(Adds comments from CDC, details of tests)
NEW YORK May 28 U.S. health officials on Wednesday walked back their earlier conclusion that a healthcare worker who traveled from Saudi Arabia to Indiana and was diagnosed with Middle East Respiratory Virus (MERS) had infected an acquaintance upon his return.
The U.S. Centers for Disease Control and Prevention said in a statement that additional and more definitive laboratory tests showed that the healthcare worker did not spread the deadly virus to an Illinois business associate he met with twice before becoming ill and seeking treatment at a hospital.
The case in Illinois had been considered the first direct transmission of the MERS virus on U.S. soil. It raised alarms that it might be transmissible outside hospitals and other healthcare settings, especially by doctors, nurses and others who had worked in Saudi Arabia, the epicenter of MERS.
CDC and state and local public health officials are conducting voluntary tests on people who had contact with the Indiana patient and the second U.S. MERS patient, a man in Florida, who had also returned from Saudi Arabia.
Earlier this month the Illinois man tested negative for MERS in a method that uses respiratory samples and can quickly indicate if a person has an active viral infection. But he tested positive on two blood tests that are considered more definitive.
Those initial blood-test results "indicated the possibility" the Illinois resident was infected with MERS, Dr David Swerdlow, who is leading CDC's MERS response, said in a statement.
"This compelled us to notify and test those people with whom he had close contact in the days following his interaction with the Indiana MERS patient."
The blood tests included one that takes several days to yield a result, which was that the Illinois resident was not infected with MERS.
"While we never want to cause undue concern among those who have had contact with a MERS patient, it is our job to move quickly when there is a potential public health threat," said Swerdlow. "Because there is still much we don't know about this virus, we will continue to err on the side of caution when responding to and investigating cases of MERS in this country."
The new analysis means that no MERS infections have been found in any of the contacts of the two MERS patients in the U.S.
Since it was first identified in 2012, MERS has infected at least 536 people, according to the World Health Organization, and killed 145. It causes fever, body aches, cough and sometimes deadly pneumonia.
How MERS is transmitted from person to person is not well understood, but most cases have occurred through close physical contact with an infected person or animal, such as a camel, which is thought to be a reservoir for the virus. (Reporting by Sharon Begley; Editing by Chizu Nomiyama)