(ABC News) -- The deadly MERS-CoV virus has spread to a third U.S. citizen and officials believe the man was infected while in the U.S.
Officials from the U.S. Centers for Disease Control believe an Illinois man likely contracted the disease from an Indiana man, who became infected with the disease while working as a health care worker in Saudi Arabia. CDC officials said the two men met for two business meetings in Illinois before the original patient was found to be infected with MERS Co-V.
According to the CDC, the Illinois man had very mild symptoms that resembled cold or allergy symptoms and did not seek medical treatment.
The newly reported patient actually tested negative for an active MERS infection on May 5, but a follow up blood sample tested on May 16 found that he had antibodies to the virus, suggesting he had been infected with the disease.
Dr. Richard Besser. ABC News chief health and medical editor, said the indication that the virus can transmit between people, even when no symptoms were present, was interesting but not surprising.
“With most (if not all) infectious diseases, there is a spectrum of disease following infection, ranging from asymptomatic transmission to full-blown fatal disease,” said Besser. “While we don't know the full extent of contact between the two individuals, it does suggest that transmission is possible through somewhat casual contact.”
The CDC is not expected to issue a travel ban related to MERS, but advises people to alert their medical provider if they become sick within 14 days of visiting the middle east.
"This latest development does not change CDC's current recommendations to prevent the spread of MERS," said Dr. David Swerdlow, who is leading CDC's MERS-CoV response. "It's possible that as the investigation continues others may also test positive for MERS-CoV infection but not get sick."
In addition to the two men in Illinois and Indiana another man in Florida was found to be infected with the disease, after traveling to Saudi Arabia as a health care provider.
The outbreak of the MERS-CoV virus, which stands for Middle Eastern Respiratory Syndrome Coronavirus, has been concentrated in Saudi Arabia, where it was first reported. According to the CDC as of May 16 the virus has been found in 15 countries and a total of 572 laboratory-confirmed cases have been reported. Of those infected, 173 people have died.
The disease can lead to acute respiratory illness, fever cough and difficulty breathing. The virus spreads from person-to-person though close contact, but might also be transmitted to humans from animals, according to the CDC. There is no known cure or vaccine.