Officials said based on the clinical symptoms of patients, the duration of disease and results of laboratory tests, the cause of the illnesses was norovirus.

Most people infected suffered from vomiting and watery diarrhea but some also reported a fever, nausea and abdominal pain.

Norovirus was isolated as the causative agent in nine fecal samples from infected individuals. Bacillus cereus was also found in one fecal sample.

The investigation showed that the source of infections was not food from a meat shop and it was also not staff, as norovirus was not isolated in employee fecal samples.

It is thought the virus spread to the packaging in which the food was stored after contact with surfaces touched by infected customers. The possibility of previously infected people being responsible was not ruled out by NIJZ.

Officials said one contributing factor was the fact that there were more people in the shop than normal.

Norovirus is a very contagious virus that causes vomiting and diarrhea. People can get it from having direct contact with an infected person, consuming contaminated food or water, or touching contaminated surfaces or objects and then putting their fingers in their mouths.