Microscopic view of MERS coronavirus (U.S. National Institutes of Health)
ATLANTA, May 28 (UPI) -- Officials at the Centers for Disease Control said Wednesday more definitive laboratory tests show an Indiana MERS patient did not spread the virus to an Illinois man during a business meeting.
On May 17, the CDC reported that the first confirmed case of Middle East Respiratory Syndrome -- a U.S. citizen who works as a healthcare provider in Saudi Arabia and traveled by plane to Munster, Ind., and is referred to as the "Indiana patient" -- had a lengthy business meeting with an Illinois man. Neither man's identity has been made public.
The CDC, state and local health officials conducted voluntary testing of people who had contact with the Indiana patient. The Indiana patient, who had been hospitalized with MERS in Community Hospital in Munster, Ind., has recovered and been sent to home isolation.
One type of test -- polymerase chain reaction -- uses respiratory samples and can quickly indicate if a person has an active infection with the MERS coronavirus. Serology tests use samples of blood and are designed to look for antibodies to MERS-CoV.
Antibodies indicate a person was infected with the virus at one time and developed an immune response. CDC officials said they did three separate serology tests -- ELISA or enzyme-linked immunosorbent assay, IFA or immunofluorescent assay and a third more definitive test, the neutralizing antibody assay.
The Illinois man, who had extended face-to-face contact with the Indiana patient, tested negative for active MERS-CoV infection via the PCR test. However, preliminary ELISA and IFA test results announced by CDC on May 17 indicated the Illinois resident was positive for MERS-CoV antibodies.
"The initial ELISA and IFA serology results indicated the possibility that the Illinois resident had been previously infected with MERS-CoV," Dr. David Swerdlow, associate director for science at the CDC's National Center for Immunization and Respiratory Diseases and head of the CDC's MERS response, told reporters in a telephone news conference.
"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."
Since then, the CDC did the slower, definitive serology test -- the neutralizing antibody test -- which needs at least five days. The CDC concluded "the Illinois resident was not previously infected with MERS-CoV."
"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," Swerdlow said.
"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."
Since the Indiana patient was confirmed with MERS, to date, none of the people he had prolonged contact with was found to have an active MERS-CoV infection. A second unrelated MERS patient was confirmed in Florida -- also a U.S. citizen who works in healthcare in Saudi Arabia who traveled back to the United States.
Investigations are still ongoing, but "there is currently no evidence of sustained spread of MERS-CoV in community settings, the CDC said.