Although food handlers are often implicated as the source of infection
in outbreaks of
food-borne viral gastroenteritis, little is known about the
timing of infectivity in relation to illness.
We investigated a gastroenteritis outbreak among employees of a manufacturing
company and
found an association (RR=14·1, 95% CI=2·0–97·3)
between disease and eating sandwiches
prepared by 6 food handlers, 1 of whom reported gastroenteritis which had
subsided 4 days
earlier. Norwalk-like viruses were detected by electron microscopy or reverse
transcriptase-polymerase chain reaction (RT-PCR) in stool specimens from several company
employees, the
sick food handler whose specimen was obtained 10 days after resolution
of illness, and an
asymptomatic food handler. All RT-PCR product sequences were identical,
suggesting a
common source of infection. These data support observations from recent
volunteer studies
that current recommendations to exclude food handlers from work for 48–72
h after recovery
from illness may not always prevent transmission of Norwalk-like viruses
because virus can be
shed up to 10 days after illness or while exhibiting no symptoms.