What to know about cyclosporiasis, the parasitic illness making Marylanders sick

A nasty bug that causes severe diarrhea is making its way around Maryland and the country.

There are cases of cyclosporiasis every year, but recently there have been many more than usual, and officials aren’t yet sure why.

In Maryland, there have been 32 cases so far this year, with 28 of them since May, according to the Maryland Department of Health. Other states are reporting far more cases, including Michigan, where health officials say there are more than 1,250 cases.

Here’s what you need to know about cases of cyclosporiasis.

What is cyclosporiasis?

The infection is caused by a parasite called Cyclospora cayetanensis that is passed in feces and ingested via contaminated water or food, typically contaminated produce.

For a long time, cases were traced to travel to countries where the microscopic pest is endemic. But U.S. health officials say they have increasingly detected the parasite in both locally grown and imported fruits and vegetables.

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How common is it here?

“There’s always cases, especially in the summer,” said Dr. Miriam Alexander, preventive health physician and medical director for occupational health at LifeBridge Health.

The Maryland Department of Health gathers reports from local health departments and has confirmed 28 cases from the beginning of May through July 7.

By comparison, 18 were reported in the same period in 2025 and 19 in 2024.

Nationally, there are typically about 1,000 cases annually, with the most reported in spring and summer. Maryland had 128 cases last year and 204 the year before.

Alexander said cases have been rising in recent years, but that may be in part due to better diagnostic testing methods.

Why are more people getting sick now?

State health officials say they have not identified a common link among the current cases, but investigations are ongoing.

How can you avoid it?

There isn’t a reliable way to avoid the parasite except by avoiding all fruits and vegetables.

Routine chemical disinfection and sanitization of food and water are unlikely to kill Cyclospora parasites, according to the U.S. Centers for Disease Control and Prevention.

Officials say washing produce thoroughly is still a good practice to avoid foodborne illness. But the best bet in this situation may be cooking vegetables to 185 degrees to try to kill the parasite, as most cases have been linked to raw produce.

The CDC says the parasite has been linked to berries such as raspberries, which have many crevices where the parasite can be difficult to remove. No cases so far have been tied to frozen or canned fruits and vegetables.

Lettuce may also be a source, and officials say to avoid bagged greens and instead buy whole heads of lettuce and peel away the top layers.

“We should always be careful, especially with vegetables and especially from vegetables that are not grown locally,” said Alexander, adding that people should be mindful of eating at reputable restaurants, shopping at quality grocery stores, and reviewing any health citations the eatery might have received.

And, she said, don’t forget to wash your hands, especially after a bowel movement.

What are the symptoms?

The main symptom is watery, sometimes explosive diarrhea, which can last from a few days to a month or longer, according to the CDC. Sometimes it goes away and returns one or more times.

Other symptoms include extreme fatigue, loss of appetite, weight loss, increased gas or bloating, fever and cramps, nausea, and vomiting.

Symptoms usually appear one to 14 days after eating contaminated food or drinking contaminated water, but Maryland health officials say some people are asymptomatic.

What should you do if you think you’ve caught it?

People with symptoms should call their doctors for guidance and to report a possible case.

Most people with healthy immune systems recover without any issues or specific treatment, according to the CDC.

There is no preventive vaccine, but the antibiotic TMP-SMX can be used to help clear an infection.

Also, be sure to rest and drink lots of fluids.