Upon further review: CDC says MERS transmission from first case did not occur, but defends decision to make the call

March 18th, 2015

Though drawing some critical media questions about “jumping the gun” on announcing May 17 what appeared to be the first case of MERS transmission in the United States, the Centers for Disease Control and Prevention stood by its decision even as it confirmed it was a false alarm.

After completing additional and more definitive laboratory tests, the CDC concluded that the Indiana MERS case – the first in the U.S. -- did not spread the coronavirus to an Illinois man during a face-to-face business meeting.

“While we never want to cause undue concern among those who have had contact with a MERS patient, it's our job to move quickly when there's a potential public health threat,” David Swerdlow, MD, the CDC’s incident manager for MERS response, said at a May 27 press conference. “…Understand that the situation is very fluid and our information may change. 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 Illinois resident tested negative for active MERS infection by PCR in the days after the business interaction, but the CDC went the extra step to look for MERS antibodies in the blood that would suggest past infection. Indeed, that appeared to be the case based on the ELISA (enzyme-linked immunosorbent assay) and IFA (immunofluorescence assay) tests. The CDC announced the findings and began follow up on the Illinois man’s contacts, but a more definitive neutralizing antibody assay subsequently revealed the man never acquired MERS.

“Results from these tests are not black and white but require interpretation,” Swerdlow said. “Two of these initial preliminary serology tests, ELISA and IFA, were available late May 16 and indicated the possibility that the Illinois resident had been previously infected with MERS Co-V. This compelled us to notify and test those people with whom he had close contact with in the days following his interaction with the Indiana MERS patient in order to be sure no one else had become ill and to prevent further spread of the virus.”