Measles Warning Issued For NSW

A measles alert has been issued for NSW after a visitor from the ACT was diagnosed with the infection.

The ACT resident was infectious while visiting the Central Coast and Sydney's northern suburbs between December 26 and 30, NSW Health said in a statement on Wednesday.

The person visited Thornleigh McDonald's, Jasmine Cafe at Umina Beach and made several visits to Deepwater Plaza in Woy Woy and Umina Beach Shopping Centre.

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Communicable diseases director Vicky Sheppeard says anyone in those locations at the same time should watch for symptoms.

"The time from exposure to the disease to the onset of symptoms is typically about 10 days but can be as long as 18 days so people should be alert to symptoms until mid-January," Dr Sheppeard said in a statement.

The infection is highly contagious and can spread through coughing or sneezing.

Measles symptoms include fever, sore eyes and a cough followed three or four days later by a red, blotchy rash spreading from the head and neck to the rest of the body.

Infants under 12 months, who are too young to be vaccinated, and young adults are most likely to be susceptible to the infection, Dr Sheppeard said.