Health authorities have issued a Territory-wide measles alert after an infected woman visited Darwin for five days last week.
The overseas visitor spent time at crowded locations in Darwin including the Museum and Art Gallery of the NT, Darwin airport and the Mindil Beach Markets.
She was infectious between October 12-17 while in the Top End, also visiting Kakadu during that period.
Acting Director of the Centre for Disease Control, Dr Peter Markey, said Queensland health authorities advised their Territory counterparts that the woman was later hospitalised with measles in Cairns.
The extremely infectious disease is serious and up to one third of cases will experience a complication such as pneumonia, or encephalitis.
Dr Markey said anyone who is not immune to measles and who visited those areas at that time should be alert to the symptoms.
"If they develop a fever and a cough, with or without a rash, over the next two weeks they should avoid public places and seek immediate medical advice," he said.
"But anybody considering visiting a clinic with measles-like symptoms should phone in advance so arrangements can be made to prevent the spread of the virus to others."
People who are not immune can easily catch it in public places, Dr Markey said.
It is spread by coughing and sneezing.
The early symptoms of measles are fever, cough, runny nose and sore eyes, with a red blotchy rash following two to four days later.
