The WA Health Department has warned doctors to be on the alert for measles after two new cases of the highly infectious disease were detected this month.

Two new cases have been identified in children from non-vaccinating families, sparking concerns that a number of other people could have been exposed to the virus in both Perth and rural parts of WA.

It is understood the children were exposed to the disease through contact with a returned traveller, who contracted the virus overseas and was treated at the Midland Health Campus earlier this month.

WA Health Communicable Disease Physician Dr Donna Mak said it was a timely reminder for families to ensure their immunisations are up-to-date, particularly during the holiday season when more people make travel plans.

"The measles vaccination is safe and highly effective," Dr Mak said.

"Children who are too young to receive the vaccination can still be protected from measles if their family members are fully vaccinated and they stay away from people who are not vaccinated."

Early symptoms of measles include a fever, cough, runny nose and sore eyes, followed by a red blotchy rash about three days later.

The rash usually starts on the face and spreads to the rest of the body.

Infections can be severe in infants and people with poor immune systems.

WA lags on Aboriginal vaccination rates

Meanwhile, a new report has found WA is lagging behind the rest of the nation in its immunisation rates for Aboriginal infants and toddlers, 15 per cent of whom are not fully immunised.

Despite improvements in recent years, WA's immunisation rate for Aboriginal infants and toddlers is as much as 10 per cent behind the leading jurisdictions.

But the state's overall immunisation rate is above the 90 per cent national target and has improved by 1.15 per cent in the past three years.

The number of children not fully immunised due to their parents' conscientious objections has also declined to less than 1.5 per cent of the state's population.

The statistics, detailed in a report by auditor general Colin Murphy, showed immunisation rates for Aboriginal children had improved across most regions in the past year.

But Mr Murphy found more work needed to be done to address the discrepancy between the Indigenous and non-Indigenous population.

The report also showed immunisation rates were much higher in regional WA than they were in the metropolitan area, with as many as one in four children in some parts of Perth not immunised.

Mundaring was identified as having the lowest metropolitan immunisation rate, at 74 per cent, while the Cottesloe-Peppermint Grove area sat at 75 per cent.