While these are the known locations the three cases visited while infectious, the area of risk could potentially be far broader, said Vicky Sheppeard, Director Communicable Diseases at NSW Health. Sydneysiders who have not been vaccinated should be on high alert, health authorities say. Credit:AP Dr Sheppeard warned people in Sydney who had not had their two doses of the measles vaccine should be on high alert in the coming days and weeks. "The measles virus is highly contagious and is spread through the air through coughing or sneezing by someone who is unwell with the disease," Dr Sheppeard said. "A highly effective measles vaccine has been freely available for many years and it is vital for everyone, including adults and children, to have two doses of the measles vaccine during their lifetime."

Symptoms of measles include fever, sore eyes 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's an average year as far as the flu season goes, Vicky Sheppeard says. Credit:Edwina Pickles Measles can have serious complications, particularly for young children. "Children or adults born during or since 1966 who do not have documented evidence of receiving two doses of measles vaccine, or evidence of previous measles infection, are likely to be susceptible to measles and should be vaccinated as soon as possible," Dr Sheppeard said. A case of measles. Credit:US Centres for Disease Control and Prevention

"If you develop the symptoms of measles, seek medical advice. Please call ahead to your doctor or emergency department so that arrangements can be made to keep you away from others to minimise the risk of infection." Anyone born during or since 1966 should have two doses of vaccine (at least four weeks apart). For young children, the measles vaccine is recommended at 12 months and again at 18 months of age. NSW Health offers free MMR (measles-mumps-rubella) vaccine through GPs for people born during or since 1966 with no records of having received two doses of MMR vaccine. Dr Sheppeard said the first adult measles case reported this month had acquired the infection outside of Australia. "It's important that people planning to travel overseas are fully vaccinated against measles before departure to reduce their risk of contracting measles and then bringing the disease back to Australia and putting others at risk.

"NSW Health is urging people to watch for symptoms of measles after another two adults contracted the highly contagious disease in Sydney following a case reported earlier this month