Outbreak of norovirus infection in a hotel in Oslo, Norway, January 2011.

A total of 56 people were affected with gastroenteritis after attending a one-day meeting in a high-quality hotel in the centre of Oslo, Norway, at the end of January 2011. A complete outbreak investigation was carried out. The microbiological investigation confirmed that the outbreak was caused by norovirus. All participants at the meeting were invited by email to complete an online questionnaire asking for information on demographic data, symptoms and food consumption. The results of the epidemiological investigation of the food items served were inconclusive and the source and transmission route of this outbreak remains unclear. However, the environmental investigation highlighted several irregularities in the kitchen that may have enabled the spread of the virus. Specific cleaning procedures and rules were set up for the kitchen staff. As a consequence of this outbreak investigation, the hotel is planning to change its internal routine protocols, for example, samples of food items served at every meal during an event will be stored.