(CNN) -- An Illinois businessman believed to have had Middle East Respiratory Syndrome, or MERS, was not infected with the virus, Centers for Disease Control and Prevention officials said Wednesday.
The finding means there has been no confirmed transmission of the virus within the United States. Two confirmed cases of MERS have been imported into the country.
He had met with the first confirmed MERS patient in the United States, an American resident who had traveled from Saudi Arabia to Indiana. The face-to-face meeting included a handshake with the infected patient.
Public health officials said they became concerned about the potential for a more contagious virus when preliminary testing indicated MERS may have been transmitted during that meeting.
However, after more extensive blood tests, the "CDC has concluded that the Illinois resident was not previously infected with MERS-CoV," according to the agency.
As of Wednesday, the World Health Organization has received reports of 636 laboratory-confirmed cases of infection with MERS.
The first instance of MERS in the United States occurred in the patient who was working as a health care provider in Saudi Arabia and then traveled to Indiana. In the second case, a health care provider who lives and works in Saudi Arabia received a MERS diagnosis in Florida.
The Florida and Indiana cases are not linked, said Dr. Anne Schuchat, director of the CDC's National Center for Immunization and Respiratory Diseases.
MERS is a coronavirus, the same group of viruses as the common cold. It attacks the respiratory system, according to the CDC. Symptoms can lead to pneumonia or kidney failure. It was first found in the Arabian Peninsula in 2012.
Experts believe the MERS coronavirus requires close and sustained contact, such as between family members or health care workers, to spread between humans.
"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," the CDC's Dr. David Swerdlow said in a statement. "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."
CNN's Miriam Falco contributed to this report.