Michigan's explosive outbreak of diarrheal parasite jumps to over 1,200 cases - Ars Technica

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Cases of an explosive diarrheal parasite continue to skyrocket in Michigan, which is reporting 1,251 cases as of July 9. Of those, 44 were hospitalized. Meanwhile, across the border in Ohio, cases are also quickly rising, with news reports of a case total over 500.

The outbreak in Michigan began with two cases reported on June 22 and rose steeply at the start of July. The Michigan Department of Health and Human Services (MDHHS) reported 572 cases on July 4. On Wednesday, July 8, 239 cases were reported, the highest single-day tally so far. The current total of 1,251 cases includes 159 case reports received on July 9.

The epicenter of the outbreak is in the southeastern corner of the state, where health officials from multiple jurisdictions are working furiously to identify and interview cases to track the source or sources of the parasite, which spreads through food and water.

Microscopic menace

That parasite is Cyclospora cayetanensis, a microscopic, single-celled protozoan that is shed in feces and typically infects humans in the US via contaminated produce, though it can also spread in contaminated drinking water. In recent years, the US has been logging between 2,000 and 5,000 cases each year, with the parasite thriving in the summer months. Cases are typically highest in June and July.

While it is still unclear whether this will be a record year for cyclosporiasis cases nationally, it’s certain that Michigan is experiencing an unprecedented outbreak. In past years, the state’s yearly case totals have mostly been around 50; the case tally just in July is already 25 times larger than that usual number. And cases continue to rise, while investigators have not yet identified how people are getting sick.

Cases are also surging across the border from southeastern Michigan into northwestern Ohio. According to the Associated Press, counties in the region have seen more than 500 cases, with Lucas County alone reporting 306 cases as of Wednesday.

Transmission and treatment

Health experts say transmission is most likely through contaminated food—not human-to-human transmission. After the parasite spreads from stool, it takes one to two weeks in the environment for it to become infectious. Once infected, a person usually begins experiencing symptoms about a week later, though onset can range from two days to over two weeks. The main symptom is “watery diarrhea with frequent and sometimes explosive bowel movements,” though a person can also experience nausea, fatigue, cramping, and bloating. Without treatment, the diarrhea can continue for a month or longer. A primary concern is dehydration.

People who begin experiencing diarrhea should contact a healthcare provider to determine if it’s cyclosporiasis, which can be treated with the combination antimicrobial trimethoprim-sulfamethoxazole, sold as Bactrim.

Prevention

MDHHS is advising people to be cautious about certain produce that has been linked to past cyclosporiasis outbreaks. Officials recommend people avoid bagged lettuces and buy whole heads instead, removing the outer two or three leaves before washing the inner leaves thoroughly. Green onions should be trimmed, and outer layers should be removed before thoroughly washing. Cilantro, basil, and snow peas should be thoroughly washed under running water. For raspberries, which the parasite can cling to and be hard to clean, MDHHS advises people to cook them or at least stick to frozen berries—freezing reduces the risk of the parasite, though it doesn’t eliminate it. In all, the safest choice is cooking.

Beth Mole

Senior Health Reporter

Beth Mole

Senior Health Reporter

Beth is Ars Technica’s Senior Health Reporter. Beth has a Ph.D. in microbiology from the University of North Carolina at Chapel Hill and attended the Science Communication program at the University of California, Santa Cruz. She specializes in covering infectious diseases, public health, and microbes.

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