On May 17, the Centers for Disease Control held a teleconference and revealed that an Illinois resident had tested positive for exposure to MERS. The patient had been in contact with the patient from Indiana who first brought MERS into the United States. The Illinois patient was not ill but had MERS antibodies which showed that he had been exposed to the illness.
Middle East Respiratory Syndrome (MERS) is a serious respiratory illness caused by a novel corona virus called MERS-CoV. The illness was first diagnosed in 2012 and has remained largely confined to the Arabian Peninsula and the Kingdom of Saudi Arabia. In May 2014, two cases of the illness were detected in travelers from Saudi Arabia to the United States. One was in Indiana and the other was in Florida.
There are two tests for MERS. The first, called a PCR, tests a patient's respiratory secretions and would reveal any active illness. The second tests a blood sample from the patient and shows any antibodies for MERS-CoV. That would indicate a prior exposure to the virus at some point in the past. The Illinois patient had a negative PCR but a positive blood test.
The Illinois patient had two meetings with the Indiana patient before that patient was hospitalized. He may have shaken hands with the Indiana patient. The CDC states that no one else in those meetings appears to have become infected. The Illinois patient has no recent history of travel outside the country that could account for an exposure to MERS.
Both the Indiana and Florida cases of MERS are considered imported; i.e. they were acquired outside the U.S. The patient in Illinois is a locally acquired illness, and appears to be the first such in the country. Since the evidence of infection is blood work alone, he does not meet the official definition of a MERS case. That is a distinction which is important to public health officials but less so to the general public.
Dr. David Swerdlow of the CDC had this to say about the meeting between the Indiana MERS patient and the Illinois patient:
this person had face-to-face, close contact within six feet for over 30, 40 minutes. Again, we are trying to learn more about how this virus is transmitted and that's why we're doing these investigations and that's why we're reporting this. Again, we have had hundreds of other contacts and at this point certainly we'll be learning more in the future but at this point there's no evidence of transmission. So we still don't think that this virus transmits easily, but it does transmit and that's why we've been concerned all along.
Later in the teleconference Swerdlow stated that the two men had a second, briefer meeting, and that the two had shaken hands. The doctor did not know if the two had hugged, as is common in Middle Easter cultures.
The Indiana patient is believed to have had "close contact" with "53 healthcare workers, six household members, and this one business associate...". All have tested negative by PCR. Blood testing of these contacts has begun. The Illinois patient is in voluntary self-isolation at home until cleared by the CDC.
There was a great deal of push-back from the media during the teleconference. Most had the understanding that the term close contact mean that between health care providers and patients or between family members. Several were emphatic that the description of the meeting was not what the CDC had called close contact in the past.
What does it mean? This third case of MERS emphasizes that the CDC and other public health authorities are still uncertain about how the illness spreads from patient to patient. It also suggests that "close contact" need not be all that close. The blood work being done on all the contacts of the first two MERS patients and the contacts of the Illinois patient will show if anyone else developed MERS antibodies and might have been infected with few or no symptoms.