Health authorities fear it could be spreading undetected in the community.

Measles cases surge across Australia

Australians have been warned to be on high alert as cases of “the most infectious virus” surge around the world.

Health authorities say measles, which was effectively eliminated here in 2014, may already be spreading undetected in the community, fuelled by overseas outbreaks and falling vaccination rates.

There has been 105 cases recorded in Australia this year, mainly linked to travellers from South East Asia.

New South Wales has experienced the biggest spike, while alerts have also been issued in Victoria, Queensland and Western Australia.

“We’ve seen in New South Wales 46 cases already this year, and that’s more than we’ve seen in New South Wales for the past 10 years,” public health physician David Durrheim told 7NEWS.

Health authorities are especially concerned about a handful of infections that cannot be linked.

Globally, outbreaks have been reported in Europe, America and Asia.

The worst is currently occurring in Bangladesh where more than 300 people, mostly children, have died.

“This is something that is preventable. These deaths should not occur,” paediatric infectious diseases physician Linny Phuong told 7NEWS.

Symptoms start about 10 days after exposure and include fever, tiredness, a cough and runny nose.

A few days later the telltale skin rash starts on the face and spreads to the body.

“By the time they’re diagnosed they have often been in contact with so many people,” Phuong said.

With vaccination rates falling, doctors fear the number of cases will only get worse.

“There is so much misinformation and disinformation out there that parents are now questioning the science,” Phuong said.

The advice for Australians travelling overseas is to ensure they are vaccinated before leaving.