Giardiasis cases are rising in England: should we be worried?

Cases of giardiasis, an intestinal infection that causes diarrhoea, bloating and gas, have reached their highest level in England since 2016 according to newly published data by the UK Health Security Agency (UKHSA).

The agency reported 6,069 lab-confirmed cases of giardiasis in 2025, an 11.4% rise from 2024. It is the highest yearly total in almost a decade.

This rise might sound alarming. But while the increase in cases is real, it doesn’t necessarily mean that England is facing a crisis. Instead, the rise is probably happening for a mix of reasons, including: increased international travel in the post-pandemic era; upgrades to lab testing; changes in rainfall and flooding; and better awareness of Giardia duodenalis – the tiny parasite that infects the small intestine.