Health authorities have issued a measles alert for Perth, including the popular school holiday venue Perth Zoo and shopping giant Ikea.

The WA Health Department said people were being urged to be on the look-out for symptoms of the viral infection, following a confirmed cases of measles in a person who visited the two public sites last week.

Children and adults who had been inadvertently exposed were at risk of developing measles if they were not already immune.

The department said people should be vigilant for the onset of measles symptoms until January 20 if they visited Perth Zoo on New Year’s Day or IKEA’s Innaloo store at lunchtime on January 2.

The patient had no recent history of travel overseas and is believed to have acquired their measles infection in WA’s South West.

The department said parents, especially those in the South West, were urged to make sure their children received their measles vaccinations on schedule. Measles vaccine is currently given to children at 12 and 18 months of age.

Director of Communicable Diseases Paul Armstrong said public health staff had provided information to people who were exposed to the recent case where they were known, but it was not possible to identify and specifically warn people who were in public places.

“Measles is a serious and highly contagious viral illness spread by tiny droplets released when infected people cough and sneeze,” Dr Armstrong said.

“Every measles case is treated as a public health emergency because of the risk of local spread, including to those most vulnerable to infection, such as infants too young to be vaccinated, those with compromised immune systems and pregnant women who are not already immune through vaccination or previous infection.”

People with measles typically developed symptoms approximately 10 days after being exposed to the virus, but this could vary from 7 to 18 days.

Early symptoms include fever, cough, runny nose and sore eyes, followed by a red blotchy rash three or four days later. The rash usually started on the face and spread to the rest of the body.

“Anyone who has had a potential exposure to measles, and who develops a fever with these other symptoms should see a doctor,” Dr Armstrong said.

“It is important to call ahead of travelling to a clinic or emergency department so that they can be isolated from infecting other patients and staff when they arrive.”

Complications from measles include ear infections and pneumonia, and about 30 per cent of cases require a hospital admission, while one person in every 1000 will develop encephalitis, or inflammation of the brain.