ACT public health physician Dr Kerryn Coleman said the resident acquired the infection on a recent overseas trip. It is not linked to the previous two cases.

The person attended Canberra Airport between 10am and 11am on Sunday while infectious.

“Anyone who was at the Canberra Airport on that Sunday should be aware for signs and symptoms of measles from now until 24 February 2019," Dr Coleman said.

“We urge anyone with symptoms of measles to seek medical advice and to advise their health care provider before arriving at the clinic so that appropriate infection control precautions can be put in place to stop the spread of infection.

“Measles continues to circulate in many overseas countries, so we urge people travelling overseas should check their immune status before they leave.

“Measles can be highly contagious among people who are not fully immunised.

"This is a timely reminder for Canberrans to ensure their vaccinations are up to date."

Two other cases of measles - which were linked - were reported in December and January, with the December case also believed to ave been acquired overseas.

“People born in 1966 and later who do not have two recorded doses of MMR vaccine are also considered susceptible to measles," Dr Coleman said.

The symptoms of measles may include fever, tiredness, runny nose, sore eyes and a cough, followed by a rash, which appears two to seven days later.

People generally develop symptoms seven to 18 days after being exposed to a person with infectious measles, with 10 days being more common.

People are infectious from five days before they develop a rash until four days after.