NSW Health has put the city's citizens and visitors on the alert for symptoms - which they may already be experiencing - after the newest case, who was infectious in the community several weeks ago, was discovered.

Symptoms of measles - which may include fever, runny nose, sore eyes and cough, usually followed several days later by a red, blotchy rash that spreads from the head to the rest of the body - can take almost three weeks to emerge after exposure.

The Wagga case, which the Murrumbidgee Local Health District said is linked to the initial one that prompted a health warning on February 25, spent extended periods at a Wagga CBD retail business as well as other venues over four days from the end of last month.

"The new case was infectious in the community more than two weeks ago, so there may already be spread of measles that has not yet been detected," the MLHD said.

People who were at Blowes Clothing on Baylis Street between 9am and 6pm on Tuesday, February 27 through Friday, March 1, and again between 9am and 2.30pm on Saturday, March 2, may have been exposed to the virus.

Other sites for potential exposure include the Sturt Mall, including the food court, between 1pm and 2pm on February 27.

Anyone who was in Forsyth Street eatery Tasty Tibetan Treats between 1pm and 2pm on February 28, and between 12.45pm and 2pm on March 1, is also urged to be vigilant for symptoms.

Those who develop symptoms should call ahead when seeking medical help to avoid spreading the virus, MLHD public health physician Anton Forsyth said.

"it's important for people to stay vigilant, and if they develop symptoms, to please call ahead to their GP or emergency department to ensure they do not spend time in the waiting room with other patients," Dr Forsyth said.

"NSW Health is also urging everyone to ensure they are up to date with their measles vaccinations.

"If you were born in 1966 or after, you need to receive two doses of measles vaccine to be fully vaccinated.

"If you are unsure whether you have received two doses, it is best to get a vaccine, as additional doses are safe."

The initial case detected in February had recently returned from South Asia, where there have been ongoing outbreaks of the virus, and transited through Melbourne Airport before arriving in Wagga.

The measles-mumps-rubella (MMR) vaccine is free for anyone in NSW born during or after 1966 who hasn't already had two doses, and is part of the national immunisation program for children at 12 and 18 months.

The MLHD advises the public that if they or a loved one are experiencing measles symptoms, or have questions about measles, to call their GP or Healthdirect on 1800 022 222.

For more information on measles, you can view the NSW Health measles factsheet.