Patients, visitors and staff at the hospital may have been exposed

Health officials issued the alert after a male member of staff at the University Hospital of North Durham tested positive for the virus.

It is feared he could have spread the bug between 13 and 17 March.

Although rare, measles is easily spread through normal contact and can be serious for children, pregnant women and those with weak immune systems.

The County Durham and Darlington Acute Hospitals NHS Trust said the staff member involved did not work in obstetrics, gynaecology, or paediatric departments.

Raised temperature

Bob Aitken, medical director at the trust, said: "Although unfortunately some people may already have been infected with measles while visiting the hospital this month, we want to minimise the chances of the infection being passed to anyone else.

"We would urge members of the public to be vigilant for the signs of this illness so that they can seek advice from their GP by telephone."

It usually takes about two weeks from catching measles to becoming ill.

Early symptoms include raised temperature, a cough and red and watery eyes. Spots associated with measles normally appear a few days later on the neck or hairline.

A Trust spokesman said: "If people show these symptoms they should not attend their GP surgery, GP walk-in centre, or hospital A&E unit, as measles is easily spread to others at this stage.

"If someone is very unwell, they can of course attend A&E, but is important that on arrival they mention they have a rash and have possibly had contact with a case of measles."