A microscopic parasite called Cyclospora is fueling an outbreak of severe stomach infections across more than a dozen states. Cyclosporiasis, the infection caused by Cyclospora, can cause frequent episodes of explosive, watery diarrhea and usually spreads through fresh produce tainted with trace amounts of human feces.
Over the July 4 weekend, cases of cyclosporiasis in Michigan skyrocketed, from 170 cases as of June 30 to more than 570 in just a few days. Typically, the state only sees around 50 cases a year.
These gastrointestinal fireworks aren’t limited to Michigan. At the beginning of July, the Centers for Disease Control and Prevention (CDC) reported a seasonal outbreak of cyclosporiasis infections, with at least 145 cases in 17 states: Alaska, Colorado, Connecticut, Florida, Georgia, Illinois, Louisiana, Massachusetts, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Tennessee, Texas, Virginia, and Wisconsin.
The agency said the true case count is likely higher, as some people recover without medical care and are not tested.
“The scale of the outbreak and the rate of increase of the Michigan numbers are notable and striking, and we can expect more cases from other states in the weeks to come,” says Peter Chin-Hong, MD, an infectious disease specialist and a professor of medicine at the University of California San Francisco School of Medicine.
The origin of the most current cyclosporiasis outbreak has not yet been pinpointed, according to health officials.
How Cyclosporiasis Spreads
Cyclosporiasis infection occurs when people consume contaminated food and water, according to the CDC. It’s unlikely to be contagious, the agency notes.
While the current case count is high, cyclosporiasis infections are common this time of year, according to public health officials.
“Outbreaks commonly occur between May and August,” says Robert H. Hopkins, MD, the medical director of the National Foundation for Infectious Diseases.
During these late spring and summer months, people tend to eat more fresh fruits and raw vegetables that may carry the parasite responsible for the illness.
Cyclosporiasis is more common in tropical and subtropical countries. The disease spreads in the United States primarily through contaminated imported produce. Previous outbreaks have been linked to the following fresh produce:
- Basil
- Cilantro
- Mesclun lettuce
- Raspberries
- Snow peas
In recent years, Cyclospora has been detected in domestically grown crops. In July 2019, for example, the U.S. Food and Drug Administration found the parasite in two samples of domestically grown cilantro.
How the Cyclospora Parasite Causes Illness
When swallowed, the parasites burrow into the lining of the small intestines and reproduce, Dr. Chin-Hong says.
“The lining of the small intestine gets destroyed, and as a result, loses its ability to effectively absorb water and nutrients from food,” he says.
The gut may also mount an immune response to the parasites, triggering inflammation and swelling.
“The end result is that a large volume of unabsorbed water rushes through the intestine,” says Chin-Hong. “This leads to sudden and forceful high-volume diarrhea that has been described as ‘explosive.’”
Symptoms and Treatment for Cyclosporiasis
Symptoms of cyclosporiasis usually appear 2 to 14 days after exposure and may include:
- Frequent watery diarrhea
- Loss of appetite
- Weight loss
- Stomach cramps and bloating
- Nausea (vomiting is less common)
- Low-grade fever
Cyclosporiasis is not usually life-threatening, and most people typically feel better within a week or two.
Dehydration is a major concern with frequent diarrhea; in severe cases, it can lead to hospitalization, so it’s important to get plenty of fluids if you’re sick.
Anyone experiencing gastrointestinal illness, such as sudden and ongoing diarrhea, should contact their healthcare provider as soon as possible. Your provider can diagnose cyclosporiasis by testing a stool sample.
Along with rest and drinking plenty of fluids to maintain hydration, the illness can be treated with antibiotics such as trimethoprim-sulfamethoxazole (Bactrim). Without proper attention, symptoms can persist and may come back even after improvement.
Most people with healthy immune systems, however, will eventually recover from cyclosporiasis without treatment.
Who Is Most Vulnerable?
In the most recent CDC surveillance of cyclosporiasis in the United States, infected individuals were between ages 5 and 86, and about 3 in 5 were female.
Dr. Hopkins notes that individuals at the highest risk of severe and prolonged diarrhea include young children, the elderly, and those who are immunocompromised, such as people with advanced HIV, organ transplant recipients, and cancer patients.
How to Protect Yourself Against Cyclosporiasis
The CDC says that the Cyclospora parasite is particularly hardy, so routine rinsing or washing of produce is unlikely to kill it.
Heat is needed to reliably get rid of the parasite, so Michigan state health officials advise consumers to cook their food to 158 degrees F or higher when they can.
While not as dependable, cleaning practices can also lower risk. Health authorities recommend:
- Wash your hands before and after preparing food.
- Wash all fruits and vegetables thoroughly under running water before eating, cutting, and cooking.
- Scrub firm fruits and vegetables, such as melons and cucumbers, with a clean produce brush.
- Cut away any damaged or bruised areas on fruits and vegetables before preparing and eating.
Read the full article here

