Macarthur residents are being urged to look out for measles symptoms after a man affected with the diseases visited the area.
The South Western Sydney Local Health District issues the urgent warning this afternoon.
The man, who arrived with the disease from overseas, brings the total number of cases in the Health District (which stretches from Bankstown to Bowral) to three since the start of 2020.
There have been 11 cases in the state in that time.
The man visited Mount Annan Marketplace, including the Ultra Care Medical Centre and pharmacy, between 1pm and 3pm on Monday, January 20. He was infectious at the time.
The Health District's Public Health Unit director Dr Naru Pal said the locations did not pose any ongoing risk to the public.
However, anyone who was in the same place at the same time as the man should look out for symptoms until February 7 as they take up to 18 days to develop.
"Out Public Health Unit is working with the Ultra Care Medical Centre to directly contact patients who may have been in contact with the man to offer information and preventive treatment, if required," Dr Pal said.
"Symptoms to watch out for include fever, sore eyes, runny nose and a cough followed three or four days later by a blotchy rash that spreads from the head to the rest of the body."
Measles is highly contagious and is spread in the air through coughing or sneezing by someone who is unwell with the disease.
"People with measles symptoms should stay home from work or school to avoid exposing others to the disease, particularly vulnerable people, such as infants and those who are pregnant or immunocompromised," Dr Pal said.
"Anyone seeking medical attention for possible symptoms should call their doctor before attending so that arrangements can be made to minimise the risk of the infection spreading."
NSW Health provides the safe and highly effective measles-mumps-rubella vaccine for free to anyone born during or after 1966 who hasn't had two doses.
If you are unsure whether you have had two doses, it is quite safe to have another.
"It's important to be fully vaccinated, not only to protect yourself, but also to protect vulnerable people that you may unknowingly spread the virus to, such as babies," Dr Pal said.
For young children, the measles vaccine is recommended at 12 months and again at 18 months of age.
For more information on measles, visit: www.health.nsw.gov.au/Infectious/factsheets/Pages/Measles_Factsheet.aspx.
If you are concerned you may be at risk of measles, contact SWS LHD public health unit on 1300 066 055