The very recent death of Dr. Zhang Xiaodong, a 31-year-old surgeon at the Shanghai Pudong New Area People’s Hospital and a number of younger sufferers has raised the spectre that the Avian Influenza A(H7N9) might be morphing into something more deadly in 2014 (as compared to 2013) and only if you listen to mainstream media which is often too quick to push the panic button.
Knowing the go-to people on this subject I thought I’d do some reading.
Via his excellent Virology Down Under blog Ian Mackay, PhD (with the Australian Infectious Diseases Research Centre at the University of Queensland) wrote a piece about this very subject just last week. H7N9 age with time: is a younger adult demographic emerging this time around? Excerpt:
This is a big graphic – sorry for that – but I thought it best to show the distribution of age bands (this is updated from the paper I co-authored recently with Joseph Dudley) alongside the shifting age in total numbers and proportion of cases each week. The data are all publicly sourced and verified against the WHO and scientific literature whenever possible and of course, against FluTrackers excellent case list.
The chart below (click on it to enlarge and see much more clearly) then some comments underneath. Keep the previous sex/week chart in mind (it’s trend has not changed much with the latest cases; these charts also result from a question from CIDRAP’s Lisa Schnirring last Saturday) when looking at this. Is any effect seen below due to the increased female representation?
I’m quite an admirer of Ian’s work, especially those graphs looking at accumulation/epidemiological data. I couldn’t help but notice that his Age Band chart uses a standard 2D column graph rather than a 2-way bar graph as used by demographers. I thought the use of that methodology along with a graph showing the decline in average age since October 2013 might be a better illustration of his very sound reasoning.
So, to add emphasis to Ian’s article I spent last night updating my H7N9 data, untouched since early December and did a couple of new graphs up to and including case number #216 (sourced from FluTrackers).
The first graph is an age pyramid (otherwise known as a beehive graph) commonly used by demographers and health experts to map population and mortality distributions. As you can see by using this methodology I’ve been able to bring the population groupings to just 5-year intervals which highlights the continued concentration of male onsets (70.2%). Of interest also are the aged cohorts with the highest percentile of cases with 55 – 59 (21-male/5-female/12.1%), 65-69 (19-male/5-female/11.2%) and 50-54 (13-male/10-female/10.7%). These three groups alone make up more than a third of all H7N9 onsets to date.
The second chart shows the average age of all onsets since case number #2 through to case number #216 (minus one case which does not come with age data). Interestingly, the first two victims were aged 87 and 27, thus the average age from those two was 57 which is in the variable range of the virus through its entire 11-month history. As you can see from the coloured section which represents all onsets from October 2013 (effectively, the second wave of H7N9) the average (or mean) age has reduced by approximately two-years. According to my data, the average age for onsets for wave 1 was 57.0 while currently for wave 2 it sits at 52.7.
For the record I am by day a post graduate student and a Workforce Planner. In terms of medical knowledge at best I am a keen amateur epidemiologist who gained an interest in the subject having worked in an Operating Room Suites as an Anaesthetic Secretary a decade ago.
I hope this small piece and further blogs during 2014 (time permitting) adds to the H7N9 discussion be it by an additional or improved data point, analytic or infographic.