Health officials today isolated nearly half of the wards in a general hospital after dozens of patients and staff contracted a vomiting virus.

The highly contagious condition, which causes diarrhoea and projectile vomiting, struck seven out of 16 wards at the Kent and Canterbury hospital.

A total of 56 patients and 33 staff were diagnosed with the norovirus - commonly known as winter vomiting disease. The patients have been grouped together and isolated from the rest of the hospital.

Friends and relatives were told to stay away and matrons, nurses and cleaners were brought in to reduce the impact of the virus, which is airborne.

Elaine Strachan-Hall, director of nursing and quality at East Kent hospitals trust, said: "This is not a life-threatening infection, but very distressing to all those who catch it, especially when they are sick already.

"It is airborne so we are asking visitors to stay away to give staff more time to concentrate on patient care."

Dr Mathi Chadrakumar, Kent and Medway's health protection agency director, said staff were working to create specially clean wards.

"We believe patients had already contracted it and were incubating it when they were admitted," he said. "Because it was brought into the hospital where staff and patients are grouped close together, it spread."

Dr Chadrakumar said the airborne virus could be contracted by one person vomiting near another, and that patients did not need to touch each other to catch it.

He said the condition should clear up after 48 hours and many of those affected had already recovered.

The norovirus is the most common cause of infectious gastroenteritis and affects around 600,000 to 1 million people in the UK each year.