Diarrhoea parasite spreads across US as more than 10,000 cases recorded

Outbreak of Cyclospora parasite spreads even further across United States Wed 5 Aug 2026 at 1:02pm A parasitic infection that causes diarrhoea has now reportedly spread across more than a dozen states in the US after officials blamed contaminated lettuce for the outbreak. The Cyclospora parasite causes diarrhoea, nausea, and sometimes vomiting; without treatment, symptoms can last for more than a month. The US Centers for Disease Control and Prevention (CDC) has officially linked the outbreak to nine states. Local media, including The Washington Post, have predicted this number will soon increase to at least 15 states. At least two deaths have also been reported in Michigan, the first fatalities associated with the outbreak. What is Cyclospora? Cyclosporiasis is an intestinal infection that can be contracted by consuming raw fruit and vegetables or water contaminated with the cyclospora parasite. The microscopic parasite is transmitted via faecal matter. It is also notoriously difficult to detect, according to professor Shokoofeh Shamsi, a parasitologist at Charles Sturt University. "It's very easy for it to just penetrate through different aspects of our lives and infect us," she said. Though the infection is rarely life-threatening, children, older people and immunocompromised people are at risk of serious illness stemming from it. Loading...Both people who died earlier this week, according to Michigan health officials, had underlying health conditions that may have been impacted by dehydration and the infection. "Any time we get complacent, an outbreak is going to happen," Professor Shamsi said. "Now the US, a leader in global health, is just really unable to control this outbreak. "The two deaths [are] definitely the tip of the iceberg. Whatever you see, there is more beneath the surface." How did this Cyclospora outbreak start? The Food and Drug Administration (FDA) has linked the outbreak to iceberg lettuce sourced from central Mexico. The lettuce, supplied by Taylor Farms de Mexico, was served at Taco Bell locations in multiple states. Taylor Farms has since announced a recall for the lettuce products sourced from Mexico, distributed to 27 states between June 29 and July 16. The same supplier was linked to a 2013 Cyclospora outbreak, which spread across multiple states and infected hundreds of people. An investigation into reported cases and contaminated products is ongoing by the FDA and the CDC, which said they expected to see the number of confirmed cases rise despite the product recall. Former FDA commissioner Scott Gottlieb said weather conditions had raised the risk of contamination. Raw sewage could have reached farmed areas through flooding or a breach, he added. "There was some event that happened in central Mexico, we don't know what yet," he told CNBC. "That led to a lot of fields probably getting contaminated." Analysts in Mexico said they were waiting for the results of official investigations. Mexico has only recorded a handful of cases since the infection began to spread. While the majority have been linked to Taylor Farms, at least two other outbreaks under investigation have an unknown source. Democratic congressman Josh Gottheimer blamed cuts to the FDA and CDC during the second Trump administration for the lack of surveillance. Mr Gottheimer said the CDC had fired more than 70 per cent of the team responsible for tracking Cyclospora and other parasites since 2025. How many cases of cyclosporiasis have been recorded so far? As of August 3, the CDC had received reports of 10,468 cases of confirmed cyclosporiasis. An additional 12,255 cases are still unconfirmed, and health officials have indicated these numbers likely represent only a fraction of the total outbreak. To date 47 states have reported cases and at least 517 people have been hospitalised. Dr Gottlieb has told media he believed cases were being under-reported. The true number, he said, was likely 10 to 20 times what had been recorded. "This is the largest outbreak we've ever seen in the history of Cyclospora," he said. In Michigan, the state at the centre of the outbreak, officials have recorded 11,508 total cases, well above the CDC's total confirmed caseload. The CDC does not include probable cases, meaning the numbers vary depending on whether state officials are combining probable and confirmed cyclosporiasis. Michigan's chief medical executive, Natasha Bagdasarian, said local health departments were interviewing patients about what they ate and where it came from. The information was being entered into a statewide database. "There's a lot of tracing back that we have to do," Dr Bagdasarian said. "[It's] not just in terms of where people got their produce from, but then tracing that back to its very origins and finding where along the pathway the contamination occurred." How do you control the spread of Cyclospora? For a single-celled organism, according to Professor Shamsi, cyclospora is "really difficult to kill". "The only thing we know that is 100 per cent effective is high temperature and proper cooking," she said. "But we don't want to cook our salads … and it's highly recommended by health professionals as well to consume salads and raw vegetables on a daily basis. "It's not only on the public to be aware … but largely it's on policymakers and everyone in the food safety sector to have a very well designed supply system that is based on prevention. "And if [the parasite] does make it through, they need proper surveillance and monitoring to remove those products from the food system." There have been no outbreaks of cyclosporiasis in Australia to date, according to the Australian Drinking Water Guidelines. Sporadic cases have been associated with international travel.