BIRMINGHAM, England, Dec. 15 (UPI) -- There's been a spike recently in the number of people in Britain falling ill with the stomach bug norovirus, health officials say.
The BBC reported Saturday outbreaks have been recorded at Birmingham's City Hospital, Maidstone Hospital in Kent and George Eliot Hospital in Nuneaton. In addition, more than 400 virus-infected passengers got off a cruise ship at Southampton.
The Health Protection Agency says it doesn't know the reason for the jump to 2,630 confirmed laboratory reports of the highly contagious illness from 1,533 in the same period last year.
"There are no indications as to why activity is higher this year," the agency said, adding, "It has been estimated that for every confirmed case there are around 288 unreported cases."
Agency experts say it is normal to see a series of sharp rises and falls in norovirus activity between October and April, with most falling between January and March.
Most people who fall victim to norovirus can expect to experience vomiting, diarrhea, fever, headaches and stomach cramps for a day or two.