Illawarra's public health director Curtis Gregory has urged residents travelling overseas - especially to New Zealand - to ensure they're fully vaccinated against measles.
The warning comes as another measles case has been identified in someone returning from Queenstown in New Zealand's South Island.
The young man from Sydney is the third measles case in NSW in as many weeks linked to Queenstown. He is believed to have been infectious on his return Virgins Airlines flight VA162 to Sydney airport on Saturday August 31, and he then visited Northern Beaches Hospital Medical Centre on three occasions.
New Zealand is currently experiencing a widespread outbreak of measles with over 1100 cases notified this year, particularly from Auckland but also including 15 recent cases in Queenstown and nearby snowfields.
Cases are rising in Australia, and in NSW there's been 45 cases so far this year - compared to 19 for the whole of 2018. There hasn't been a notified case in the Illawarra Shoalhaven Local Health District since 2017, but Mr Gregory said it was important to be prepared given outbreaks elsewhere.
"What we're seeing in Australia is cases that are coming from overseas, or related to cases from overseas," he said.
"In New Zealand for instance, there's been a dip in vaccination coverage which has resulted in pockets of unvaccinated people - and because measles is one of the more contagious diseases, it spreads quickly once someone is infected."
Two doses of MMR (measles-mumps-rubella) vaccine - given to babies at 12 and then 18 months on the national immunisation schedule - provide lifelong protection against measles in 99 out of 100 vaccinated people.
"Anyone in the age bracket from 1966 to the early '90s who isn't sure whether they've received two doses of measles vaccine should see their GP to get a booster, especially if they're travelling overseas," Mr Gregory said.
Those travelling with small babies could be given an early vaccine, at six months old, under a GP's supervision.
It can take up to 18 days for symptoms to appear following exposure. Symptoms include fever, sore eyes and a cough followed three or four days later by a red, blotchy rash that spreads from the head to the rest of the body.
"It's highly contagious - someone who is sick with measles can leave a room, and someone else can pick up the infection up to half an hour after they go," Mr Gregory said.
"That's why it's important for anyone who believes they have symptoms to call ahead to a doctor's surgery or emergency department so staff can take the necessary precautions.
"It's also important to inform staff if you've recently travelled to countries including New Zealand, or parts of Asia, Africa, and the Middle East."
The virus doesn't respond to anti-virals, so doctors can only treat the symptoms. Up to a third of people with measles have complications and in rare cases it can be fatal.