HPA update on seasonal norovirus activity

Figures from the Health Protection Agency (HPA) show that there were 337 confirmed laboratory reports of norovirus in the week ending 9 December and 236 for the week ending 2 December. The latest weekly report is published today.

In this season to date there have been 3,046 confirmed laboratory reports of norovirus. This is 83 per cent higher than the same period in the last season when there were 1,669 cases reported.

The figures for the number of hospital outbreaks show that there were 61 hospital outbreaks during the last two weeks up to 16 December. In same fortnight in the previous year there were 35 outbreaks reported by the same time.

The data show that the increase in norovirus laboratory reports is earlier this season than in previous years; however, there are no indications as to why this is the case.
In the same weeks in 2011/2012 there were 257 laboratory reports and during the 2009/2010 season, which saw a lot more activity than in previous years when there were 469. In this year the majority of the cases occurred in January onwards. No two years of norovirus activity are alike and these figures represent a small fraction of the number of confirmed cases that are seen during the peak months, which usually occur between January and April.

Laboratory confirmed reports represent only a small proportion of the actual amount of norovirus activity in the community, because the vast majority of affected people do not access health care services as a result of their illness. It has been estimated that for every confirmed case there are around 288 unreported cases.

Norovirus is highly contagious and can be transmitted by contact with an infected person; by contact with contaminated surfaces or objects or by consuming contaminated food or water. The virus spreads rapidly in closed environments such as hospitals, schools and care homes.

Symptoms of norovirus include a sudden onset of vomiting and/or diarrhoea. Some people may have a temperature, headache and stomach cramps. The illness usually resolves in one or two days and there are no long-term effects.

John Harris, an expert in norovirus at the HPA, said: “The number of laboratory confirmed cases has risen again, following the drop in the number we reported last week. This is typical of the norovirus season where the number of laboratory reports fluctuates between October and April with the bulk of cases usually occurring between January and March.

“Norovirus is very contagious so we would urge anyone who thinks they may be unwell with norovirus to stay at home and stay away from hospitals and care homes.
“The infection is short-lived although it is very unpleasant while you are unwell. Most people will not need to go to see their doctor and will recover in a couple of days. It is important to take plenty of fluids to avoid dehydration.”

Advice for the public when managing a bout of norovirus:

• Do not visit your GP surgery or local A&E Unit. Norovirus infection is a self-limiting illness and you will recover naturally without treatment. It is, however, important to take plenty of drinks to replace lost fluids.
• Use NHS Direct's new diarrhoea and vomiting online health and symptom checker, to get advice on how to manage your symptoms at home or help to access the most appropriate health service https://www.nhsdirect.nhs.uk/CheckSymptoms/SATs/DandV5AndOver.aspx
• Wash hands thoroughly and regularly at all times, but particularly after using the toilet and before eating.
• Do not visit friends or relatives in hospitals or residential care homes as there is a real risk that you would introduce the infection putting vulnerable people at risk.