The contact investigation for the Indiana patient who was the first case of MERS in the United States revealed a positive blood test result on May 16 for MERS antibodies in a business associate living in Illinois. The discovery is significant for two reasons. First, the Illinois resident had only mild, cold-like symptoms and CDC respiratory testing on May 5 did not uncover an active infection. This indicates that MERS may cause a broader spectrum of illness than was previously associated with the virus. Second, the contact between the Indiana patient and the Illinois resident was extended, consisting of handshakes and two business meetings within six feet while the patient was exhibiting symptoms of MERS. This indicates that person-to-person transmission of the virus is possible outside of healthcare and family settings that are considered high risk for transmission.

“This latest development does not change CDC’s current recommendations to prevent the spread of MERS,” said David Swerdlow, M.D., 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. Along with state and local health experts, CDC will investigate those initial cases and if new information is learned that requires us to change our prevention recommendations, we can do so.”

The Illinois resident is currently in self-isolation until further test are completed and the CDC has expanded its contact investigation to include those of this individual. CDC has tested more than 50 people as part of the contact investigation for the Indiana patient. All other tests have been negative. Further, the Illinois Department of Public Health reported on May 19 that additional testing through oral and nasal swabs of the Illinois resident indicates no current infection, meaning this individual is not capable of currently spreading the virus.

Currently, the World Health Organization does not include patients with a positive blood test for MERS antibodies in its case definition for MERS. Therefore, the Illinois resident does not officially qualify as the third case of MERS in the United States or the first non-imported case. For the purposes of the contact investigation, CDC is treating the positive test result as evidence of a third infection.

For more information:

• CDC press release
• CDC transcript of the press briefing
• Illinois Department of Public Health press release – Negative test results indicate that Illinois resident is not able to spread MERS
• Illinois Department of Public Health press release – MERS Hotline