There are three cases of coronavirus in NSW and four other people are being tested for the disease, NSW health officials said on Saturday night.

The three men aged 53, 43 and 35 had recently travelled from China, and are now in isolation in a Sydney hospital.

"I'd like to thank each of these three people because they have been exemplary in the way that they presented themselves, to have a medical test, and to have the necessary pathology in due course, when it was appropriate from the medical practitioners point of view," the NSW Minister for Health, Brad Hazzard said.

The first man, 35, arrived in Australia on January 6, but did not develop symptoms until January 15.