Use of protective gloves alone does not prevent norovirus transmission


<p>Noroviruses can easily spread from a food worker's hands to foods that are consumed unheated. Unless sufficient hand hygiene is maintained, protective gloves may not necessarily prevent the transmission of the virus. Effective methods for combating norovirus outbreaks include a frequent change of gloves, the careful washing of hands and use of clean ingredients.</p>

The Finnish Food and Safety Authority Evira, the University of Helsinki and VTT Technical Research Centre of Finland used simulated conditions to study norovirus transmission from a food worker's hands to ready-to-eat foods meant to be consumed without further preparation. The study focused on the cucumber sandwich, as it has simple ingredients, and cucumber must be handled repeatedly during the preparation. As a foodstuff, cucumber itself presents a small risk.

Clean hands are the key

Norovirus is among the most common causes of gastroenteritis in adults. In 2013, it caused approximately one third of the food-transmitted epidemics in Finland. Norovirus outbreaks transmitted via food have often been linked to infected food workers or persons preparing meals.

Norovirus is easily transmitted from person to person, particularly during the illness, through faeces and vomit, but also long afterwards. A person may transmit the virus even though exhibiting no symptoms. Noroviruses can be transmitted via foodstuffs, water and a range of surfaces, such as door handles, and even fabrics.

A study was carried out to assess the effect of hand hygiene on product contamination. In test conditions, transmission was found to occur from the test person's virus-contaminated hands to the protective gloves, albeit in fairly small quantities, each time the test was repeated. The study also assessed the volume of virus transmitted to the sandwich from a cucumber whose surface was contaminated with norovirus. The protective gloves were much more effective in transmitting norovirus to the cucumber sandwich than the contaminated ingredient.

"We found that if the protective gloves contained even a small number of noroviruses beforehand, the norovirus was transmitted to the cucumber sandwich. The person's hands were more effective in spreading the virus than any single ingredient," said Researcher Maria Rönnqvist from Evira's Risk Assessment Research Unit.

The results were saved in a mathematical model developed during the study, enabling the assessment of norovirus transmission to hand-prepared foods. The model was used to assess the number of noroviruses transmitted from the hands to the sandwich relative to the virus volume detected on the person's hands before putting on protective gloves and preparing the sandwich.

Frequently asked questions regarding norovirus
Handling and storing foodstuffs

Results of the risk assessment have been published in a peer-reviewed scientific publication
Rönnqvist, M., Aho, E., Mikkelä, A., Ranta, J., Tuominen, P., Rättö, M., Maunula, L.
Norovirus Transmission between Hands, Gloves, Utensils, and Fresh Produce during Simulated Food Handling.
Applied and Environmental Microbiology 2014: Vol. 80, No. 17, pp. 5403-5410.

The project was introduced in Evira's Science Day 2014.

A completed project studying virus detection and control methods in processing environments has produced a number of publications and presentations.

Evira's risk assessment and related projects.

For further information, please contact:
Researcher Maria Rönnqvist, tel. 040 178 6623


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