Norovirus is mostly passed on by close contact, which is why it spreads so fast in schools and nurseries.
All 12 days of Christmas are over, the decorations are packed away and some New Year's resolutions have not only been made but broken. Now it's time for kids to go back to school, and return to classrooms and playground. The new term always brings with it a rash of coughs and colds, as kids cram into classrooms and cough or sneeze on each other. But over this new term hovers the prospect of a new surge in cases of norovirus.
Pretty much all of us have experienced the sickness and diarrhoea that infection with norovirus brings - it may only last for a couple of days in most people, but they're memorable days for all the wrong reasons. It's the most common virus causing diarrhoea and vomiting among adults in the UK. Part of the problem is that unlike some other viruses, which your body becomes immune to when you've been infected with them once, you're only immune to norovirus for about three to four months after you catch it. That means you can get it more than once in a lifetime, or even in a year.
In the average year, 600,000 to 1 million people in the UK catch norovirus. The Health Protection Agency measures figures from July to July every year, and by 1st January 2013 they estimate that over 1 million people have been affected this season - 72% higher than at this stage in the season last year. Traditionally, cases of norovirus are highest around New Year, so there may be more to come. It's mostly passed on by close contact between people, which is why it spreads so fast in schools, nurseries and hospital wards.
Although most people recover completely from norovirus within days, it can occasionally cause severe illness through dehydration. If you or your child is in one of the groups most at risk, watch out for symptoms of dehydration and see your doctor if you're concerned. Otherwise, stay away from your doctor! Norovirus can be easily passed on to other patients in the waiting room. Keeping fluid intake up is key - in the past, doctors used to recommend stopping breast or bottle milk feeding in babies, but we now recommend continuing with normal feeds, and adding extra rehydration drinks if necessary .
There are lots of simple measures that will reduce the risk of catching norovirus, but while most of them are common sense, they can be easily overlooked. While most people realise how important it is to wash their hands before cooking or eating, we may forget that norovirus germs can linger on door handles and even towels and flannels. If you are affected, don't return to work or school until at least 48 hours after your symptoms have settled. You may think you're being heroic, but you'll be doing your colleagues no favours at all.