Lab tests confirmed norovirus in all five samples submitted by people who became sick after the event. However, the exact source of the infection is still unknown. It has not yet been determined whether the virus came from the lake used for the swimming portion of the triathlon or from another source, such as food or surfaces.

The event involved swimming in Laugarvatn, cycling, running, and a post-race gathering with food. Around 40 people have described symptoms such as vomiting and diarrhea on social media, and 22 have officially reported their illness to the Chief Epidemiologist.

Most people began feeling ill the evening or night the day after the event. At least two individuals who did not swim in the lake but attended the event still got sick, and not all those affected had eaten the same food.

Norovirus spreads easily through the so-called "fecal-oral" route — which includes contact with feces, vomit droplets, or contaminated surfaces. It is a common cause of foodborne illness and outbreaks – via food or water.

The South District Public Health Authority has taken water samples from Laugarvatn to test for fecal contamination. Results are expected in the next few days. Testing specifically for norovirus in water however, requires sending samples abroad.

Noroviruses are a group of highly contagious viruses that cause gastrointestinal infections. Typical symptoms include vomiting, diarrhea, stomach cramps, muscle aches, headache, and mild fever. Most people recover within 1–2 days, and there is no specific treatment.

The Chief Epidemiologist has released an online leaflet (in Icelandic) with advice on how to prevent the spread of norovirus.

For more information and prevention tips, visit the Directorate of Health website.

The Chief Epidemiologist