HEALTH officials in Huddersfield are investigating an outbreak of measles.
The outbreak centres on Shepley First School - and a teacher has been detained in hospital.
Now Calderdale and Kirklees Health Protection Team is investigating a total of four people who have had symptoms which could have been caused by the measles virus.
The woman teacher, who has not been named, is being treated in Huddersfield Royal Infirmary.
Laboratory tests are being carried out to confirm whether the illnesses were caused by measles.
GPs across the town have also been contacted and asked to be alert for possible measles cases.
Three of the possible cases are connected to the school, with two children also hit by the illness.
Letters have been sent out to all parents at the school.
A spokesperson for Kirklees Education said: "Parents with children at Shepley First School have been contacted and advised of suspected cases of measles so that they can be vigilant for symptoms.
"Those with children at the school who have not been immunised are being advised to contact their GP."
Dr Howard Barnes, consultant in Communicable Disease Control for the Health Protection Agency in Huddersfield, said: "Measles is now rare in this country because of the immunisation programme.
"However, it is important to remember that measles can be a very serious illness which can have severe complications and, in very extreme cases, can even lead to fatalities.
"Children are best protected from the measles virus when they have been given two doses of the MMR vaccination.
"I would remind all parents of the importance of immunisations, to protect both individuals and our whole community from the spread of infections.
He added: "Any parent who is concerned that their child may not be protected in this way can contact their health visitor or family doctor.
"They will be able to check that the child's immunisation record is up to date and arrange for any missing vaccinations to be carried out."
Dr Sohail Bhatti, director of public health for Central Huddersfield and South Huddersfield Primary Care Trust, said he had used the Annual Health Report for Huddersfield to warn of the danger of measles, mumps and rubella returning to modern society if effective levels of immunity are not maintained in the whole population.
"We need to take urgent action to raise awareness of the devastating effects of these illnesses and encourage parents to have their children vaccinated," he said.
In the area covered by South Huddersfield PCT, 88.6% of children are being MMR vaccinated.
Health Protection Agency experts believe a rate of 95% is needed to be effective in eliminating the risk of an epidemic.
MEASLES symptoms include:
* A runny nose.
* Red eyes.
* A hacking cough.
* An increasing fever.
* A flat red or brown, blotchy rash usually starts about four days after the first symptoms, then it spreads over the face, neck and body and lasts for four to seven days.
Anyone whose child is ill and who is worried about their symptoms should contact their GP.
More information and advice about measles or the MMR vaccine is available by calling the 24-hour telephone helpline NHS Direct on 0845 4647.