Wednesday, 27 November 2013

MERS-CoV by the numbers: recent weekly case activity...

Click on image to enlarge.
Confirmed MERS-CoV cases including 
fatal infections (green) and deaths (red) 
each week. Case numbers are listed on the 
y-axis (side), days of each week  along 
the x-axis (bottom). Case dates are 
derived from announced date of onset 
but if absent, on the date of reporting. 
Deaths are listed by date of death.
This follows on from my previous post (you can track links to earlier weekly charts) about lab-confirmed Middle East respiratory syndrome coronavirus (MERS-CoV) cases, plotted by week.

Approximately 85% of all cases have come from the Kingdom of Saudi Arabia. Around 63% of all cases with sex data are male (1:1.73, M:F). Among the fatal cases with data it's 75% male (1:3.06, M:F).

I've added in some previous charts because as the new cases and case details appear, so do the placement of the cases alter slightly. Hopefully, with WHO doing such a good job in providing details, these graphs will solidify and we can move on in the next post. 

I've marked in the Hajj week and the 14-day outer limit of the incubation period. Nothing much to see from that; no spike in cases, even after time has passed to allow the case data to catch up.

My tally suggests 161 cases (still awaiting the Spanish case to be confirmed or not) with 68 deaths, a proportion of fatal cases sitting at 42%.
A couple of things stand out to me from these charts...
  1. What is the lag between illness onset and MERS-CoV case announcement like? For example the recent 37-year old man who died was reported on 20-Nov, but became ill 9-Nov. Obviously there is time required to reach hospital (13-Nov) and then be tested and re-tested [confirmed] but this case died 18-Nov and was not reported as MERS-CoV case for 2-days. The case before that, a 65-year old man became ill 4-Nov, was in hospital 14-Nov and was reported 19-Nov. Before that the 73-year old woman became ill 13-Nov, hospitalized 14-Nov, died 19-Nov and was also reported 19-Nov.
    I presume that this indicates there is no active MERS-CoV PCR screening of influenza-like illness, but rather for  in the Kingdom of Saudi Arabia?
  2. There have been 5-8 fatal cases per month since June and 16-25 cases per month in total. However, with that lag, there may be more to come from November. 

In particular, point #2 makes me wonder if the KSA is settling in to stable (albeit very small numbers of total cases) transmission or acquisitions of MERS-CoV?