A place to be critical...

Around May/June 2015, the Middle East respiratory syndrome (MERS) coronavirus escaped its Arabian Peninsula bonds and exploded...still associated with the circumstances created under lax hospital conditions...into another part of the world entirely - South Korea.

About 20% of South Korean MERS cases were fatal. In contrast, nearly twice that proportion have died after MERS-CoV infection among 26 countries (36% fatal).[1] Meanwhile, a little over twice the SOuth Korea proportion of fatal cases occurs in the Kingdom of Saudi Arabia (KSA; 42%).[2] 

It is interesting to look at another possible measure of clinical impact - how often a MERS patient is publicly described via official channels as being in "critical" condition. I suspect that this term could be applied as arbitrarily as anything else used by humans, nonetheless, see the figure below.

Total MERS-CoV detections (mustard bars; left-hand axis)
and mentions of cases in "critical" condition (red bars; right-hand axis).
Taken from the MERS-CoV data visualizations page.[3]
Click on image to enlarge.

A few things:

• Sadly, you have to ignore the biggest peak - the Jeddah-2014 hospital outbreak (March to June) - as data during that time were rare and detail was mostly absent both from the KSA Ministry of Health and the World Health Organization
• If we look at the South Korea peak (May/June 2015) versus the most recent Riyadh outbreak (July/August 2015), there seem to be a lot more mentions of critical cases. There is also more red visible during the Eastern Region/Ar Riyadh region peak around January/February 2015. 

There may be little to conclude from observations such as this, but it is yet another interesting pattern to muse upon.  

Older males with comorbidities are heavily represented among MERS disease cases that present to hospitals (younger people among those with mild or no notable disease) and older  males and females with comorbidities among the fatal outcomes. A shared risk is that comorbidities are preyed upon by MERS-CoV.

Comorbidities include diabetes mellitus, cirrhosis and various lung, renal and cardiac conditions. All of these are diseases of concern among countries with abundant unhealthy food options, weight issues and ageing populations. Is your country one of those? Even familiar old viruses could re-emerge as threats to this subgroup as the years go by. In the meantime, emerging newly identified viruses create an atmosphere of concern.

MERS-CoV detections broken down by age bands and into total cases
(left hand graphs), and those with a fatal outcome (right-hand grpahs).
Taken from the MERS-CoV data visualizations page.[3]
Click on image to enlarge.

References..

1. http://www.who.int/csr/don/01-october-2015-mers-jordan/en/
2. http://www.moh.gov.sa/en/CCC/PressReleases/Pages/Statistics-2015-10-04-001.aspx
3. http://virologydownunder.blogspot.com.au/2014/08/mers-cov-daily-monthly-and-cumulative.html

MERS-CoV and the host: a serious disease of those with disease

Case total currently stands at 150 including 64 deaths (PFC of 43%), with the World Health Organisation's latest update adding in the recent death (their tally says 149/63) and the Oman case and a new death being reported from eastern Saudi Arabia. The details for this latest patient are (FT#152):

• 56-year old male
• Comorbidities
• Contact of a previous case.

So, as the Oman case showed, transmission from a previous case can lead to mild illness. The Qatari case before that showed that a contact can be asymptomatic. This latest fatality highlights that under the right pre-existing disease conditions, even a 2nd "passage" of virus from a human to another human, can lead result in death. 

It's a very much about the health of the human host who acquires the virus, as we've seen all along with MERS and also among cases of influenza A(H7N9) virus infection.

The latest WHO update also notes that...

Patients diagnosed and reported to date have had respiratory disease as their primary illness. Diarrhoea is commonly reported among the patients and severe complications include renal failure and acute respiratory distress syndrome (ARDS) with shock. It is possible that severely immunocompromised patients can present with atypical signs and symptoms.

Nearly half the Indonesians performing Hajj may be over 60-years of age

On top of that, a quarter may have underlying illnesses. This, according to an article on Arab News, is an estimate based on comments from the Indonesian Ministry of Health and Religious Affairs, Haj Health Center.

As we know, age and underlying diseases, or "co-morbidities", are significant risk factors for more severe disease following MERS-CoV infection.

These data give an the world an insight into one visiting population, does it hold true for other countries as well? If so, we get a snapshot of why public health officials are concerned for the health of their country's Hajj pilgrims in the coming months. MERS-CoV transmission efficiency may be low, but the clicnial impact from this gathering may be high.

Globally mobile at-risk population + site of most infections + little knowledge of basic levels of virus source/community load at that site = less than ideal situation.