Wednesday, 14 August 2013

4.8-million Umrah pilgrims free of MERS-CoV...?

According to an Arab News reportthe Kingdom of Saudi Arabia's (KSA) Health Minister Abdullah Al-Rabeeah, has said that 4,800,000 pilgrims visited  to perform Umrah this year, and not one left having had a Middle East respiratory syndrome coronavirus (MERS-CoV) infection. 

That certainly suggests that the virus is hard to catch and that its not transmitting stealthily.

Wait...it doesn't mean either of those things. 

What it means, in case you were to misinterpret the headline, is that the disease, MERS (as opposed to the virus, MERS-CoV), was not diagnosed in those people. 

Wait, no, it means that a disease severe enough to be put on the radar for MERS testing, did not occur among the 4,800,000 pilgrims. Just a reminder from the World Health Organisation of what their interim definition of a probable MERS-CoV case looks like: 
excerpted form the 3rd July 2013 version
  1. A person with a febrile acute respiratory illness with clinical, radiological, or histopathological evidence of pulmonary parenchymal disease (e.g. pneumonia or Acute Respiratory Distress Syndrome)
    AND
    Testing for MERS-CoV is unavailable or negative on a single inadequate specimen
    AND
    The patient has a direct epidemiologic-link with a confirmed MERS-CoV case
  2. A person with a febrile acute respiratory illness with clinical, radiological, or histopathological evidence of pulmonary parenchymal disease (e.g. pneumonia or Acute Respiratory Distress Syndrome)
    AND
    An inconclusive MERS-CoV laboratory test (that is, a positive screening test without confirmation)
    AND
    A resident of or traveler to Middle Eastern countries where MERS-CoV virus is believed to be circulating in the 14 days before onset of illness.
  3. A person with an acute febrile respiratory illness of any severity
    AND
    An inconclusive MERS-CoV laboratory test (that is, a positive screening test without confirmation)
    AND
    The patient has a direct epidemiologic-link with a confirmed MERS-CoV case.
So really, only #3 would account for any MERS-CoV infection that wasn't at the severe end of the clinical scale (the tip of the iceberg as we all like to refer to it). But even then, a case has to be linked to another MERS-CoV case. 

In other words, less obvious cases - those infections that may look like a standard influenza-like illness (ILI), or be asymptomatic (both have occurred win MERS-CoV positive people) - would not get tested and we have no way of saying that these people were MERS-CoV free.


I'm sure that many of those 4,800,000 pilgrims had some respiratory symptoms during their time in the KSA - we know f
rom research papers that the 200 or so endemic respiratory viruses continue to circulate among pilgrims in the KSA during large gatherings.

It would be very reassuring to know how many cases of mild or moderate ILI respiratory infections were seen by a Doctor in the KSA and how many were tested for MERS-CoV by RT-PCR. A prospective study like that by Gautret et al which did not sample on the basis of signs and symptoms, augmented with some serology testing to show recent or past MERS-CoV infection but conducted by/at/for the KSA
, would be a great example. It would even pick up asymptomatic cases. Even without the serology component that would be a valuable good study.

I guess we'll just have to wait for the research paper.