THE CONTAGIOUS stomach bug that hit more than 500 passengers on the luxury P&O liner Aurora and made them the pariahs of the Mediterranean last year has now closed three wards at Macclesfield General Hospital

The bug, known as an SRSV or Norovirus, causes projectile vomiting and diarrhoea and by Tuesday morning 57 patients and an undisclosed number of staff had been hit.

The hospital are labelling it a "viral outbreak" and say three general medical wards have been closed and a fourth affected.

They have refused to identify two nursing homes in the area that have also been hit by the bug but say one has been cleared and the other remains closed to new admissions.

Their attempts to bring it under control are being aided by Cheshire and Merseyside Health Protection Unit but with four out of eighteen wards affected there is already a major disruption in hospital activity. Outbreaks usually affect both patients and staff, sometimes with attack rates in excess of 50per cent.

The East Cheshire NHS Trust say 38 patients were affected by last Friday and the figure had risen to 57 by this Tuesday.

Medical director Dr Alan Wills has appealed to the public to limit visits to Macclesfield Hospital. He said: "If you feel at all unwell yourself, or if your visit is not absolutely necessary, please do not visit the hospital at this stage. Babies or young children could be more susceptible."

"We want people before visiting to consider if it is really necessary, for instance in a family group do the children need to come as well? And, of course, if anyone is feeling ill themselves, it would be better for them not to visit."

Patients can still visit the Accident and Emergency department and the outpatients department is not immediately affected. No operations have yet been cancelled as medical, not surgical wards are affected.

The virus is airborne, but can also be spread by hands. A ward has to be clear for 48 hours before it can be reopened. The impact on hospital beds is severe but the hospital says it is coping.

Dr Wills added: "Staff on the wards, as well as cleaning and other staff, have worked very hard over the holiday weekend to make life as comfortable as possible for patients affected by the outbreak in addition to their first illness."

The decision to reopen is made in discussions between the local infection control team and the Health Protection Agency.

Dr Nick Phin, Consultant in Communicable Disease Control with the Health Protection Authority, and the man who advised Macclesfield Borough Council over the legionella virus discovered in the town's leisure centre, said: "Most hospitals are affected by this bug at some stage."

"Unless it is dealt with appropriately you tend to see waves of infection as it comes back. That is the reason the hospital has closed wards to ensure no-one else gets infected and to give them a thorough clean."

"Once no cases have been reported for 48 hours we can look at re-opening the ward."

He estimated that the outbreak may be over in a week to ten days, although people can remain infectious for more than a week after the symptoms disappear.

The last outbreak of the bug at Macclesfield was in October 2002 and it also affected Congleton Hospital. About 80 patients were ill in the largest outbreak for four years. This time Congleton has not been affected so far.

Norovirus or SRSV is the most common cause of infectious gastroenteritis in England and Wales. Although relatively mild, the illness can occur at any age and the incubation period is usually 24 to 48 hours.

It causes vomiting, diarrhoea, fever and is transmitted from person to person by faeces, projectile vomiting and the contamination of toilets, food and water.

It can, according to the Health Protection Agency (HPA) result in severe staff shortages, particularly if several wards are involved at the same time.

They say that, by the time an outbreak has been recognised at ward level, most susceptible individuals will have been exposed to the virus.

Prompt cleaning and disinfection of areas contaminated by vomit and faeces is essential, as is hand washing after contact with affected individuals and objects, before handling food or drink, and on leaving an affected area.

The HPA says non-essential staff should be excluded from affected clinical areas and wards should be closed to admissions to prevent the introduction of further susceptible individuals.

Anyone who thinks they may be affected by the virus should watch for symptoms including vomiting, diarrhoea, and some stomach cramping, they may also suffer low-grade fever, chills, headache, muscle aches, nausea, and tiredness

You can catch the virus by eating food or drinking liquids that has been infected, touching infected surfaces or objects, being present while someone is vomiting, sharing food or eating from the same utensils while caring for a sick person, shaking hands and especially not washing hands.