Norovirus can easily be spread from person to person in the workplace, said Dr Paul Cooke, head of microbiological food safety at the Food Standards Agency (FSA). While those suffering from norovirus should be free of symptoms for 48 hours before returning to work, the virus can still be infectious for some time, even without symptoms, Cooke warned.

The danger is greatest with products that do not require further heating or cooking by consumers, said Cooke, which is why worker and factory hygiene are so crucial.

Faecal Matter

Norovirus cannot be cultured in laboratories, so firms use an ‘equivalent’ virus when testing the effectiveness of sanitisers, said Dr Angus Knight, principal consultant in microbiology at Leatherhead Food Research. However, in its natural state, norovirus grows in a “faecal matrix” and is much hardier than its laboratory-grown equivalents, he said. Test results can make a cleanser look more effective than it actually is, he added. “If something lives in poo, it’s probably going to be able to survive.”

Meanwhile, food scientists also struggle to know the extent to which products are contaminated with norovirus. Because it cannot be grown in culture in a laboratory, it is detected by molecular testing for genetic particles, said Cooke.

Current molecular tests are too sensitive to tell active viral particles from dead ones, said Knight.