The third case of Middle East Respiratory Syndrome (MERS) identified on American soil has been confirmed in Illinois. The U.S. Centers for Disease Control and Prevention (CDC) postulated that the individual most likely contracted the virus when he came in contact with the patient registered as the first case of MERS in the US, through no further contact than a handshake for a business transaction.

The first case of MERS was found in an Indiana healthcare worker, who had returned from Saudi Arabia on April 24 this year, and fell ill shortly after. The patient was successfully treated in Indiana, and released since then. The Illinois patient came into contact with the Indiana patient twice after his return from Saudi Arabia, and could have thus contracted the virus. While the Illinois patient never required medical care or hospitalization, he has been monitored closely by local health officials and CDC since his May 16 diagnosis.

When the Illinois patient was first tested for MERS on May 5, results were negative. Upon testing again on May 16, his test results were positive for MERS antibodies. While the patient was never sick to begin with, he says he is “doing well,” said CDC.

Between the Indiana and Illinois cases, the second case of MERS was diagnosed in Florida, in a 44-year-old man who arrived from Saudi Arabia on May 1. Admitted to the Orlando’s Dr. P. Phillips hospital on May 8, the hospital said he was “in good condition and continuing to improve,” as of May 12.

The virus has infected 572 individuals globally, with 173 deaths, according to CDC and the World Health Organization. The mechanism of transmission is still unknown, but appears to be predominantly through close contact with an infected individual. Symptoms of MERS include fever, coughing and shortness of breath.

“This latest development does not change CDC’s current recommendations to prevent the spread of MERS,” said David Swerdlow of CDC. “It’s possible that as the investigation continues, others may also test positive for MERS-CoV infection but not get sick.”

None of the three identified U.S. cases of MERS have developed life-threatening illnesses.