Michigan Cyclospora outbreak tops 1,200 cases

Michigan health officials are investigating an unusually large Cyclospora outbreak that has reached 1,251 reported cases, including 44 hospitalizations, as of July 9. The rise matters because the parasite can cause prolonged diarrhea and investigators have not yet identified the food or water source making people sick.

The Michigan Department of Health and Human Services said the outbreak began with two cases reported June 22, then rose sharply in early July. The department reported 572 cases on July 4, followed by 239 new reports on July 8, the highest one-day total so far, and 159 more on July 9.

The largest concentration is in southeastern Michigan, where local and state health officials are trying to interview patients and trace possible exposures, according to MDHHS. The agency says the parasite spreads through contaminated food or water.

Cases also rising in Ohio

Northwestern Ohio is seeing a similar increase. The Associated Press reported that counties in that region have recorded more than 500 cases, including 306 in Lucas County as of Wednesday.

The parasite involved is Cyclospora cayetanensis, a microscopic single-celled organism passed in feces. In the United States, infections are most often tied to contaminated produce, though contaminated drinking water can also spread the parasite, according to health authorities cited in the reports.

U.S. case counts have typically ranged from 2,000 to 5,000 a year in recent years, with infections peaking in the warmer months, especially June and July. Michigan’s current outbreak is far above its usual annual burden; the state has generally reported about 50 cases a year in past years, while the July total alone is already about 25 times that level, according to MDHHS figures described in the reports.

Symptoms and treatment

Health experts say person-to-person spread is unlikely because Cyclospora usually needs one to two weeks in the environment after being shed before it can infect someone. Once infected, people often develop symptoms about a week later, though onset can occur from two days to more than two weeks after exposure.

The main illness is watery diarrhea with frequent bowel movements. Patients may also have nausea, fatigue, abdominal cramps and bloating, and untreated diarrhea can last a month or longer, according to health guidance cited in the reports. Dehydration is a major concern.

People with diarrhea are being advised to contact a health care provider to determine whether they have cyclosporiasis. The illness can be treated with trimethoprim-sulfamethoxazole, an antimicrobial combination sold as Bactrim.

Produce precautions

MDHHS is urging caution with produce that has been linked to prior cyclosporiasis outbreaks. The agency recommends choosing whole heads of lettuce instead of bagged lettuce, discarding the outer two or three leaves and washing the inner leaves well.

For green onions, MDHHS advises trimming them, removing outer layers and washing thoroughly. Cilantro, basil and snow peas should be rinsed under running water. For raspberries, which can be difficult to clean because the parasite can cling to them, the department says cooking is the safest option; frozen berries may reduce risk but do not remove it.

This story draws on original reporting from Ars Technica.