Norovirus in Food: Why Regular Testing Matters

Norovirus in Food: Why Regular Testing Matters

A product recall issued by the Swiss Federal Food Safety and Veterinary Office (FSVO) at the end of July 2026 once again highlighted that food can become contaminated with norovirus despite high quality and hygiene standards. Certain batches of a frozen organic berry mix were affected and were withdrawn from sale as a precautionary measure.

But what exactly is norovirus, why is it so contagious, and what does this mean for food producers?

What is norovirus?

Noroviruses are among the most common causes of gastrointestinal illness. Typical symptoms include sudden onset of diarrhoea, vomiting, nausea and abdominal cramps. An infection can be particularly challenging for children, older adults and people with weakened immune systems.

In Switzerland, an estimated 400,000 people develop gastrointestinal illness caused by norovirus each year. Noroviruses are therefore responsible for a significant proportion of non-bacterial gastrointestinal infections.

What makes norovirus so contagious?

Norovirus can be transmitted through contaminated food or water, but direct person-to-person transmission and contact with contaminated surfaces are also possible.

One of the main reasons for its high transmissibility is the extremely low infectious dose: as few as 10 to 100 virus particles may be sufficient to cause illness.

In addition, noroviruses are highly resistant. They can survive freezing as well as many commonly used cleaning agents and disinfectants, and can remain infectious on surfaces for several weeks, even after drying. This combination of a low infectious dose and high environmental stability makes norovirus one of the most contagious pathogens.

Norovirus infections also show a distinct seasonal pattern, occurring more frequently during the colder months between October and March. This is thought to be partly due to people having closer contact with one another during the colder season and to the greater stability of noroviruses at lower temperatures.

Which foods require particular attention?

There is an increased risk of norovirus transmission through foods such as frozen berries, leafy vegetables, shellfish and other products that are consumed raw or are not sufficiently heated.
To reliably inactivate norovirus in food, these products should be heated to a core temperature of 90 °C for at least two minutes. Alternatively, they can be briefly brought to the boil at 100 °C.

What does the detection of norovirus mean for food producers?

Norovirus poses a significant risk in the food sector, as a single contaminated product can potentially infect a large number of people. If contamination is detected, product recalls and additional protective measures are often unavoidable.

Regular testing as part of a company’s hygiene concept and internal quality control procedures can help identify potential risks at an early stage, reduce the risk of product recalls and contribute to maintaining a high level of food safety.

How is norovirus detected?

Today, norovirus is detected using molecular biological methods such as real-time PCR. This method enables the rapid and reliable qualitative detection of norovirus in food, water and environmental samples.

Targeted laboratory testing supports food manufacturers, producers, importers and authorities in identifying potential contamination at an early stage, taking appropriate action quickly in suspected cases and helping to ensure product safety.

How can Biolytix AG support you?

We offer norovirus testing both for routine monitoring and for the investigation of specific suspected cases. For importers and food manufacturers, we can test food batches for norovirus, supporting internal quality control and quality assurance processes.

In suspected cases, our express testing services enable rapid analytical investigation. In addition to food and water samples, we can analyse swab and contact samples taken from surfaces. As part of traceability investigations, these analyses can help identify or rule out potential sources of contamination or infection.

We also support restaurants, commercial and institutional kitchens, and catering facilities – for example in schools and care homes – in investigating the potential causes of foodborne illness.

In addition to norovirus, we analyse a range of other relevant pathogenic and microbiological parameters, including:

• E. coli
• EHEC/STEC/VTEC
• Enterobacteriaceae
• Salmonella
• Campylobacter
• Listeria
• coagulase-positive staphylococci
• Bacillus cereus

In this way, we support our customers in the timely analytical investigation of potential causes and sources of contamination.

Further Information

Bundesamt für Lebensmittelsicherheit und Veterinärwesen (BLV): Öffentliche Warnung – Noroviren in Beerenmischung tiefgefroren https://www.blv.admin.ch/de/newnsb/F880wt7ttea28QG0eJI5b

Bundesamt für Gesundheit (BAG): Informationen zu Noroviren
https://www.bag.admin.ch/de/norovirus-de

SRF News: Rückruf von Lidl – Noroviren in Tiefkühl-Beerenmischung entdeckt
https://www.srf.ch/news/schweiz/rueckruf-von-lidl-noroviren-in-tiefkuehl-beerenmischung-entdeckt