The New York State Department of Health has issued an alert after an Australian tourist carrying measles visited a number of hotels and the Metropolitan Museum of Art, warning people they may have been exposed to the highly contagious disease.

The virus remains alive in the air and on surfaces for up to two hours after the carrier leaves the area, and is spread by direct contact with nasal or throat secretions by infected people.

The Centres for Disease Control and Prevention said it was notoriously contagious for people who have not been immunised, with a 90 per cent infection rate for those near a carrier.

The health department said the Australian had travelled around New York City from February 16 to February 21, and said anyone who visited the La Quinta Inn, the Metropolitan Museum of Art, Watchtower Educational Center, the Best Western Hotel, Comfort Inn & Suites Goshen, Excel Urgent Care and Orange Regional Medical Center during those dates may have been exposed.

It warned anyone who had not been immunised should contact their health provider if they developed symptoms, which include a fever, rash, cough, conjunctivitis or a runny nose. Symptoms usually appear 10 to 12 days after exposure.

Just over 90 per cent of children in the US receive measles vaccinations, which is over 90 per cent effective.

Recent spikes in measles cases have been attributed to more cases in countries to which Americans often travel, and in pockets of US communities with unvaccinated people.

Although the risk of developing the virus is low for those who have been immunised, the episode is noteworthy given New York City's population density and the Australian's travel route.

Around 8.5 million people called the city their home as of 2016, and the Metropolitan Museum of Art alone notched up 7 million visits in fiscal 2017, it said in its annual review.