The patient, who is hospitalized in Orlando, Florida, is the second confirmed MERS case in the United States.
The Florida Department of Health said in a statement that the man is improving but remains hospitalized at the Dr. P. Phillips Hospital.
The patient initially spent 12 hours in the hospital's emergency department before he was moved to an isolation room, raising concerns about whether healthcare workers who had contact with him may have become infected.
MERS causes coughing, fever and sometimes fatal pneumonia, killing an estimated 30 percent of those who are infected.
It is a virus from the same family as SARS, or Severe Acute Respiratory Syndrome, which killed around 800 people worldwide after it first appeared in China in 2002.
Scientists have limited understanding about how the MERS virus spreads, but healthcare workers have proven particularly vulnerable because of their close contact with infected patients.
Both U.S. cases involved healthcare workers who had spent time in hospitals in Saudi Arabia, where MERS infection rates have surged in recent weeks.
Florida health officials said there is no threat of MERS infection for people traveling to the Orlando area.