Also known as 'winter vomiting virus', 'small round structured
virus' or 'Norwalk-like virus'
Question 1: What are Noroviruses?
Noroviruses are a group of viruses that are the most common
cause of gastroenteritis (stomach bugs) in England and Wales. In
the past, noroviruses have also been called 'winter vomiting
viruses', 'small round structured viruses' or 'Norwalk-like
Question 2: How does Norovirus spread?
The virus is easily transmitted from one person to another. It
can be transmitted by contact with an infected person; by consuming
contaminated food or water or by contact with contaminated surfaces
Question 3: What are the symptoms?
The symptoms of norovirus infection will begin around 12 to 48
hours after becoming infected. The illness is self-limiting and the
symptoms will last for 12 to 60 hours. They will start with the
sudden onset of nausea followed by projectile vomiting and watery
diarrhoea. Some people may have a raised temperature, headaches and
aching limbs. Most people make a full recovery within 1-2 days,
however some people (usually the very young or elderly) may become
very dehydrated and require hospital treatment.
Question 4: Why does Norovirus often cause outbreaks?
Norovirus often causes outbreaks because it is easily spread
from one person to another and the virus is able to survive in the
environment for many days. Because there are many different strains
of Norovirus, and immunity is short-lived, outbreaks tend to affect
more than 50% of susceptible people. Outbreaks usually tend to
affect people who are in semi-closed environments such as
hospitals, nursing homes, schools and on cruise ships.
Question 5: How can these outbreaks be stopped?
Outbreaks can be difficult to control and long-lasting because
norovirus is easily transmitted from one person to another and the
virus can survive in the environment. The most effective way to
respond to an outbreak is to disinfect contaminated areas, to
institute good hygiene measures including hand-washing and to
provide advice on food handling. Those who have been infected
should be isolated for up to 48 hours after their symptoms have
Question 6: How is norovirus treated?
There is no specific treatment for norovirus apart from letting
the illness run its course. It is important to drink plenty of
fluids to prevent dehydration.
Question 7: If I'm suffering from norovirus, how can I prevent others from becoming infected?
Good hygiene is important in preventing others from becoming
infected - this includes thorough hand washing before and after
contact. Food preparation should also be avoided until 3 days after
symptoms have gone altogether.
Question 8: Who is at risk of getting norovirus?
There is no one specific group who are at risk
of contracting norovirus - it affects people of all ages. The very
young and elderly should take extra care if infected, as
dehydration is more common in these age groups.
Outbreaks of norovirus are reported frequently
in semi-closed institutions such as hospitals, schools, residential
and nursing homes and hotels. Anywhere that large numbers of people
congregate for periods of several days provides an ideal
environment for the spread of the disease. Healthcare settings tend
to be particularly affected by outbreaks of norovirus. A recent
study done by the Agency shows that outbreaks are shortened when
control measures at healthcare settings are implemented quickly,
such as closing wards to new admissions within 4 days of the
beginning of the outbreak and implementing strict hygiene
Question 9: How common is Norovirus?
Norovirus is not a notifiable disease so reporting is done on a
voluntary basis. The HPA only receives reports of outbreaks and we
see anywhere between 130 and 250 outbreaks each year. It is
estimated that Norovirus affects between 600,000 and a million
people in the UK each year.
Question 10: Are there any long-term effects?
No, there are no long-term effects from Norovirus.
Question 11: What can be done to prevent infection?
It is impossible to prevent infection, however, taking good
hygiene measures (such as frequent hand washing) around someone who
is infected is important. Certain measures can be taken in the
event of an outbreak, including the implementation of basic hygiene
and food handling measures and prompt disinfection of contaminated
areas, and the isolation of those infected for 48 hours after their
symptoms have ceased.