A woman who returned to Sydney after travelling in south-east Asia has been diagnosed with measles, as health authorities warn people who frequented the same areas to be on alert for symptoms which may take 18 days to appear.

Between the period from 29th of April to 6th of May, the woman visited Capitol Square and World Square and travelled on public transport between Town Hall and Artarmon stations in the Sydney area.

NSW Health Director of communicable diseases Vicky Sheppeard advised people who frequented those locations to be on alert until the 24th of May for measles symptoms, which can include fever, sore eyes, a cough, and a spotty rash spreading from the head to the body after several days.

If you were in those locations at those times and are highly susceptible to measles, you can contact your local public health unit on 1300 066 055.