Giardiasis cases rising in England: what's behind the numbers and how to reduce risk

Overview

The Conversation reports that giardiasis cases in England reached 6,069 lab-confirmed in 2025, the highest since 2016, according to UK Health Security Agency data. While the rise is real, it is unlikely to signal a crisis, and multiple factors are likely at play.

• Travel rebound after the pandemic contributes to imported infections.
• Upgrades to laboratory testing increase detection and sensitivity.
• Changes in rainfall and flooding can affect water quality and Giardia exposure.
• Increased awareness and reporting of Giardia infection improve case capture.

Author: The Conversation

Overview

England has seen a notable rise in giardiasis, with 6,069 lab-confirmed cases in 2025—the highest annual total in almost a decade, according to data published by the UK Health Security Agency (UKHSA). The year-on-year increase from 2024 was 11.4%. While this uptick is real, health experts emphasise that it does not automatically indicate a public health crisis. The rise is likely due to a confluence of factors including increased international travel in the post-pandemic era, upgrades to laboratory testing, shifts in rainfall and flooding affecting water quality, and greater awareness of Giardia duodenalis, the parasite that causes giardiasis.

What is giardiasis?

Giardiasis is an intestinal infection caused by Giardia parasites. It commonly leads to diarrhoea, bloating, and gas, and in longer or more severe cases can cause weight loss and prolonged fatigue. Symptoms typically begin one to three weeks after exposure. Not everyone who becomes infected shows symptoms; some people can carry and spread the parasite without realizing it.

How does it spread?

Transmission occurs primarily via the faecal-oral route. Giardia cysts in infected feces can be swallowed, even in small numbers. The well-known route is through contaminated drinking water or food, but person-to-person spread in households and nurseries, and contact with infected animals, are also important routes. International travel to regions with poorer sanitation increases exposure risk. The article also notes emerging attention to sexual transmission through activities that involve oral contact with the anus or contact with fecal material on hands or sex toys.

Why are cases rising?

Experts point to multiple, overlapping causes. First, testing capacity in NHS laboratories has expanded, with upgraded equipment enabling more sensitive and broader detection of enteric illnesses in a single sample. This diagnostic improvement means more cases are identified that might have been missed previously. Second, travel levels are rebounding after Covid restrictions, which increases opportunities for imported Giardia infections. Third, environmental factors such as heavy rainfall and flooding can contaminate water supplies, raising exposure risk. Finally, increased awareness and reporting of giardiasis contribute to higher observed case totals.

Don’t panic, but take precautions

Giardiasis is typically not fatal for healthy adults, but symptoms can be long-lasting and affect quality of life. Seek medical advice if diarrhoea lasts more than seven days, if there is blood in the stool, or if contact with an infected person is suspected. Practical prevention steps include thorough hand washing with soap, particularly after diaper changes, animal contact, and toilet use. Additional measures during and after sexual activity may help reduce transmission, and travellers should avoid drinking untreated water and avoid swallowing water while swimming. If you have diarrhoea, avoid swimming until fully recovered for two weeks. The piece highlights that giardiasis has been under-recognised for years, and rising case counts may reflect both improved detection and genuine changes in risk, underscoring the ongoing importance of water and food safety in public health.

Bottom line

While the rising numbers warrant attention, the story is not simply one of growing danger. The combination of better testing, travel rebound, environmental factors, and awareness likely drives the observed increase. Public health remains focused on reducing exposure to water- and food-borne infections and on supporting patients who experience prolonged symptoms.