A microscopic parasite called Cyclospora is fueling an outbreak of severe stomach infections across at least 34 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.
On Friday, July 24, the Centers for Disease Control and Prevention (CDC) said it had received reports of 4,173 confirmed domestic cases, and more than 7,400 unconfirmed cases pending further testing. Michigan and Ohio reported a notable recent surge in illness, as per this week’s CDC briefing.
The agency said the true case count is likely higher, as some people recover without medical care and are not tested. Officials in Michigan, one of the hardest-hit states, have reported more than 8,176 cyclosporiasis cases as of July 24. Typically, the state only sees around 50 cases a year.
The CDC is now investigating multiple clusters of Cyclospora cases, including a multistate outbreak that’s been linked to iceberg lettuce served at Taco Bell.
“This is much higher than what we’ve seen last year or the year before,” said Gwen Biggerstaff, ScD, deputy director of CDC’s Division of Foodborne, Waterborne, and Environmental Diseases, in a press conference on July 21. “We anticipate continuing to see cases increase, possibly through the end of August, which is the end of the cyclosporiasis season.”
How Cyclosporiasis Spreads
Cyclosporiasis infection occurs when people consume contaminated food and water, according to the CDC. It’s unlikely to spread from person to person, 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:
Parsley
Cilantro
Basil
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 (FDA) found the parasite in two samples of domestically grown cilantro.
The FDA is investigating multiple outbreaks around the country. Investigations into cases in North Carolina are ongoing; and authorities are looking into cilantro and parsley as common culprits, although their involvement in the current outbreak isn’t clear.The outbreak in North Carolina doesn’t appear to be linked to one in Michigan and surrounding states involving Taco Bell.
The FDA said the Michigan outbreak now includes cases in nearby Illinois, Indiana, Kansas, Kentucky, Ohio, Oklahoma, Pennsylvania, and West Virginia. Illnesses were traced back to a single supplier of shredded lettuce from Mexico, Taylor Farms. According to the CDC, shredded iceberg lettuce from other stores or restaurants hasn’t been affected.
On July 17, Taylor Farms voluntarily recalled iceberg lettuce imported from Mexico due to its potential for Cyclospora contamination. This recall includes lettuce from retail stores and restaurants. Taco Bell has also since removed all Taylor Farms lettuce from its food as a precaution.
How the Cyclospora Parasite Causes Illness
When swallowed, the parasites burrow into the lining of the small intestines and reproduce, 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 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 Dr. 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.
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.
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. Remove outer leaves of lettuce and cabbage.
