A measles alert has been issued for the Busselton area.
It is the second confirmed case this month in the region.
People who visited Vasse Coles in the afternoon or evenings of July 21, 22, 23 and 24 or Vasse McDonald's on the evening of July 24 should remain vigilant for the onset of measles symptoms.
Children and adults who are not already immune could be at risk.
Measles is a highly contagious viral illness that is spread though coughing and sneezing.
Early symptoms include fever, cough, runny nose and sore eyes, followed by a red blotchy rash three or four days later.
People who are concerned they may have measles and require medical advice after hours can contact Healthdirect on 1800 022 222.