Esperance residents need to be alert to the risk of measles following confirmation of measles in a person who visited the region.
The patient was at the Condingup Community Centre on the evening of August 23 , the Esperance Football Ground on the morning of August 24 and the Esperance Hockey Club on the morning of August 24.
Children and adults who have been exposed are at risk of developing measles if they are not immune.
Individuals should remain vigilant for the start of measles symptoms for the next 18 days if they were at any of the above locations.
According to the WA Country Health Service's Dr Charles Douglas, measles is a serious and highly contagious viral illness that spreads when infected people cough and sneeze.
"Being in the same room around the same time as someone with measles can result in infection in people who are not immune," Dr Douglas said.
"People with measles typically develop symptoms approximately 10 to 18 days after exposure.
"Early symptoms include fever, cough, runny nose and sore eyes, followed by a red blotchy rash three or four days later.
"The rash usually starts on the face and spreads to the rest of the body."
Dr Douglas said complications following measles could be serious and include ear infections and pneumonia in about 10 per cent of cases.
"Around one in every five people will require hospital admission and about one person in every 1,000 will develop encephalitis - inflammation of the brain," he said.
The WA Country Health Service has urged parents to make sure their children receive their measles vaccinations on schedule.
The vaccine is currently administered to children at 12 and 18 months of age.
People born during or after 1966 are also asked to check they have had two documented doses of a measles vaccine at some stage in their life, especially before travelling overseas.
If they are not sure, they should see their doctor for a vaccination before leaving Australia.
Dr Douglas said each measles case was a public health emergency because of the risk of local spread - including to those most vulnerable to infection, such as infants too young to be vaccinated, pregnant women and those with compromised immune systems.
"With high vaccination coverage, naturally occurring measles has been eliminated from WA for around 20 years, but occasional cases and small outbreaks occur, sparked by residents or visitors who were infected overseas," he said.
Anyone who thinks they may have measles should call ahead to a clinic or emergency department so that they can be isolated from infecting other patients and staff when they arrive.
People who are concerned they may have measles and require medical advice after hours can contact Healthdirect on 1800 022 222.
For further information, visit the HealthyWA website.