A healthcare worker being treated in Indiana with the first US case of the often fatal Middle East Respiratory Syndrome (Mers) is in good condition and improving daily, the state health department said on Sunday.

State and federal health officials confirmed on Friday that the man had been diagnosed with the virus after traveling to Riyadh, Saudi Arabia, and exhibiting symptoms upon his return to the US.

"We are very pleased the patient is improving and no other cases have been identified at this time," said Dr William VanNess II, Indiana's state health commissioner.

Medical staff members who came into direct contact with the ill man before he was placed in full isolation at Community Hospital in Munster, where he remains, were taken off duty and put in temporary home isolation, state health officials said.

They will be allowed back to work after the incubation period ends and their laboratory results are confirmed to be negative for the virus, the state said. Mers symptoms can take up to 14 days to occur, and the virus has no known treatments.

The first confirmed case of Mers in the US raised fresh concerns about the rapid spread of the disease, which proves fatal in about a third of infections. - Reuters