Thousands of people in the United States and travellers from several countries returning from Mexico have been infected with a parasite that causes severe diarrhoea, prompting health authorities to remind international travellers of food and water safety precautions.
The cyclospora parasite can be found worldwide but usually occurs in low-income, tropical, and sub-tropical countries where it is often endemic. It can contaminate soil and other surfaces, water, and fresh food, and humans contract it through the “oral-faecal” route, usually by swallowing contaminated water or eating contaminated fresh produce.
Travelling to Mexico this summer? We've seen a sharp rise in cyclospora infections linked to the destination.
— UK Health Security Agency (@UKHSA) July 30, 2026
The tiny parasite is picked up through contaminated food, even at high-end all-inclusive resorts and causes explosive diarrhoea. pic.twitter.com/dPIRLJdYxC
Symptoms of the infection typically appear around a week after exposure and are described by the World Health Organization as “watery diarrhoea, abdominal cramping, weight loss, anorexia, myalgia, fatigue, and occasionally vomiting and fever.”
Around 18,000 people across 45 US states have contracted the parasite since May 2026, according to the US Centers for Disease Control and Prevention (CDC). The outbreak has been traced to iceberg lettuce grown in Central Mexico by a supplier to the fast-food chain Taco Bell. Two people in Michigan are reported to have died after the infection was compounded by underlying medical conditions. However, authorities emphasise the infection is rarely fatal and often resolves by itself or, in particularly severe cases, with antibiotic treatment.
Health authorities in the United Kingdom have also reported an increase in travel-related infections. Between 30 April and 15 July 2026, the UK Health Security Agency (UKHSA) recorded 67 cases, 48 of which affected people who had recently returned from holidays in all-inclusive resorts in the Riviera Maya and Cancun regions of Mexico. As a result, the UK’s Foreign, Commonwealth and Development Office (FCDO) updated its travel advice for Mexico to include information on the outbreak.
While no widespread outbreaks have been reported elsewhere, the rise in cases serves as a reminder that travellers can be exposed to food- and water-borne illnesses even when staying at high-end resorts. Contaminated fresh herbs, salads, and soft fruits are among the most common sources of cyclospora outbreaks. Health experts also stress that the parasite is not spread directly from person to person.
Dr Philip Veal, Consultant in Travel Health at UKHSA, said travellers to regions where the parasite is common “can reduce their risk by following good food and water hygiene measures, including drinking bottled water and eating thoroughly cooked food, even when staying in high-end all-inclusive resorts. We also advise avoiding certain foods such as fresh uncooked berries and herbs, unpeeled fruit, and salad items.”
The advice is relevant to travellers regardless of nationality, particularly those visiting destinations where Cyclospora infections are known to occur. Veal added: “If you develop symptoms after returning from travel, such as watery diarrhoea, loss of appetite, weight loss, stomach cramps or pain, bloating, increased wind, nausea, fatigue or other flu-like symptoms, please seek medical attention and inform your healthcare professional of your travel history.”
Travellers should also consult their national travel health authorities before departure and follow local food and water hygiene recommendations while abroad. The TravelHealthPro website has more information on the steps travellers can take to keep themselves and everyone in their party well.
