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 viruses’.
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 or objects.
What are the symptoms?
The symptoms of norovirus infection will begin around 12 to 48 hours after the patient
becomes 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, but some people (usually the very young or
elderly) may become very dehydrated and require hospital treatment.
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 cruise ships.
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 (alcohol hand gel is not effective against norovirus) and
to provide advice on food handling. Those who have been infected should be isolated for a
minimum of 48 hours after their symptoms have ceased. Affected members of staff should be
excluded from work until they have been free from symptoms for 48 hours.
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.
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 48 hours after symptoms have completely resolved.
Who is at risk of getting norovirus?
No specific group is at risk of contracting norovirus infection. 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.
Norovirus outbreaks 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 HPA study shows that outbreaks are shortened when control measures in 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 measures.
How common is norovirus?
Norovirus is not a notifiable disease so reporting is done on a voluntary basis. The HPA
receives reports of outbreaks and we see between 130 and 250 of these each year. It is
estimated that norovirus affects between 600,000 and a million people in the UK each year.
Are there any long-term effects?
There are no long-term effects from norovirus.
What can be done to prevent infection?
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; the isolation of those infected and the exclusion of affected staff
members until 48 hours after their symptoms have ceased.
Available online at: http://www.hpa.org.uk/Topics/InfectiousDiseases/InfectionsAZ/Norovirus/