Giardia: guidance and data

The symptoms and epidemiology of giardiasis including travel-associated infections.

Giardia is a parasite which can grow in the intestines of infected humans or animals and cause giardiasis. Diarrhoea is the most common symptom of giardiasis. Other symptoms include abdominal cramps, bloating and flatulence.

More information about giardiasis is available on NHS choices.


Giardiasis can be transmitted by direct contact with infected animals or humans, or by consumption of water, food or beverages contaminated by the faeces of infected animals or humans. People may also be infected by swimming in contaminated water (for example in lakes or rivers). Many cases are associated with foreign travel.

The incubation period - the delay between infection and the appearance of symptoms - is 5 to 25 days.


For laboratory reports of Giardia infections from 2006 to 2015, see attached document. This includes total cases per year in England and Wales, plus regional, age and sex, and seasonal data for 2015.

Giardia data 2006 to 2015 (PDF, 285KB, 7 pages)

Travel-associated infections

Travel-associated Giardia infection: 2014 (PDF, 165KB, 9 pages)

Published 1 April 2014
Last updated 28 February 2017 + show all updates
  1. Added travel-associated Giardia 2014 report.
  2. Added Giardia data for England and Wales from 2006 to 2015. Deleted text and graphs from epidemiology section.
  3. First published.