Cases of the intestinal illness Giardia in England have reached their highest level since 2016, according to new data from the UK Health Security Agency (UKHSA). The agency has issued a warning ahead of the autumn months, when cases of the illness generally peak.
Rise in confirmed cases
UKHSA data shows that Giardia cases in England rose from 5,450 in 2024 to 6,069 in 2025 – an increase of 11.4%. London reported 1,568 cases, while the North West reported 1,029.
Giardia is an intestinal illness commonly described as a “stomach bug” because of its symptoms. It is caused by a microscopic parasite that targets the small intestine rather than the stomach itself. According to the UKHSA, the most common symptom is diarrhoea, which is often accompanied by abdominal cramps, bloating, burping, wind and weight loss.
Autumn peak and precautions
Cases of Giardia peak in autumn, with 599 cases confirmed last October. Meanwhile, there were 580 in September and 574 in November.
The UKHSA is warning people to be vigilant over the upcoming months. They urge Brits to maintain good hygiene to prevent the illness, including washing hands with soap and water after using the toilet.
The agency said: “The number of laboratory-confirmed cases reported each year returned to pre-pandemic levels in 2023 and has risen since. UKHSA is investigating the reasons for this, but it is possibly due to a mix of factors, including new and more effective testing, increased travel since the pandemic and climate and environmental changes.”
Travel advice and symptoms
People can catch the illness in the UK as well as abroad. It spreads through direct contact with infected people or animals, or by swallowing contaminated food or water. According to the UKHSA, infections have been seen in returning travellers from Southern Asia, South-Eastern Asia, Africa and South America.
The agency continued: “International travellers should take precautions when travelling abroad to reduce the risk of infection. This includes drinking bottled water rather than tap water and consuming cooked food rather than raw items such as salad vegetables washed in tap water.” Travellers should also be mindful when swimming in rivers, lakes and the sea while abroad, as water can sometimes be contaminated.
Nicola Love, Senior Food Safety Surveillance Lead at UKHSA, said: “We are seeing a rise in giardiasis in the UK. Symptoms can last from weeks to several months and if left untreated, it can cause serious complications especially in young children, the elderly and those with weakened immune systems.”
She added: “There are some simple precautions everyone can take to reduce their risk, whether you are planning an autumn getaway somewhere warm or staying in the UK. Good hygiene can help prevent giardiasis and other common gastro illnesses. Wash your hands with soap and water after using the toilet, after changing nappies, and before preparing food.”
Love also said: “Encourage children to wash their hands regularly too. If you have a Giardia infection, continue to hydrate yourself and see your GP, do not go swimming until 2 weeks after your diarrhoea has stopped. Parents should contact their GP or NHS 111 if they or their children are ill with dehydration, or if diarrhoea worsens or lasts longer than 3 days.”
