Norovirus was the main cause of outbreaks and related illnesses, according to a Dutch study including 12 years of data.

Researchers studied foodborne outbreaks between 2006 and 2019 in the Netherlands to guide efforts to control, reduce and prevent future illness.

In total, 5,657 foodborne outbreaks with 27,711 cases were identified. An average of 404, ranging from 206 to 756, outbreaks with 1,979 cases were reported each year. The largest incident affected 1,149 people. The pathogen causing disease remained unknown in almost 90 percent of outbreaks.

A contaminated food product was confirmed in 152 outbreaks while in 514 incidents, a pathogen was detected in cases and/or environmental swabs, according to the study published in the journal Eurosurveillance.

Norovirus caused the most with more than 200 and had the most related cases, followed by Salmonella and Campylobacter. Many norovirus outbreaks were identified by positive environmental swabs, supported by confirmation in cases or reported symptoms pointed toward the virus.

Bacillus cereus was most often found in outbreaks with a confirmed food vehicle while 21 of 27 norovirus outbreaks were related to shellfish.

Salmonella outbreaks with a confirmed source were mostly related to red meat, eggs, poultry meat and dairy with Campylobacter outbreaks traced to raw milk or raw milk cheese and poultry.

Setting and food product
Contamination during the production process, consumption of raw products, and improper hygiene, handling, storage and preparation are underlying factors that could be addressed to reduce the number of outbreaks, said researchers.

The three largest outbreaks were caused by Salmonella: in 2012 from Salmonella Thompson in smoked salmon with 1,149 reported cases, in 2006 from Salmonella Typhimurium in cheese with 224 cases and in 2008 from Salmonella Enteritidis with 195 cases, most likely due to eggs.

Shiga toxin-producing E. coli (STEC) and Listeria both caused 11 outbreaks while hepatitis A virus was linked to 10.

Salmonella outbreaks are being seen less with between six and 15  from 2014 to 2019, compared with between 15 and 22 outbreaks per year in 2006 to 2012. Campylobacter outbreaks also have been less reported since 2014 compared with 2006 to 2013.

Public eating places such as restaurants, delis and cafeterias were most often mentioned as a setting where food implicated in an outbreak was prepared, followed by at a plant or facility and in private homes. More than 70 outbreaks involved people infected abroad.

Red meat and mixed products were the top contaminated food products. Pathogens mainly identified in outbreaks caused by composite products and red meat were Bacillus cereus, Clostridium perfringens, and Staphylococcus aureus. Other common pathogen and food pairs were Campylobacter in dairy, Salmonella in red meat, Salmonella Enteritidis in eggs, hepatitis A in fruit and vegetables, norovirus in shellfish, and scombroid toxin in fish.

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