Norovirus cases may have passed 1m The HPA believes there are 288 norovirus cases for every one that is reported. Photograph: CDC/Phanie/Rex Features The number of people affected by an outbreak of the winter vomiting bug could have passed 1 million, new figures show. The number of laboratory-confirmed cases of the norovirus has reached 3,538 in England and Wales, up from 3,046 last week and an 83% increase on the 1,934 cases at this time last year, the Health Protection Agency (HPA) said. But the HPA has said that for every reported case an estimated 288 go unreported, meaning there could be 1.01 million cases, up from just under 880,000 last week. The HPA said that in the two weeks to 23 December there were 70 reported hospital outbreaks of the virus, compared to 61 in the previous fortnight, bringing the total of outbreaks for the season to 538. The number of cases has risen earlier than expected this year, following an as-yet-unexplained trend seen across Europe and other parts of the world. John Harris, an HPA norovirus expert, said: "The number of laboratory confirmed cases has risen once again as it appears that we have seen the rise in cases that usually begins in January start a little earlier than we normally expect. Norovirus is very contagious, and very unpleasant. To help prevent spread of the disease, it's important that people who believe they are unwell with the virus maintain good hand hygiene and stay away from hospitals, schools and care homes, as these closed environments are particularly prone to outbreaks which can cause severe disruption.