South Australia has recorded its first case of measles in a resident since 2019 after a three-year-old boy was infected.

The boy, from regional South Australia, was infected while travelling overseas.

SA Health warned anyone who wasn't fully vaccinated against the measles to keep watch for symptoms over the next few weeks, particularly if they visited certain areas during specific times.

The warning areas included Murray Bridge Swimming Centre on Friday, March 17 between 4pm and 6pm, and the Murray Bridge hospital emergency department waiting area on Wednesday, March 22 between 9.30am and 1pm.

The boy also visited the waiting area on Thursday, March 23 between 9am and 9.45am.

There were two additional warning areas for Thursday: the Bridge Clinic at Murray Bridge between 9.30am and 11.15am, and the Women's and Children's Hospital emergency department waiting area between noon and 12.45pm.

Symptoms start with fever, cough, runny nose and sore eyes, which were followed by a blotchy rash, SA Health said.

The rash usually began on the head and then spread down the body.

It was vital people made sure they had two doses of the measles vaccine to protect themselves, SA Health Disease Prevention and Control branch director Louise Flood said.

Those travelling overseas should check their vaccination records and request the vaccine well in advance if not fully vaccinated and born after or during 1966, she said.

People born in the late 1960s to mid-1980s might believe they were fully vaccinated but could have only received one dose of the measles vaccine.

Australian authorities have fielded four measles notifications so far this year, with Tasmania also recording its first case since 2019 last month.

The person was aged in their late 20s and had also recently returned from overseas to Tasmania when they tested positive for measles.

More measles case are expected in Australia as more people travel overseas, SA Health said.