Friday, 21 March 2014

MERS-CoV in camels... [CORRECTED]

The top pie chart shows the distribution
of all human cases containing the word 
"camel" in their case notes, by the site where
the human was likely to have acquired their 
MERS-CoV infection. The bottom bar 
graph shows those data in terms of the
 proportion of cases at that site for which
"camel" contact was possible.
Click on chart to enlarge.
Thanks very much to Nicholas Evans (@neva9257 via Twitter) for asking me to back up my gut feeling about there having been more camel-links among MERS-CoV cases outside the Kingdom of Saudi Arabia (KSA) compared to inside.

I live to serve and so using those data I have to hand I've made a couple of charts. I'll keep these updated from now on too. 

I'd be grateful if anyone wanted to shout out human cases where camel contact was mentioned. I currently have 8 in total on my list of 201 lab confirmed MERS-CoV cases. (see the figure up there for where my cases are sourced). There may be many I have missed though.

One obvious question arising from the bottom bar graph is why does such a low proportion of camel-associated cases occur in the KSA but not elsewhere

For the sake of simplicity, I'll exclude the possibility that MERS-CoV jumps off its camel hosts at a border. Because the latest 68M from UAE may well have acquired his infection while visiting his camels in the KSA I have now listed him as a KSA acquisition...until I hear differently). We also know that camels in the KSA get actively infected (see earlier posts, listed below, on these findings [1,2,4]). 

So do these charts, by highlighting that so few camel links are to be found in the KSA (site of >80% of MERS-CoV human cases), discount camels as a source of infection? I don't think so. We have some very compelling evidence for camels hosting MERS-CoV [4], for camels being present in mass gatherings [5], and nothing but an absence of epidemiology to counter their role as a host and source.

I suspect the graph shows that MERS cases in the KSA won't admit to camel contact. Alternatively, perhaps contact, in its many possible direct and indirect forms is not being adequately sought or listed in case reports and in "gumshoe epidemiology" efforts (Ian Lipkin's comment, [6]). But why would camel contact not be listed, reported or collected? Perhaps it is seen as a bad thing? There may be stigma associated with acquiring an illness from a camel. Or perhaps stigma attached to the way in which that illness was acquired.

Perhaps it is a simpler explanation. There is likely to be fear, or a real risk, of social and economic fall-out of "naming and-shaming" camels as a major source of infection/disease. Camels fill many important and significant roles in the lives of those around the Arabian peninsula; from food, drink, religion to tourism and fun. But not identifying camel links in the spread of MERS-CoV, if indeed more links do exist, won't stop KSA's locals from acquiring infection and MERS. 

If there is a deficit in reporting camel exposures in the KSA, for whatever reason, it does one thing particularly well; it delays the understanding of how to protect people and reduce their exposure to MERS-CoV. I think that understanding is probably inevitable, so it may be better for the KSA Ministry of Health to get out in front of the issue; be proactive in finding the source of infections and openly discuss and plan for the implications. But I may be seen as living in a world of unicorns and fairies (again) to suggest that will eventuate. My cynicism is based on 2-years and 201 cases of a virus that's been very well virologically and molecularly detected and characterised outside the KSA, while its basic aetiology and epidemiology inside the KSA has left much to be desired.

I would very much like some locals to weigh in on this topic. Here (in the comments below) or by email or on Twitter. The bar graph simply highlights a discrepancy that could be cleared up with a better understanding (perhaps just by me) of what may  underlie the difference in the apparent roles for camels among countries sharing borders.

References...

  1. Dromedary camels are a host of MERS-CoV...
    http://virologydownunder.blogspot.com.au/2013/12/middle-east-respiratory-syndrome.html
  2. Middle East respiratory syndrome coronavirus (MERS-CoV): camels, camels, camels!
    http://virologydownunder.blogspot.com.au/2014/02/dromedary-camels-are-host-of-mers-cov.html
  3. MERS in the UAE....[UPDATED]
    http://virologydownunder.blogspot.com.au/2014/03/mers-in-uae.html
  4. Dromedary camels are a host of MERS-CoV...
    http://virologydownunder.blogspot.com.au/2014/02/dromedary-camels-are-host-of-mers-cov.html
  5. Middle East respiratory syndrome coronavirus (MERS-CoV) cases rise in march: Festival-related?
    http://virologydownunder.blogspot.com.au/2014/03/middle-east-respiratory-syndrome.html
  6. Receptor for new coronavirus found: Virus might have many animal reservoirs.
    http://www.nature.com/news/receptor-for-new-coronavirus-found-1.12584