US health officials have traced an outbreak of the parasite cyclospora to iceberg lettuce served at Taco Bell restaurants. The parasite causes a diarrheal illness that can be severe, with symptoms including watery diarrhea, stomach cramps, nausea, and fatigue. The contamination may not be limited to Taco Bell, as officials warn that other food sources could also be affected. Cyclospora is a microscopic parasite that is typically spread through contaminated food or water. Outbreaks often occur when produce is grown or washed with contaminated water. The illness can last from a few days to several weeks, and treatment usually involves antibiotics. Health authorities are investigating the source of the contaminated lettuce and have advised consumers to be aware of symptoms. To prevent infection, people should wash fruits and vegetables thoroughly, though this may not eliminate cyclospora entirely because it can be resistant to chlorine. Cooking food kills the parasite. The US Food and Drug Administration (FDA) is working with Taco Bell and suppliers to identify the exact source of the tainted lettuce. The outbreak has prompted a review of food safety practices in the fast-food industry. While no deaths have been reported, the illness can be serious for individuals with weakened immune systems. Health officials urge anyone who ate at Taco Bell and developed diarrhea to seek medical care and report their illness to local health departments.