Thursday, 3 September 2015

Where do these 'primary' MERS cases come from?

I was just dropping by the General Directorate for Infection Prevention and Control's Middle East respiratory syndrome (MERS) statistics website ([1]; Kingdom of Saudi Arabia) and noticed this graph which I've snipped and labelled below.

What strikes me as very strange is the listing of so many "primary" MERS cases (green). Keep in mind that the Command and Control Center of the KSA Ministry of Health has a case definition that does not allow for a person who has no symptoms as a Case-even if they are laboratory confirmed as being infected [2]. A strict clinical-based definition. In a more real-world definition for reporting a MERS Case, the World Health Organization (WHO) has, since at least July 2014, included any laboratory confirmed person (which includes suitably serologically confirmed) as a Case. 

In other words, the green bars represent KSA-defined Cases that have not acquired MERS-CoV infection from family, friends or house mates (yellow), not from healthcare workers or the healthcare facility (nosocomial; red and purple) and that are not unclassified (magenta). 

Excerpted figure from the General Directorate for Infection Prevention and
Control website.
[1]
Blue labelling by me using Photoshop.
Doesn't that just leave camels? 

But camel exposures are not being listed in WHO Disease Outbreak News (DONs) in anything like that number. It's very rare to see a camel contact listed in the current Ar Riyad province outbreak at all (just one, early on).

So where do these primary cases acquire their infection from?

Reference...

  1. http://www.gdipc.org/mers-stat.html
  2. http://nebula.wsimg.com/9e5c08742ca99231959e266fe5e46ee0?AccessKeyId=56AE5CCCF0799F235A2E&disposition=0&alloworigin=1