Measles is a highly infectious airborne disease that spreads when an infected person breathes, coughs or sneezes.
Nine in 10 unvaccinated people exposed to the virus can contract the illness.
Infectious diseases specialist Dr Sanjaya Senanayake is an Associate Professor of Medicine at the Australian National University.
"If someone goes into a hospital waiting room, with measles and waits there for about 15 minutes and then leaves, for the next two hours, anyone going into that room will be exposed to measles. So really, really infectious."
Symptoms - which occur between 10 and 18 days after exposure - include a rash a runny nose, cough, sore eyes and a fever.
Most people recover, but measles can lead to health complications - including ear infections, pneumonia, and encephalitis, which is the swelling of the brain.
In some cases, it can result in death.
Dr Senanayake says measles is rare in Australia - thanks to vaccinations - but a global surge in cases has health authorities on alert.
"We've done really well with immunisations in Australia with regard to lots of infections, particularly measles. In fact, in 2014 the World Health Organization regarded measles as eliminated within Australia. However, this does not mean we don't see measles in Australia because measles is still active in other parts of the world. So people coming into Australia - either Australians returning from overseas or tourists visiting Australia - can bring measles back here. And we can see small outbreaks occurring - as we have been seeing in different parts of the country this year."
Twenty-eight cases of measles have been detected in Australia so far this year. That's more than total number of cases reported for the entirety of 2023 - 26 cases.
Around 50 countries are experiencing what the World Health Organization describes as "large and disruptive" measles outbreaks.
This is mainly due to a decline in vaccination coverage during the pandemic, when an estimated 60 million children missed their measles immunisations.
Catch-up efforts are now critical, with cases soaring in Europe.
More cases have also been recorded in the US, India and Indonesia.
The World Health Organisation is also warning of a measles resurgence in the Western Pacific, where 3.6 million children missed their routine immunisations between 2020 and 2022.
Last year, cases more than tripled in the region, which includes Australia, Pacific Island Nations, China, the Philippines and Malaysia. The last two countries are driving up case numbers.
Dr Saia Ma’u Piukala [[Sigh-yah Mah Piu-kalah]] is the World Health Organization Regional Director for the Western Pacific.
"During the COVID-19 pandemic there was an immunity gap with the lockdown and people not travelling. So parents can take their children for immunisation. And the healthcare workforce has been concentrating on COVID-19 vaccination and COVID cases. But most of the times, it is imported cases where they have measles outbreak. There are two countries in the Western Pacific region that reported the highest rates of measles in 2023. They were Malaysia and the Philippines."]]
Dr Senanayake says a large measles outbreak in Australia is unlikely, but he's stressing the need for people to check if they’re protected - particularly if you're heading overseas.
"It's really important that we don't get complacent about our own vaccination rates. If you're planning a trip and you've got time to look into these things, you can always meet your doctor and double check your measles vaccination status. And that can be done just by looking at immunisation records or even doing a blood test to look at antibody levels."
Measles immunisations are recommended for babies at 12 months.
Infants as young as six months of age can receive the measles-mumps-rubella vaccine prior to travel overseas to countries where measles outbreaks are occurring.
Two doses are about 97 per cent effective and protection is lifelong.
