A baby who recently returned from overseas has triggered a health alert after visiting a cafe while infected with measles.

NSW Health raised the alarm after the nine-month-old infant was taken to locations in Sydney's inner west and southwest.

The child had recently returned from Asia, where there has been an outbreak of measles in countries including Pakistan and India.

People might have been exposed to the infectious disease when the infant visited Five Star Coffee and Nuts on Yerrick Road in Lakemba between 3pm and 5pm on Friday, the health authority said.

Leena Gupta, from Sydney Local Health District, said the location posed no ongoing risk but she advised anyone who visited the shop at the time to be alert for symptoms.

"Symptoms to watch out for include fever, sore eyes and a cough, usually followed three or four days later by a red, blotchy rash that spreads from the head to the rest of the body," she said.

Measles is a highly contagious but vaccine-preventable disease that is spread through the air via coughs or sneezes.

The viral illness can lead to serious complications, including pneumonia and encephalitis.

It can take up to 18 days for symptoms to appear after exposure.

"It's important for people to stay vigilant if they've been exposed and if they develop symptoms, to please call ahead to your GP or emergency department to ensure you do not spend time in the waiting room with other patients," Dr Gupta said.

Anyone born during or after 1966 must have two doses of the measles vaccine, which is free in NSW.

Dr Gupta said the vaccination was particularly important before overseas travel because measles outbreaks were occurring in several regions internationally.

The measles-mumps-rubella vaccine is included on the National Immunisation Program for children at 12 and 18 months of age.

People who are unsure about whether they have had two doses should get a vaccine, with extra doses available from GPs and pharmacies, NSW Health said.