Norovirus Q&A: Bah humBUG... soap is key defence against scourge of Christmas present Why should we be worried? Almost one million people have fallen victim to the bug since the summer and it is infecting around 100,000 people a week according to latest figures from the Health Protection Agency (HPA). These show there were 337 laboratory-confirmed cases in the week ending 9 December, an 83 per cent increase on the previous week. For every confirmed case it is estimated there are 288 unreported cases. This is the last update from the HPA before Christmas - the next will be published on 28 December. Does it matter? Yes - unless you think being struck down with diarrhoea and vomiting is fun at Christmas. It has already caused widespread disruption in hospitals, schools and care homes and poses a threat anywhere where people congregate. There were 61 hospital outbreaks in the two weeks to 16 December. However it is generally a mild illness - most people recover in a couple of days but in the unwell or elderly it can be more serious. Is there anything special about it? Yes - it is highly contagious. If a member of your family falls ill there is a high risk others will follow. It is transmitted by touch, contact with contaminated surfaces or consuming contaminated food or water. It is one of the few infections you really can catch from a toilet seat. The virus can travel almost 10 feet in a vomiting episode. What is the best defence? Soap. Plenty of it, used often and liberally. Soap is more effective at destroying the virus than alcohol hand gels. If you suspect someone may be infected avoid shaking hands. When handwashing is not an option, avoid touching your face or lips and giving the virus a lift to its intended destination - your small intestine. Is it only transmitted by touch? Occasionally, aerosolised particles of the virus may float in the air, raising the prospect of more distant infection. A girl's football team in Canada was laid low by the bug after a team-mate developed the illness even though she had had no contact with them. The source was traced to a grocery bag containing crisps and cookies in the bathroom the girl had used. When the team touched the bag and ate the crisps they became infected. How do you get rid of it? With difficulty. Tests suggest it can hang around on hard surfaces for up to two weeks, unless cleaned and disinfected. Its survival ability has led to its being dubbed the "ideal infectious agent." As few as 18 particles of virus can infect a new person and there may be as many as a thousand in a speck of vomit. Despite research efforts, there is no sign of a vaccine to prevent it in sight. Can it be treated? Yes - with time. Nothing else works. Take paracetamol if you have a fever or headache, drink plenty to keep yourself hydrated (not tea, coffee or alcohol, which makes you pee more), and let nature take its course.