# 3496
Traditionally, influenza usually claims the lives of the elderly; those over the age of 65. In fact, 90% of the estimated seasonal influenza deaths each year occur among senior citizens.
Pandemic viruses, however, often demonstrate an age shifting away from the elderly and more towards attacking – and killing – younger patients.
The infamous `W shaped curve’ of the 1918 pandemic clearly shows that the death rates among those in their teens, 20s, and 30s was much higher than was normally seen in previous influenza years.
And once again, at least in the early going, we seem to be seeing this same pattern with the H1N1 swine flu. Relatively few infections or deaths are being reported in those over the age of 65.
We’ve heard a lot of optimistic, at times even dismissive talk that this virus is `no deadlier than seasonal flu’. While it is hard not to be heartened by the low number of fatalities reported so far, that doesn’t tell the whole story.
The impact of this pandemic may hinge more on who (meaning: what age cohort?) is being killed by this virus, than it will on the total number of pneumonia & influenza (P&I) deaths it generates.
But to talk about relative CFRs and the likely impact to our society we need a baseline.
How many deaths, and in what age groups, do we see in a normal year? What are we used to? What can we abide?
While we’ve discussed some of its limitations in the past, the best estimate we have on influenza-related deaths comes from the CDC, which calculates that roughly 36,000 Americans die as a result of the flu every year, and of those 90% are over the age of 65.
Flawed or not, these are the numbers against which the impact of this pandemic will be measured. So we might as well use them.
(Be warned: What follows are approximate numbers, and back- of-the-envelope calculations. They, hopefully, have probative value . . . but are not intended to serve as predictions)
Since 90% of these deaths are thought to occur in those over 65, conversely we `know’ that only 10% – or fewer than 4,000 deaths – occur in those under the age of 65.
In fact, if you are one of the 38 million Americans over 65, you have about 1 chance in 1200 of dying in an average year from influenza related illness.
38 million / 32,400 (90% of Ttl)= 1,172
Your odds go way down if you are under the age of 65.
Out of the 266 million remaining Americans under 65, only 3,600 usually succumb to flu-related illness each year.
Which means your odds of dying from the flu in that age group is just 1 in almost 74,000!
266 million / 3,600 (10% of Ttl) = 73,888
Comorbid medical conditions, diminished immune systems, and frailties of advance age can make the likelihood of dying from influenza in an average year as much as 60 times greater for those over 65.
(There is nothing `magical’ about the age 65, it is an artificial line of demarcation. Influenza death rates begin to increase in one’s 50’s and go higher the older you get.)
Pneumonia, in fact, was for centuries called `the old man’s friend’, since the elderly tended to succumb relatively quickly and painlessly to it.
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 impact often shifts disproportionately to younger victims.
None of these numbers should be taken as a prediction. I’ve no idea what the eventual attack rate, CFR, or overall mortality rate in society of this pandemic will actually turn out to be.
That isn’t the point of this little exercise.
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.
Which is why we need to remain vigilant over the summer, this fall, and winter and not trivialize or dismiss this pandemic.
We need to practice good flu hygiene all of the time; cover our coughs and sneezes, wash our hands frequently (or use alcohol sanitizer), and stay home when we are sick.
We need to be preparing our homes, our families, our businesses, and our communities to deal with whatever this virus brings us over our winter. For information on how to do that, you should visit www.flu.gov and www.ready.gov.
Everyone needs to have, or become, a `flu buddy’ to a friend, neighbor, or relative (see Pandemic Solutions: Flu Buddies).
Additionally, you can help your community by volunteering with the American Red Cross, The Medical Reserve Corps, CERT, or your Neighborhood watch.
As you can see, we aren’t helpless in a pandemic.
There are a great many things we can (and should) be doing over the summer to prepare that will help mitigate the impact of this virus.
Quite frankly, the odds say that most of us will come through any illness from this virus just fine. A week, maybe two of illness, and then recovery for probably 99% of us.
Good news, by any measure, and important to keep in mind.
But not everyone will be that lucky.
And we need to be prepared for that eventuality. As individuals, and as a society.
