Brits are being warned about a parasite that is believed to be entering the UK via holidaymakers who have been abroad.
The parasite, known as cyclospora cayetanesis, is spread when food or water is contaminated with infected human faeces.
This causes an illness called cyclosporiasis, with those affected often suffering from explosive diarrhoea.
Is cyclosporiasis contagious?
The UK Health Security Agency's (UKHSA) website explains that anyone with cyclosporiasis can't pass it on to another person, so if you know someone unwell, you won't catch this parasite from them.
Karen Hutchinson, prescribing pharmacist at Chemist4U, said: “Cyclospora cayetanesis is a parasite that infects the small intestine and causes an illness known as cyclosporiasis, commonly associated with explosive diarrhoea.
“The parasite is often found in certain parts of Central and South America, Southeast Asia, the Middle East and Africa.
“However, the UK Health Security Agency has now issued a warning to Brits returning from Mexico, after 67 cases of cyclosporiasis were reported in the UK, with most involving those returning from certain areas of Mexico.
“The news comes following an outbreak in the United States which has seen potentially more than 18,000 people infected, across 45 states.”
The 67 cases in the UK have been recorded since April, which the UKHSA says is "already most of a typical year's total".
What are the symptoms of cyclosporiasis?
You can expect cyclosporiasis symptoms to appear about a week after you've been exposed, so this can make it tricky to understand exactly how and when you contracted it.
Common symptoms include:
- watery diarrhoea
- stomach cramps
- nausea
- fatigue
- bloating
- wind
- tiredness
- muscle aches
- loss of appetite or weight
Some people may also experience:
- fever
- vomiting
Karen adds: “Without treatment, these symptoms can persist for several weeks, if not longer.
“Most people who have a healthy immune system will recover without treatment.
Travelling to Mexico this summer? We've seen a sharp rise in cyclospora infections linked to the destination.
The tiny parasite is picked up through contaminated food, even at high-end all-inclusive resorts and causes explosive diarrhoea. pic.twitter.com/dPIRLJdYxC— UK Health Security Agency (@UKHSA) July 30, 2026
“However, if you have a weakened immune system then you will be more vulnerable and should seek medical advice as symptoms may last longer.”
She adds that while the risk is currently low for people in the UK, it's important to know what the symptoms are.
Karen explains: “If you recently returned from a country experiencing an outbreak, regularly eat uncooked fresh produce (such as salad leaves or raw vegetables), or suspect you have drunk contaminated water, then you are likely to be at greater risk of infection.
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“Anyone that has persistent diarrhoea, is unable to keep fluids down or notices signs of severe dehydration should seek medical assistance immediately.”
If you can, “drink plenty of fluids to reduce the risk of dehydration”.
Don't prepare food for others and make sure you maintain good hand hygiene.
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