Cases of Giardia, a parasite causing diarrhea and other gastrointestinal issues, have reached their highest levels in Britain since 2016, according to the UK Health Security Agency (UKHSA).
The agency reported an 11 percent increase in cases over the past year, rising from 5,450 in 2024 to 6,069 in 2025. London recorded the highest number of infections with 1,568 cases, followed by the North West with 1,029.
Giardia is caused by a microscopic parasite and its symptoms can include diarrhea, abdominal cramps, flatulence, unexplained weight loss, and fatigue. While generally treatable with antibiotics, untreated infections can lead to malnutrition and stunted growth in children, and serious complications in the elderly or those with weakened immune systems.
Health officials are investigating the reasons for the surge, citing potential factors such as more effective testing, increased travel post-pandemic, and climate changes. Cases peaked in autumn, with 599 people falling ill in October.
Nicola Love, Senior Food Safety Surveillance Lead at UKHSA, emphasized the importance of good hygiene to prevent the spread of Giardia and other gastrointestinal illnesses. "Wash your hands with soap and water after using the toilet, after changing nappies, and before preparing food. Encourage children to wash their hands regularly too," Love stated.
Precautions for travelers include drinking bottled water instead of tap water and consuming cooked food over raw items like salads washed in tap water. Swimmers are also advised to exercise caution in rivers, lakes, and the sea where water may be contaminated.
The UKHSA advises individuals with Giardia infection to stay hydrated, consult their GP, and avoid swimming for at least two weeks after their diarrhea has stopped. Parents are urged to contact their GP or NHS 111 if their child shows signs of dehydration or if diarrhea worsens or persists for more than three days.
This rise in cases follows the 2024 deaths of two children at Millstead Primary School, where a Giardia outbreak occurred. However, the UKHSA stated it was unlikely the deaths were linked to the outbreak.