Monday, 14 April 2014

MERS-CoV: Healthcare worker numbers are spiking...

One of several questions I have about MERS just now is whether there are in fact more healthcare worker MERS-CoV-positive cases occurring now compared to previously. It feels like there are.

Overall there are 50 HCWs listed in my database at writing. This is a database I maintain from official (WHO and the various Ministries of Health) data as well as FluTrackers' independent data collection; all of which are publicly available. For those who follow me, you will know that I often complain about the MERS data being incomplete. So take these charts as providing you with a good guide to the situation rather than an official document. You are reading a blog after all.

Click on image to enlarge
So here we can see a few ways of presenting the HCW figures. Let's step through them:

a) shows you the proportion of just HCWs with fatal MERS-CoV infection (PFC) and the proportion who survive (the majority; PSC)

b) identifies the PFC and PSC among all 242 MERS-CoV cases worldwide for comparison

c) reveals the proportion of all 242 cases MERS-CoV cases who are HCWs again, for comparison

d) shows you the a comparison of the proportion of all MERS cases that are HCWs (~21%) and the proportion of MERS-CoV-positive HCWs who died (~3%).

Click on image to enlarge.
So to look more closely at how HCW numbers have changed over time, and particularly how they have changed lately, I've created a chart tracking HCW numbers both cumulatively (the pink mountain with numbers on the left hand side) and as cases announced per week (the purple dots, with numbers on the right-hand axis).

Sure enough, we have seen a big jump in the number of HCW cases in just the past week. In fact, Week 108 (Week starting 7-Apr) has been the biggest week in the 2-year history of MERS-CoV [however, see my caveats about case dates from my post earlier today]

There were few MERS cases at all in 2012 but in 2013 they took off in April and peaked in September (I'll plot these numbers for comparison in my next post). Since May-2013, HCW numbers have been spotty without any obvious pattern...to me at least. 

So that leaves the questions of whether we are also seeing more asymptomatic cases recently and whether the age is trending towards a younger value?

The ultimate question of course is why are things changing?