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 a person 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 one to two days, however 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 fifty percent 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.

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 ceased.

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 three days after symptoms have gone altogether.

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 four 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 only receives reports of outbreaks and we see 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.

Are there any long-term effects?
No, there are no long-term effects from norovirus.

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.

Source: Health Protection Agency, an umbrella authority set up in 2003 to connect government public health authorities and organisations.

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