People in western Sydney and on Queensland's Sunshine Coast are being urged to watch for measles symptoms after three cases of the highly infectious respiratory illness were diagnosed.
NSW Health says a baby spent time at Parramatta and Westmead on Monday while infectious.
The baby, who is too young to be vaccinated against measles, acquired the infection while in India before returning to Sydney.
On Thursday the Sunshine Coast Hospital and Health Service Public Health Unit issued a public health alert over two cases of measles in a family who returned from overseas on March 13.
Coles Nambour has been identified as a venue of concern, with the family visiting on Monday afternoon.
Staff and community members who visited the venue on that day are urged to monitor their health and that of their families, the hospital said in a statement on Wednesday evening.
"This is a reminder that everyone should take the opportunity to make sure they are vaccinated against measles," said the hospital, which is managing the two cases.
NSW Health's Christine Selvey is urging people who may be susceptible to measles, and anyone born in or after 1966 who has not received two doses, to get vaccinated by Thursday.
"Measles is a highly contagious infection and the most vulnerable are infants under 12 months, who are too young to be vaccinated against it,' Dr Selvey said on Wednesday.
People who are not fully vaccinated and those with a weakened immune system are also vulnerable with the infection easily spread through coughing or sneezing.
Symptoms include fever, sore eyes, runny nose and a cough followed three or four days later by a red, blotchy rash spreading from the head and neck to the rest of the body.
It can take up to 18 days for symptoms to appear after exposure and anyone who develops signs should call their GP to ensure they don't spend time in the waiting room with other patients, Dr Selvey said.
The measles-mumps-rubella vaccine is free for anyone born during or after 1966 who hasn't already had two doses.
Anyone who was at three western Sydney locations below on Monday should be alert for measles symptoms until April 14.
* The Children's Hospital at Westmead emergency department waiting room between 12pm and 9:30pm
* Argyle Street Medical Centre at Parramatta between 9:15am and 10:00am
* Westfield Parramatta between 9am and 10am
