Study reveals food handlers contributed to norovirus outbreaks

The role of infected food handlers in two norovirus outbreaks in Spain has been highlighted recently by researchers.

Two gastroenteritis outbreaks occurred a week apart in the same facility in Lleida, Spain, in 2018. The most frequent symptoms were abdominal pain, vomiting, and nausea.

The first outbreak was associated with salad consumption and the second with a cheese omelet.

Norovirus was detected by RT-PCR and sequenced in both groups of students and in the food handlers who prepared the meals, found the study published in the journal Scientific Reports.

First outbreak details
In April 2018, the Epidemiological Surveillance Service of Lleida, Alt Pirineu, and Aran received a report of a possible outbreak of acute gastroenteritis in a group of students from a high school in Lleida who had attended a holiday camp house. A week later, a second outbreak was reported at the same facility, affecting another group from the same school. 

The first outbreak with 19 patients was reported two days after arriving at the site. The second outbreak was reported with 12 cases. There were two food handlers in charge at the camp house.

In the first outbreak, 29 surveys of the 32 group members were analyzed, and 26 people were sick. The students were 12 and 13 years old, and three teachers were between 43 and 53.

Fixing the exposure point at the salad consumption, the incubation period of 22 cases was calculated with a median of 31 hours and a range of 27 to 46 hours. The virological analysis detected Norovirus in five fecal samples from patients.  Analysis of a sample of the salad was carried out with negative results.

The first handler had acute gastroenteritis symptoms the day before the arrival of the first school group, and the second handler the day after their arrival. Fecal samples from both of them were negative.

Second outbreak findings
In the second outbreak, 23 surveys were analyzed, and 16 people were sick. The age of respondents was 12 and 13.

Placing the source of exposure at the consumption of omelet, the incubation period of 15 patients was a median of 28 hours with a range of 16 to 49 hours. Norovirus was found in four stool samples from patients. Analysis of the cheese omelet was not possible.

Fecal samples from both food handlers were now positive for norovirus. In the inspection after the second outbreak, as in the previous visit, sinks in the toilets and handwashing points in the kitchen had not been equipped with soap dispensers and paper towels. Not following guidelines for disinfectant to be used to clean surfaces was also observed, and a company was asked to come in and disinfect the kitchen and toilets.

To avoid successive outbreaks in the same facility, food handlers with symptoms of gastroenteritis should not go to work for up to 48 hours after resolution of symptoms, said researchers.

“It is also necessary to make adequate devices for proper handwashing (soap dispensers and hand dryers) available everywhere. These results highlight the importance of exclusion from work of food handlers with gastroenteritis, the adequate availability of mechanisms for correct handwashing and the correct cleaning of surfaces,” they added.

(To sign up for a free subscription to Food Safety News, click here.)