THREE wards at Huddersfield Royal Infirmary have been closed to new patients because of a bug.
Admissions into and transfers out of Ward 1, Ward 7 and the medical assessment unit have been stopped because of the gastroenteritis virus known as winter vomiting disease.
However, today the the medical assessment unit, which assesses patients when they are referred to the Infirmary either by their doctor or the hospital's own accident and emergency unit, were able to re-open half of their unit.
Ward 7 cares for elderly people, Ward 1 is a vascular and medical ward.
The head infection control nurse for the Calderdale and Huddersfield NHS Trust, Carole Hallam, said: "Many people don't realise that diarrhoea and vomiting symptoms are often viral gastroenteritis.
"Although the symptoms are short-lived they can be very unpleasant and have a huge impact on hospital activities.
"Large outbreaks often result from people bringing the virus into the hospital in winter months.
"This leads, at worst, to staff shortages and restricted admissions to affected wards."
Outbreaks during winter months are common and affect nurseries, schools, care home and hospitals - as well as families.
Symptoms include nausea, vomiting, diarrhoea, headache and stomach pains.
A spokeswoman for the trust issued this advice to people:
* Don't visit friends or family in hospital or go to outpatient appointments if you have symptoms of viral gastro-enteritis or have been in contact with someone with symptoms.
* Remember that if you have had the symptoms, you will still be infectious for up to two days after they stop.
* When visiting patients in hospital always use the alcohol gel when entering and leaving the ward.
* Most wards will discourage more than two visitors per patient. Visitors should use the seats provided and not sit on beds.
* When visiting people in hospital avoid bringing in unwrapped sweets and biscuits. If you need to bring in biscuits and sweets, make sure they are individually wrapped or in airtight plastic containers.