Winter vomiting bug, or norovirus, is a stomach bug that causes diarrhoea and vomiting. It can be very unpleasant but usually goes away within a couple of days. The norovirus is a very infectious virus that causes vomiting and diarrhoea. Anyone can contract norovirus and become ill. Viruses are highly contagious, and they are commonly spread via contaminated food and water or through contaminated surfaces. Close contact with an infected person can also lead to infection. Vomiting, diarrhoea and stomach pain typically begin 12 to 48 hours after exposure. It usually takes one to three days for norovirus symptoms to subside, and most people recover completely without medication. It is important to note that vomiting and diarrhoea can cause severe dehydration for some people - especially infants, the elderly and people with underlying conditions. All such people might need special medical attention to help combat the virus. Norovirus infections are most common in closed and crowded environments such as hospitals, nursing homes, child care centres, schools, and cruise ships.