US health officials probe new Cyclospora outbreak after 72 cases

US federal health officials are investigating a new foodborne outbreak driven by Cyclospora cayetanensis, a single-celled parasite that causes diarrhoea. The Food and Drug Administration says 72 new cases have been identified so far in what is the second Cyclospora outbreak reported this year.

Cyclospora is a microscopic parasite that lives in the human intestine and typically spreads to people through fresh produce eaten raw — particularly leafy greens, raspberries and basil — that has been washed or irrigated with water contaminated by the parasite's eggs, known as oocysts. Direct person-to-person transmission is extremely rare.

Typical symptoms of infection include watery diarrhoea, loss of appetite, weight loss, abdominal cramping, bloating, increased gas, nausea and fatigue. Symptoms usually appear about a week after exposure and, if untreated, can last for weeks or even months.

While the illness generally resolves on its own in otherwise healthy adults, it can be longer and more severe in people with weakened immune systems. Diagnosis requires specialised laboratory testing, which can mean some cases go unrecognised for a while.

Outbreak investigations of this kind tend to move slowly, since identifying the source requires both laboratory analysis and painstaking tracing of what patients ate. Officials continue to work backward through the supply chain to pin down the exact source.

That this is the second Cyclospora outbreak reported in the US this year is notable; experts point out that rising temperatures linked to climate change and increasingly global produce supply chains may be raising the frequency of parasite-related illnesses tied to fresh produce.

Health officials advise consumers to wash fresh fruit and vegetables thoroughly before eating them, though Cyclospora oocysts can be fairly resistant to standard washing methods, meaning prevention can't rely on kitchen hygiene alone.

Public-health experts emphasise the importance of reporting outbreaks like this quickly, since early warning helps both consumers avoid at-risk produce and health systems recognise cases faster.

As the investigation continues, public-health observers reiterate concerns that the US's food-safety surveillance capacity has been weakened by recent budget cuts, which they say could slow how quickly outbreaks are detected and traced to their source.

Officials say they will keep updating the investigation as new cases come in and will notify the public once the source is identified. In the meantime, consumers experiencing unexplained, prolonged diarrhoea are advised to see a health professional.