A health care worker who had travelled to Saudi Arabia was confirmed as the first US case of Middle East respiratory virus (Mers), an often fatal illness.
The male patient took a British Airways flight on April 24 from Riyadh to London, where he changed flights at Heathrow airport to fly to the United States. He landed in Chicago and took a bus to an undisclosed city in the Midwestern state of Indiana.
On April 27, he experienced respiratory symptoms, including fever, cough and shortness of breath. The man visited Community Hospital in Munster, Indiana, on April 28 and was admitted that day.
Because of his travel history, health officials tested him for Mers, and sent the samples to the US Centres for Disease Control and Prevention (CDC), which confirmed the presence of the virus on Friday.
The virus is similar to the one that caused Sars, which emerged in China in late 2002 and killed some 800 people.
Mers was first detected in Saudi Arabia in 2012.
Dr Anne Schuchat, director of the CDC's National Centre for Immunisation and Respiratory Diseases, said the case was "of great concern because of [Mers'] virulence", proving fatal in about a third of infections.
Schuchat said the patient was now in stable condition and there were no other suspected cases of Mers in the US. In Britain, public health officials said they were contacting any passengers who had been sitting near the patient.
Although the vast majority of Mers cases have been in Saudi Arabia and the Middle East, the discovery of sporadic cases in Britain, Greece, France, Italy, Malaysia and elsewhere have raised concerns about the potential global spread of the disease by infected airline passengers.
With the addition of the US patient, 262 people in 12 countries have been confirmed to have Mers infections and have been reported to the World Health Organisation. Of those, 93 have died, Schuchat said.
Dr Wayne Marasco, an infectious disease specialist at Dana-Farber Cancer Institute in Boston, suggested thermal scanners such as those China deployed during the 2003 Sars epidemic would not help much to identify infected travellers at airports because the incubation period for Mers is two to 14 days, "so an asymptomatic traveller could make it through a thermal scanner".