Hundreds of West Australians could have been exposed to the measles virus after a Perth man contracted the disease while holidaying overseas.

The man came down with measles in Bali in late November.

The Health Department advises that measles is contagious for up to five days before a rash develops and four days following that.

Communicable Disease Control director Dr Paul Armstrong said it was extremely contagious.

“Even if people don’t have direct contact with somebody and they’re in a room with someone with measles and they don’t have immunity to measles, then they are likely to get it,” he said.

Most people in Australia are immune to measles due to vaccination.

“There are a group of people born after 1966 who haven’t had two doses of measles-containing vaccine,” Dr Armstrong said.

“They’re the ones who aren’t immune to measles and the ones we’re particularly concerned about.”

During the time the man was contagious he travelled through Perth’s southern suburbs where he may have come into contact with hundreds of people.

Possible contact during contagious phase

The department has issued a list of dates and places the man was during the contagion phase:

Dr Armstrong said it was important to be aware of the symptoms of measles and how to react.

A national ad campaign against measles.

“The symptoms of measles include first of all a sore throat and a cough, sore eyes, a runny nose and fever,” he said.

“After a number of days they develop a rash which usually starts on the upper part of the body and extends more widely.”

He said anyone developing symptoms should not turn up to an emergency department or doctor’s surgery and risk infecting others.

“They should ring ahead and make sure they don’t infect other people and special precautions can be put in place when they do turn up to the medical facility,” Dr Armstrong said.

He said the people who had been exposed could develop symptoms for the next week to 10 days.

Locally acquired measles has been stamped out in WA but Dr Armstrong said there had been a three-fold increase in cases coming back from overseas this year.

Western Australia records an average of 12 cases per year, but this year 38 cases were diagnosed, possibly to do with an outbreak in the Philippines earlier this year.

It puts pressure on the Health Department, which must attempt to contact all of the people that came into contact with the carrier.

Dr Armstrong said it was a timely reminder for travellers to make sure they were vaccinated for measles.

This post was originally appeared on ABC News and is republished here with full permission.