Wednesday 5 February 2014

H7N9 snapdate: age with time

Click on image to enlarge.
Age groups selected to convey clearest trends
without too many lines.
A quick look at some age bands followed each week during the course of both waves of the avian influenza A( H7N9) virus outbreak.

The interesting line to watch is that of the youngest age group (0-19-years) which has lifted to comprise 50% of cases in the week beginning 27-Jan. Also, the proportion of cases in the oldest age group (70->90-years) has dropped down in the past 2 weeks. 

There have been a rash of children in recent announcements; 8 of the last 45 cases have been <10-years of age. For a virus with a median case age sitting at 58-years, this is quite a departure. 

Is this due to an increase in familial clusters? Does it herald a shift in the way the virus is spreading? Intrafamilial transmission may provide a hint at increasing transmission efficiency. It might also be a sign of increased testing augmenting clinical observation of close contacts of ill family members. 

It bears watching closely whatever is happening because its different for some reason. Also worth watching is the downward creeping age. In 2013 the median age was 55.5-years and in 2014 it is 53.5-years. Among the past 45 cases it sits at 52.0-years

Tonight we have 310 H7N9 cases ( a third in Guangxi province bordering Vietnam has just popped up while I was writing this paragraph and I've altered the numbers above), with at least 50 deaths (that can be accounted for using public data).

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