Norovirus on swabs taken from hands illustrate route of transmission: a case study

Recently, environmental swabs from kitchen and bathroom surfaces have been described as an additional tool for the detection of norovirus in outbreak settings. This article describes an outbreak investigation in response to the reporting of gastroenteritis in three unrelated groups of 6, 12, and 13 adults approximately 30 h after having meals in the same restaurant. Fecal samples were collected from 13 patients and six food handlers, and environmental swabs were taken from the soap dispenser, working bench, doorknobs of cupboards, and the grip of a knife in the kitchen and in bathrooms as well as from the hands of each of three employees on the day of inspection. Clinical and environmental samples were analyzed separately in time and location for the presence of norovirus by real-time reverse transcription PCR. Structured interviews revealed that all staff members had suffered from gastroenteritis, one after the other. Norovirus RNA (GGI.6) was detected in 17 of 19 fecal samples as well as in 4 environmental samples, including a swab sample from the hands of a staff member who was preparing ready-to-eat food. Sequences obtained from clinical and environmental samples showed an identity of 100% (235 nucleotides). To our knowledge, this is the first case study to directly demonstrate the presence of norovirus RNA on a food handler's hands in an outbreak setting. This finding provides direct evidence for the feasibility of transmission of norovirus by a food handler to food. Education of food handlers on the infectivity of norovirus and updating of hygienic codes are strongly recommended.