Norovirus cases exceed 1m this winter HPA figures show there have been 3,877 laboratory-confirmed cases of norovirus in Britain this winter. Photograph: Ferenczy Europress/FEB More than 1.1 million people in Britain have succumbed to the norovirus vomiting disease so far this winter, and health officials expect cases to jump higher after a dip over Christmas and the New Year. The Health Protection Agency (HPA) said cases of the highly contagious disease have risen earlier than expected this winter - a trend also seen across Europe, Japan and other parts of the world. Health officials in the US said last week that more than 400 people on two cruise ships had been taken ill with a sickness suspected of being due to the norovirus, and hospital wards and nursing care homes in Europe had been forced to close to try to stop infections spreading. Norovirus is transmitted by contact with infected people or contaminated surfaces, food or water. HPA data released on Wednesday revealed there have been 3,877 laboratory-confirmed cases of norovirus in Britain this winter, 72% higher than the number of cases reported at the same point last year. The reason for the rise in not known. For every laboratory-confirmed case, scientists estimate there to be 288 unreported cases, as the vast majority of those affected don't go to a doctor. "As we have seen in previous years, there has been a dip in the number of confirmed laboratory reports owing to the Christmas and New Year period," said John Harris, the HPA's norovirus expert. But he added that the HPA expected to see a rise in the number of laboratory reports in the next few weeks. Norovirus symptoms include a sudden onset of vomiting and diarrhoea. Some victims also suffer fevers, headaches and stomach cramps. "If you think you may have the illness then it is important to maintain good hand hygiene to help prevent it spreading," said Harris. We also advise that people stay away from hospitals, schools and care homes as these environments are particularly prone to outbreaks.