By Karen Kaplan, Los Angeles Times

Health officials at the Center for Disease Control and Prevention said Wednesday an Illinois man did not contract MERS from an infected business associate after all.

The case, announced May 17, was believed to have been the first instance of human-to-human transmission of the Middle East Respiratory Syndrome coronavirus on U.S. soil. But upon further analysis, it wasn’t, said Dr. David Swerdlow, the epidemiologist who is leading the CDC’s response to MERS.

Initial blood tests “indicated the possibility that the unidentified Illinois resident had been previously infected with MERS-CoV,” Swerdlow said in a statement. But now that the results of a more definitive test are in, the CDC has concluded the man was never infected.

Public health officials investigated the Illinois man after a health care worker from Saudi Arabia was diagnosed with MERS in Munster, Indiana. The Indiana patient was the first person with a confirmed case of MERS in the U.S.

The Illinois man aroused suspicion because he had two business meetings with the Indiana patient in the days before he was hospitalized. The two men shook hands and sat face-to-face for more than half an hour during their first meeting, Swerdlow told reporters May 17. The second meeting was shorter.

The Illinois man never felt sick and never sought medical care. But public health officials decided his contact with the Indiana patient was close enough to warrant testing for MERS antibodies, which are made by the immune system to fight off an infection.

Officials performed three types of blood tests. Two of them — an enzyme-linked immunosorbant assay (ELISA) and an immunofluorescent assay (IFA) — seemed to indicate the presence of MERS antibodies. Those preliminary results prompted Swerdlow to announce the Illinois case May 17, which appeared to be the first homegrown case of MERS in the United States.

In the days since then, officials completed a more time-consuming blood test called a neutralizing antibody assay. With all of the results in and carefully interpreted, CDC officials now say the Illinois man was never infected with MERS.

“It is our job to move quickly when there is a potential public health threat,” Swerdlow said Wednesday. “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 Indiana patient has been released from the hospital and is doing well. A second patient in Florida has also fully recovered and was discharged from the hospital this month. That man is also a health care worker who had recently traveled to Saudi Arabia. The two cases are not linked, according to the CDC.

MERS is a respiratory disease that is thought to have originated in camels before spreading to people. It was first detected in Saudi Arabia in 2012. Humans have no natural defense against the virus, which has killed about 30 percent of the people known to be infected with it.

As of Wednesday, the World Health Organization has announced 635 laboratory-confirmed cases of MERS. Among those patients, 193 have died.

So far, there is no evidence that MERS spreads easily from person to person. There have been some cases of transmission between close contacts, such as patients and the health care providers who care for them.

Photo: Striatic via Flickr