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.