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Asymptomatic food handlers common cause of foodborne illness outbreaks
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Nearly one-quarter of foodborne illness outbreaks from 2005 to 2011 were caused by asymptomatic food handlers, according to researchers from the Statens Serum Institut in Copenhagen, Denmark.
“Symptoms compatible with norovirus infection among household members, especially children, of food handlers should be taken into account, as mechanical transfer of virus particles from private homes to industrial kitchens appears to be an important cause of outbreaks,” the researchers wrote in The Journal of Infectious Diseases. “Existing guidelines recommend exclusion of symptomatic and post-symptomatic food handlers and strict hand hygiene, when household members are ill with gastroenteritis.”
The researchers reviewed 191 reported foodborne norovirus and sapovirus outbreaks that occurred from 2005 to 2011 in Denmark. They classified the outbreaks into five groups according to contamination source: asymptomatic food handlers, symptomatic food handlers, production, guests and unsolved. Asymptomatic food handlers were further classified as post-symptomatic food handlers, pre-symptomatic food handlers and gastroenteritis in food handlers’ household.
The study included 191 outbreaks comprising 6,991 recorded illnesses. Sixty-four of these outbreaks (34%) were caused by food handlers, and among those, 41 of the outbreaks (64%) were caused by asymptomatic food handlers. Half of the asymptomatic food handlers had household members with gastroenteritis, and the food handlers had no symptoms before or after preparing the food. Nine of the outbreaks were caused by pre-symptomatic food handlers and 11 were caused by post-symptomatic food handlers.
“Shedding by pre- or non-symptomatic food handlers may be difficult to prevent as no warning signs are available,” the researchers wrote. “This makes general hygienic precautions very important, such as thorough hand hygiene and use of gloves and protective clothing in kitchen areas. Exclusion of food handlers with gastroenteritis among household members could be considered.”
Disclosure: The researchers report no relevant financial disclosures.
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