Norwalk-like
viruses are recognized as the most important cause of
non-bacterial outbreaks of gastroenteritis worldwide.
Although it is a serious problem in many countries,
this foodborne hazard could be eliminated and prevented.
Let us know more about the viruses!
Q:
What
are Norwalk-like viruses?
A:
Norwalk-like
viruses are known as Small Round Structure Viruses (SRSVs).
Gastroenteritis caused by Norwalk-like viruses is usually
mild and self-limiting. Symptoms may include nausea,
vomiting, non-bloody diarrhea, and abdominal cramps.
According to the literature, Norwalk-like viruses are
common pathogens of viral gastroenteritis, and Norwalk-like
viral gastroenteritis are more common in winter.
Q:
How
do the Norwalk-like viruses spread?
A:
The
only known host for Norwalk-like viruses is infected
human. It can be spread by fecal-oral route via contaminated
food and water. Other major modes of transmission include
person-to-person spread, contact with contaminated object
and aerosol spread.
Q:
What
foods are commonly identified as source of outbreaks?
A:
As
Norwalk-like viruses are commonly found in sewage-contaminated
water, the shellfish harvested from polluted water or
vegetables irrigated with polluted water are highly
likely to be contaminated. Therefore, ingestion of raw
or inadequately cooked foods, including shellfish, salad
and raw vegetable, poses a high risk of Norwalk-like
viruses infection. In Hong Kong, raw oysters have been
implicated in food poisoning outbreaks associated with
Norwalk viruses *. In other countries, ice, salad, raw
vegetables and raw shellfish have also been identified
as the vehicles of food poisoning outbreaks caused by
Norwalk-like viruses. Anyone who consumes food contaminated
with Norwalk-like viruses is susceptible to the infection.
Q:
How
can Norwalk-like viruses be prevented?
A:
The
key to prevention of Norwalk-like viruses infection
is strict observance of food, personal and environmental
hygiene.
Advice
to the public
The
public should patronise licensed and reputable food
premises, especially when taking high risk food like
raw oysters.
All food, in particular shellfish, should be cooked
thoroughly before consumption.
If
the vegetables are taken fresh or for salad preparation,
they must be thoroughly washed, and kept well-covered
in refrigerator at 4oC.
Hands
should be washed thoroughly with plenty of soap and
hot water after using toilet and before handling food
or eating.
Travellers
visiting places appeared to have a polluted water
supply are advised to drink pasteurized milk or bottled
beverages without ice, and take thoroughly cooked
foods while serving hot.
Advice
to trade
All
foods, especially shellfish, should be purchased from
reliable and reputable suppliers.
Importers
are strongly encouraged to obtain health certificate
issued by the health authority of country of origin
to certify the food concerned is fit for human consumption.
Food
handlers with symptoms of vomiting or diarrhoea should
not handle food until they are symptom-free for at
least two days.
*
Source: Department of Health. Public Health & Epidemiology
Bulletin. February 2000
Last
revision date: 09-07-2001