North America appears to have seen its first case of onward transmission of the MERS virus, with the Centers for Disease Control and Prevention announcing Saturday that a contact of the first U.S. case has developed antibodies to the virus.
An unidentified man from Illinois, described as a business associate of the first U.S. case, appears to have been infected with the Middle East respiratory syndrome coronavirus, the CDC revealed during a hastily called news conference.
The two men met for between 30 and 40 minutes on April 25, and again briefly the next day. They reportedly shook hands during the meetings.
Officials at the World Health Organization and the CDC have stressed the MERS virus does not currently transmit easily from person to person. They have suggested that close and prolonged contact may be need to pass the virus from an infected person to one who is healthy.
When pressed to explain how transmission during a business meeting was consistent with that pattern, the CDC's point person for MERS virus, Dr. David Swerdlow, said the two men had face-to-face contact within a range of about two metres.
"We still don't think that this virus transmits easily, but it does transmit," Swerdlow said. "And that's why we've been concerned all along."
Swerdlow acknowledged that little is currently known about how the MERS virus is spread. Questions remain about who is likely to transmit virus — only severe cases or mild infections too? — and when during an infection a person can transmit the virus.
Still, he suggested this case hasn't led the CDC to rethink its ideas about the risk of MERS virus transmission.
But an infectious diseases expert who has been following the MERS situation closely said it should make public health officials think twice before rushing to assuaging people that the risks posed by the MERS virus are low.
"We in public health have to take a step back and not be so reassuring to the public that the chance of transmission is actually very small," said Dr. Michael Osterholm, director of the Center for Infectious Diseases Research and Policy at the University of Minnesota.
"One case does not change the overall risk picture here.... But it should give public health a real cause to pause its message that this is hard to transmit."
Osterholm also lamented the fact that answers to the transmission questions are still not available, even though the virus has been infecting people for at least two years. The first known cases occurred in Jordan in April 2012.
"One of the unfortunate situations here is that for more than a year we've been calling for the kind of epidemiologic studies that would give us a better handle on this very kind of information. Who is it that's most likely to transmit? And who is most likely to become infected?" Osterholm noted.
"We don't understand who will transmit this virus and where and how do they do it."
Many of those calls for studies have been directed to Saudi Arabia. With the lion's share of MERS cases, it is best positioned to do the type of research that would answer key questions about where the virus comes from, how people are becoming infected and to flesh out the dynamics of human-to-human spread. But so far the country has not undertaken some of these critical studies.
To date there have been over 600 MERS infections in 19 countries; roughly 180 of those cases have been fatal. All cases trace back to several Arabian Peninsula countries, most notably Saudi Arabia and the United Arab Emirates.
Swerdlow said public health officials are now investigating family members and contacts of the man from Illinois to see if any have experienced symptoms that might be MERS infection. He could not put a number of how many people the investigation encompasses.
At the time the two men met, the first case was already feeling unwell. The man, an American doctor, had travelled a couple of days earlier from Saudi Arabia where he lives and works, to Munster, Ind., where he has family.
Swerdlow would not reveal the second man's age, occupation or the municipality in which he lives. The man had some mild cold-like symptoms in the days after the meeting, but is now described as well. Swerdlow said the man has been isolating himself since May 3 at the request of health officials, as a precaution.
At the present time the man from Illinois is not being called a MERS case. Swerdlow explained that the WHO's definition of MERS infection requires that a person test positive for signs of the virus during infection. The Illinois man tested negative.
Follow-up blood testing showed he developed antibodies to the virus, which is a sign he was infected.
There have been other instances outside of North America where people believed to have contracted MERS only tested positive with antibody tests. The WHO currently classes them as "probable" MERS infections.
Swerdlow said the CDC will be discussing with the WHO whether the case definition should change. But he acknowledged that different laboratories use different antibody tests, which makes it hard to standardize test results.
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