Nine patients at Harrogate District Hospital are being treated for the 'flu' and others are being given preventative medicines after an outbreak on the Jervaulx Ward.
Staff are urging people with 'flu like symptoms' to stay away from the hospital site, and encouraging others to make sure they are vaccinated against the illness.
Dr Jenny Child, Consultant Microbiologist & Director of Infection Prevention and Control at Harrogate & District NHS Foundation Trust (HDFT), highlighted how serious the flu can be.
She said: "Jervaulx Ward at Harrogate District Hospital has been closed to new admissions after nine patients have been confirmed as having ‘flu since the evening of Thursday January 10.
"They are being treated with oseltamivir (Tamiflu). Patients in the same bays as those affected have been offered preventative treatment.
"The situation is being monitored closely and well managed by staff. The ward will remain closed until it is considered safe to re-open it.
"We ask members of the public who have loved ones in the hospital not to visit if they themselves are suffering from ‘flu-like symptoms, including a fever (high temperature) or chills, sore throat, cough or muscle aches.
"Flu can be very serious and is different to the common cold. It’s not too late to have the flu jab. Free flu vaccinations are available for pregnant women, those aged 65+, and those with underlying health conditions including diabetes. Find out more from your GP or local pharmacy."