Mine workers in Western Australia's Pilbara region may have been exposed to measles.
A Fortescue Metals Group employee at the Christmas Creek mine site has been diagnosed.
Workers at the Cloudbreak mine who sleep on October 2 may have been exposed as well.
Measles cases in WA keep being traced back to a person who visited the Rockingham area from New Zealand.
Fortescue employees are taking no chances, with many flying back to Perth on Tuesday wearing surgical masks as a precautionary measure.
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In a statement, the company said the worker was quarantined before being transported to the hospital by the Royal Flying Doctor Service.
There have now been 22 confirmed measles cases in WA since September 30.
The total number of cases in WA this year so far has reached 48, compared to 26 over the same period last year.
Health authorities are advising people to make sure their vaccinations are up to date.