The Centers for Disease Control and Prevention is tracking a major outbreak of cyclosporiasis, a diarrheal illness caused by the parasite Cyclospora cayetanensis. As of mid-July, the CDC has confirmed more than 1,600 cases across 34 states, with over 5,000 additional cases still under review.
This total is nearly six times higher than this point last year. Contaminated lettuce sold to Taco Bell is among the suspected sources of the outbreak.
But cyclosporiasis is far from the only infection that can cause diarrhea and gastrointestinal disease. Most acute diarrheal illnesses in the U.S. are not caused by Cyclospora, but by one of these common culprits.
The Usual Stomach Bug Suspects
Norovirus is the most common cause of acute gastroenteritis in the U.S., responsible for an estimated 19 to 21 million cases each year. It spreads efficiently from person to person and through contaminated food, especially in group settings like cruise ships, schools and restaurants. Symptom onset is rapid — often within 12 to 48 hours of exposure — and typically include vomiting, watery diarrhea and cramping. Fortunately, most infected individuals recover within one to three days.
Salmonella is a bacterial infection usually linked to undercooked poultry and eggs, unpasteurized dairy or contaminated produce. It can cause a fever, stomach cramps and diarrhea that typically start six hours to six days after exposure and generally resolve within a week after symptom onset. Blood in the stool and higher fevers are more common than with norovirus.
Campylobacter is another leading cause of bacterial gastroenteritis and food-borne illness, usually associated with undercooked poultry, raw milk or contaminated water. The CDC estimates that Campylobacter causes over 1.5 million cases each year, although many cases remain undiagnosed. Symptoms usually start two to five days after exposure and can include cramping, a fever and diarrhea that may be bloody. In contrast to norovirus infection, diarrhea resulting from Campylobacter may last for a week, or even longer.
When To Think About Cyclospora
Given the current outbreak, it’s worth knowing what makes cyclosporiasis different from other more common causes of gastrointestinal disease:
- Symptoms persist and can relapse. Untreated, symptoms can last for weeks and may go away and then return. This is uncommon or does not occur with other common causes of diarrheal disease.
- Watery diarrhea plus fatigue and weight loss. Frequent, watery (non-bloody) diarrhea is typical, often with loss of appetite, bloating, nausea and significant fatigue.
- Linked to produce, not poultry. Cyclospora is linked to contaminated fresh produce. Past outbreaks have been caused by bagged salad mixes, fresh basil and cilantro, raspberries, snow peas and green onions — not undercooked meat.
- It’s often missed on routine testing. Standard stool cultures don’t detect Cyclospora and diagnosing it usually requires a clinician to specifically request testing for it.
- The season matters. Cases of cyclosporiasis are most common from May to August in the United States.
Due to the number of pathogens that can cause diarrhea and the nonspecific clinical presentation, it can be challenging to know what is causing gastroenteritis. If your diarrhea is watery, keeps coming back over more than a week and is associated with significant fatigue and/or weight loss — particularly if you’ve recently eaten fresh salad greens, herbs or berries — it’s worth asking your doctor if you should be tested for Cyclospora.
Regardless of the cause, the same food safety steps can help reduce your chances of coming down with a very unpleasant illness. These steps include washing produce thoroughly, cooking food to the recommended internal temperature, avoiding unpasteurized dairy and washing your hands with soap and water after using the bathroom and before preparing or eating food.
