Health officials have confirmed the first case in the United States of the deadly Middle East respiratory syndrome, a virulent and relatively new condition first reported in Saudi Arabia in 2012.

The unnamed health-care worker is a U.S. citizen who was living in Saudi Arabia, according to an Indiana state health department spokeswoman. He arrived in Chicago about a week ago from Riyadh, the Saudi capital, where he may have picked up the virus while working at a health-care facility, according to the Centers for Disease Control and Prevention.

The man is in insolation and in stable condition at Community Hospital in Munster, Ind., but requires oxygen to help with the symptoms.

Federal, state and local officials are working to minimize the risk of the virus spreading. They are monitoring health-care workers and others who may have had close contact with the patient.

The patient, identified as male by a person familiar with the investigation, was returning to Indiana and flew on April 24 from Riyadh to London and then Chicago. He took a bus from Chicago to Indiana. Three days later, he began to have shortness of breath, coughing and fever. He went to the hospital’s emergency department April 28, according to the Indiana State Department of Health, and was admitted.

Infectious disease experts have been monitoring the virus closely because of the high mortality rate among people with symptoms. The virus has been confirmed in 401 people in 12 countries, and 93 of them died. The cases originated in six countries in the Arabian Peninsula. Most of these people developed severe acute respiratory illness, with fever, cough and shortness of breath.

Saudi Arabia reported 26 infections Tuesday and Wednesday. On April 24, the Saudi health ministry confirmed that 13 people contracted the disease and that there had been two more deaths. Experts said seasonal factors may be at work. The largest reported outbreak to date occurred in April and May 2013 in eastern Saudi Arabia and involved 23 confirmed cases.

Officials do not know the origin of the virus or how it spreads. The MERS virus has been found in camels, but officials don’t know how it is spreading to humans. There is no vaccine or recommended treatment.

“MERS is now in our heartland,” said Anne Schuchat, assistant surgeon general and director of the CDC’s National Center for Immunizations and Respiratory Diseases, during a briefing Friday. But she stressed that the viral disease does not appear to be easily transmittable. “It represents a very low risk to the broader general public.”

She said the patient had been in Saudi Arabia for a “substantial period” before departing April 24. Officials said they don’t have reports of other infected patients in the United States. “It’s a very active investigation,” she said. “This situation is very fluid.”

Because of the patient’s symptoms and travel history, hospital officials decided to test for the virus. The Indiana state public health laboratory and the CDC confirmed the MERS infection in the patient Friday afternoon.

The Munster hospital has contacted all high-risk individuals, state health officials said. In an abundance of caution, the health department said people who visited the emergency department between 6:30 and 9:30 p.m. April 28 should watch for signs and symptoms. It has also established a hotline.

In some countries, the virus has spread from person to person through close contact, such as caring for or living with an infected person. But there is no evidence of sustained spread in community settings, she said.

CDC officials said they have anticipated MERS reaching the United States and have prepared for enhanced laboratory testing and surveillance. They developed guidance for airline flight crews, emergency personnel, and customs and border personnel to report sick travelers to the CDC.

CDC and Indiana health officials are not sure how the patient became infected. Schuchat said she did not know whether the patient had been involved in treating MERS cases in Saudi Arabia. Officials also do not know how many people have had close contact with the patient.

“In this interconnected world we live in, we expected MERS-CoV to make its way to the United States,” said Tom Frieden, director of the CDC. “We have been preparing since 2012 for this possibility.”

The virus comes from the same family as the severe acute respiratory syndrome, or SARS, coronavirus, which killed almost 800 people worldwide in 2003.

The incubation period of the virus — the time between exposure and development of symptoms — is about five days, similar to SARS.

While experts do not know how this virus is spread, the CDC advises Americans to help protect themselves by washing hands often, avoiding close contact with people who are sick, avoiding touches to their eyes, nose and/or mouth with unwashed hands, and disinfecting frequently touched surfaces.

People who develop fever and cough or shortness of breath within 14 days after traveling from countries in or near the Arabian Peninsula should see a doctor.