Age Shifting and Pandemic Mortality

[indigo girl]

http://afludiary.blogspot.com/2009/07/age-shifting-and-pandemic-mortality.html

Since the novel H1N1 virus has thus far (and for unknown reasons), infected and killed mostly those under the age of 65, it would seem more sensible to compare its fatality rate to what we normally see in that age group.

When we talk about the CFR (Case fatality ratio) of influenza, we are really talking about the fatality rate among those infected by the virus, not deaths in society as a whole.

The CFR is a less precise number than it might first appear since so often clinically mild or asymptomatic infections go uncounted. Any truly accurate number is pretty much impossible to calculate.

But, accurate or not, the number we repeatedly hear for seasonal flu is .1%, or roughly 1 person in 1,000 who gets influenza dies as a result of its complications.

And that is averaged across all age groups.

Roughly 90% of those fatalities are over 65, and have other medical issues. The CFR in the elderly is no doubt much higher than the .1% average.

Among those under 65, the CFR is a fraction of that - perhaps 1 in 10,000 (or even less).

And that is what we are used to as a society. That if you are under the age of 65, your odds of dying from influenza are pretty remote.

Imagine if, instead of this influenza claiming 90% of its victims over the age of 65, it age shifted so that nearly half of its mortality occurred in those under 65?

Suddenly a `seasonal' CFR rate of .1% (or even less) begins to look a lot worse. Particularly when you consider the increased attack rate (estimated to be 2 to 3 times that of a normal influenza season) during the opening years of a pandemic.

Instead of losing fewer than 4,000 Americans under the age of 65 in a flu season, we could be looking at losing 40,000 or more. Many of whom are likely to be children, or young adults.

This is the reality of a pandemic.

The point is, It doesn't take a high CFR pandemic to create a high impact on our lives, our society, and our economy.

And personally, I fear we are making too much of the low CFR, and not enough of the impact the loss of younger victims would have on our society.