An Illinois resident thought to have been infected by the deadly Middle East respiratory virus after two positive blood tests wasn't, the Centers for Disease Control reports, calling the result a false positive.

The man underwent the tests after spending several hours in contact with an Indiana resident who was later admitted to a hospital where he was confirmed as having a case of MERS infection.

Two blood tests given the Illinois businessman indicated a possible exposure to the MERS virus and a possible response by his immune system, but a follow-up blood test termed "definitive" was negative, CDC officials said.

"It's a little reassuring that this gentleman was not a case," said David Swerdlow of the CDC's National Center for Immunization and Respiratory Diseases.

In a similar incident, a woman from the Mangalore region of southern India, who was quarantined after returning from a trip to Saudi Arabia when she showed respiratory symptoms, was found to test negative for the MERS virus.

She was diagnosed with a minor virus likely tied to age-related ailments, health officials said.

The virus continues to claim victims in the Middle East.

Officials in Saudi Arabia, where the virus was first detected in 2012, said 13 people have died in the last two weeks after being infected with the respiratory virus, bringing the total deaths since the virus' discovery to 186.

One of the coronavirus group of viruses, which includes the common cold and SARS, or severe acute respiratory syndrome, MERS displays symptoms including respiratory distress, pneumonia, fever, and in severe cases kidney failure.

The World Health Organization has reported receiving confirmation of 636 cases of MERS infection globally.

The test on the Illinois man means there have been no confirmed instances of the transmission of the MERS virus within the U.S., the CDC says, although two cases, both in healthcare workers returning home from the Middle East, have been brought into the country.

In addition to the Indiana case, a Florida health worker who lived and worked in Saudi Arabia has been diagnosed with MERS.

The cases in Indiana and Florida are not in any way linked, the CDC said, and both patients are recovering.

In announcing the results of the blood tests on the Illinois man, the CDC said it believed the MERS virus can only be transmitted between humans by sustained or close contact, such as experienced by healthcare workers or between members in a family.

"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 Swedlow 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."