Norovirus
A number of viruses can cause food poisoning in humans
(gastroenteritis). In Europe and other developed regions, it
is recognised that most shellfish-associated gastroenteritis
is caused by norovirus (also known as small round structured virus
(SRSV) or Norwalk-like virus).
Norovirus can be found in human sewage. If sewage contaminates
the areas in which bivalve shellfish are grown, norovirus can be
concentrated during the process of filter feeding. Consumption of
such shellfish, particularly when eaten raw, can pose a risk of
contracting gastroenteritis.
Illness associated with norovirus, also referred to as the
"winter vomiting disease":
- causes unpleasant but self-limiting sickness and diarrhoea
- usually appears 12 to 72 hours after consuming contaminated
shellfish
- lasts up to 96 hours.
Outbreaks of illness, associated with oysters or other lightly
cooked shellfish, are infrequent but can be lead to significant
negative publicity for businesses and damage to consumer
confidence.
There is currently no legal requirement for
testing shellfish for norovirus, and no published reference method.
Our norovirus testing method is derived from the proposed standard
for quantifying norovirus in foodstuffs, which is currently being
developed by a joint European Committee for Standardisation (CEN)
and International Standards Organisation (ISO) group of experts
(including Cefas virologists).
Our norovirus tests use a molecular approach that enables the
detection of a defined fragment of the viral genome. The method
used is the real-time reverse transcriptase polymerase chain
reaction (real-time RT-PCR). No other type of testing method is
appropriate for norovirus in bivalve shellfish because of the lack
of sensitivity when trying to detect the low levels of viral RNA
typically found in food.
Related publication
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