The Cyclospora Outbreak, By the Numbers

A major outbreak of a stomach illness called cyclosporiasis swept across the United States this summer, making nearly 13,000 people sick. The illness is caused by a tiny parasite called Cyclospora cayetanensis, found in contaminated food or water. Health officials traced the outbreak to iceberg lettuce sold by a company called Taylor Farms de Mexico. The Centers for Disease Control and Prevention, known as the CDC, announced that the outbreak is now over.

This was the largest outbreak of cyclosporiasis ever recorded in U.S. history. In a typical year, only a few thousand Americans get this illness. Between 2018 and 2022, the average was just 3,285 cases per year. This summer's outbreak was nearly four times that amount, which alarmed public health officials across the country.

People get infected with the Cyclospora parasite by eating or drinking something contaminated with it. In the United States, outbreaks have often been linked to fresh fruits and vegetables. Some infected people may not feel sick at all, but others experience serious stomach problems, including what doctors describe as 'explosive' diarrhea. The illness can also cause nausea, fatigue, and cramping.

In July, health officials announced they were looking into the outbreak across several states. They eventually linked it to processed iceberg lettuce from Taylor Farms de Mexico. On July 17, the company recalled all of its iceberg lettuce products from central Mexico. The company said it acted 'out of an abundance of caution' to protect people from getting sick.

At the peak of the outbreak, the CDC was reporting more than 1,000 new cases in a single day. After the lettuce recall, that number dropped sharply. By August, fewer than two new cases were being reported each day. The CDC said there is now no risk from this source because all of the affected lettuce has passed its expiration date and is no longer available.

Sadly, two people died from the illness — both in Michigan. State health officials said both individuals had serious health conditions before they got sick, and those conditions may have made the illness worse. Cyclosporiasis rarely causes death in otherwise healthy people, and most recover without medical treatment. Still, of the nearly 12,883 confirmed cases, 570 people were sick enough to be hospitalized.

Michigan was hit hardest, with more than 5,700 cases reported there. Ohio came in second with 2,871 cases, and Missouri had 1,071. Other states with hundreds of cases include Indiana, Kentucky, Kansas, Nebraska, Illinois, Pennsylvania, and Oklahoma. In all, 21 states were affected by the outbreak.

The CDC noted that the true number of infected people is likely even higher than 12,883. Many people recover on their own without seeing a doctor, so they are never tested for the parasite. The Food and Drug Administration is still investigating how the lettuce became contaminated. Officials hope that finding answers will help prevent future outbreaks from happening.