning the food that is making people sick — has not yet been found. Finding the source can take months, and sometimes investigators never figure it out.

Cyclospora is a microscopic, round-shaped parasite. It infects the intestines and spreads through feces, which is human or animal waste. People usually get infected by eating fruits or vegetables that were watered with contaminated water. The illness it causes is called cyclosporiasis, and it is not usually life-threatening. Doctors treat it with antibiotics.

Outbreaks of cyclospora most often happen in late spring and summer. The number of U.S. outbreaks started rising about ten years ago, partly because of climate change and better ways of testing for the illness. Past outbreaks have been linked to foods like raspberries, basil, and cilantro. This year's case total is already four times higher than it was at the same point last year.

Researchers say cyclospora is hard to track for several reasons. Some lab tests used to check for food poisoning are not designed to detect cyclospora, so many cases go unreported. Scientists also cannot grow the parasite in a lab, which makes it harder to find evidence. On top of that, contaminated food is sometimes sold at both grocery stores and restaurants, making it tricky to figure out where the tainted food came from.

Health officials say people whose diarrhea has not gone away after a few days should see a doctor and mention the possibility of cyclospora. The best way to avoid getting infected is to not eat food or drink water that may be contaminated. Michigan officials suggest buying whole heads of lettuce instead of pre-washed, bagged salad mixes. They also recommend removing the outer two or three leaves and washing the rest under running water, and cooking vegetables when possible.