Thousands of Britons struck by vomiting virus

Thousands of people in Britain have been sickened by the biggest outbreak of a winter vomiting virus in five years.

Doctors estimate that hundreds of thousands of people may be affected by norovirus in the coming days. Dozens of hospital wards across the country have already been closed to try to stop the virus' spread.

"General practitioners are seeing a huge number of cases of patients with the norovirus," said Steve Field, chairman of the Royal College of General Practitioners.

Norovirus is the most common stomach bug in the United Kingdom, and its incidence typically spikes during the winter.

"The norovirus season has started uncharacteristically early compared to other years," said the Health Protection Agency in a statement. Most cases go unreported, and the agency estimates that for every case, there are 1,500 others.

The virus is highly contagious, and is easily transmitted between people via contact with contaminated surfaces, or sharing contaminated food or water.

Symptoms include nausea, projectile vomiting, diarrhea, fever and muscle pain. Most people recover within two days without treatment, though the virus can be more serious in the very young or the elderly.

People struck by the virus are advised to stay at home, drink plenty of liquids, and to wash their hands regularly to prevent infecting others.

The Health Protection Agency estimates that there are between 600,000 and 1 million cases of norovirus in the U.K. every year. Numbers of cases vary every year, and the agency said that this year's figures are not yet exceptional.