A fifth case of measles has been reported in NSW, with the infected man having visited bars, a shopping centre and a gym in inner Sydney.

The unvaccinated man, aged in his 20s, developed measles this week nine days after his first exposure to the disease, carried by a child visiting from Thailand.

Darling Harbour bar Bungalow 8, Albion Place Hotel, Anytime Fitness Newtown and Marrickville Metro Shopping Centre are among the places he visited while infectious between January 4 and 9.

NSW Health warned people who were in the same locations at the same time to remain alert for symptoms until January 26.

Measles can take up to 18 days after exposure to show symptoms.

The man's itinerary included:

* Bungalow 8 from 7pm Friday to 3am Saturday

* a train from Newtown to Town Hall, time at Albion Place Hotel and a bus to King St Newtown between 7pm and 11.30pm on Saturday

* Anytime Fitness Newtown on Monday (5-7pm) and Tuesday (5-6pm)

* Marrickville Metro from 1.30 to 2.30pm on Wednesday

* Service NSW Marrickville from 1.45pm and 2pm on Wednesday

Five people in NSW have been diagnosed with the highly contagious disease since Christmas.

The state recorded just 17 cases between January and mid-December.

"If you develop symptoms, please call ahead to your GP so that you do not wait in the waiting room with other patients," NSW Health Communicable Diseases director Vicky Sheppeard said in a statement.

Dr Sheppeard reminded the community the measles-mumps-rubella (MMR) vaccine is free for those aged one to 52

"If you are unsure whether you have had two doses, it is quite safe to have another dose," she said.