Sydney health authorities are on high alert after two people were diagnosed with measles after visiting multiple public spaces.
Melbourne is in the grip of an outbreak, with 11 cases recorded in the past fortnight.
Authorities there are concerned infectious people have visited a number of crowded areas including the MCG, central business district and Melbourne Airport.
The Northern Sydney Local Health District on Tuesday issued an alert after a person was diagnosed with measles after returning from the Victorian capital.
The patient spent time in Warringah, Brookvale and Parramatta in late September while infectious.
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A second warning was issued later on Tuesday by the South Eastern Sydney Local Health District after a case of measles in Sutherland Shire.
The second patient had visited the Cronulla Mall on September 25, the Royal Hotel on September 26 and Sutherland Hospital on September 29 and October 1, to name a few locations.
Authorities have warned anyone who visited the listed areas at that time to be aware of symptoms of the serious disease, including a rash, fever, sore eyes and a cough.
There have now been 25 cases of measles across NSW in 2017, including more than a dozen in western Sydney.
