Health authorities are urging people to watch out for measles symptoms after four people carried the disease to NSW.
Four infected travellers, including two children, travelled to NSW on flights from Cairns and from Delhi in India last week.
Two people arrived via a Virgin flight on March 28 and a Tiger Airlines flight on March 29.
One person was taken to Royal North Shore Hospital's emergency department on the night of March 29.
Two children, who most likely caught the highly infectious disease in India, travelled on flight AI302 from Delhi to Sydney on March 30.
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They visited a medical centre in Blacktown and Mt Druitt Hospital while infectious on Saturday.
NSW Health said people who hadn't been vaccinated should look out for symptoms, including fever, sore eyes, coughing and a rash spreading from the head and neck.
It said people who hadn't received two doses of measles vaccine should be alert.
"If you develop the symptoms of measles, seek medical advice," NSW Health communicable diseases director Dr Vicky Sheppeard said on Wednesday.
"Please call ahead to your doctor or emergency department so that arrangements can be made to keep you away from others to minimise the risk of infection."
