Tuesday, October 20, 2009

"Very Sobering" Flu Season

Most everyone it seems is dismissing the H1N1 threat as overblown. Some go so far as to see government conspiracy. I am not among those in either camp. I have said in previous posts that while there is no need to panic, it would be foolish not to keep a close eye on this matter. The prevalence of the virus in the southern hemisphere these last few months and the fact it never "went away" as is the usual case in this country during sumer months were all potential red flags. Combined with a tendency to strike the healthy and a high virulence capacity were more casuses of concern.
This has recently come to the forefront in the mainstream media headlines but nothing has truly driven home the fact like the graphics from the CDC and the commentary from Effect Measure. Effect Measure has an excellent if chilling explanation of the charts (especially needed since the graphics are so poor) and excellent commentary as well. In a nutshell, this flu season is shaping up to be like few others and while a typical flu season may kill more in number, these are typically the old an infirm. H1N1 victims are more often, much more often, infants, children, teens and healthy adults. As Effect Measure points out, these could triple or even quadruple and not reach what a "typical" season involves. But the psychological effects of so many young and healthy would be immense.
Monday morning, start of week three of the official flu season (which began October 4). CDC's scientific spokeswoman on the flu, Dr. Anne Schuchat has said we are seeing "unprecedented" flu activity for this time of year, including an unusual toll in the pediatric age group. What does "unprecedented" mean? It's not very specific on what precedents are included, but if we confine ourselves to the three years before this one, we can get a good idea of just how unusual this flu season is.

CDC Source, full size here; legible on the .pdf version (page 8) (hat tip OmegaMom)
Weeks are on the horizontal axis. There are five age group panels (0 - 4 years at the top, seniors at the bottom) and at the right side of each panel you will see lines gradually ascending from week 40 (October) to week 20 (April), CDC's traditional flu season. Everything to left of week 40 in each panel is prior to or just after the official flu season and is essentially zero for the three prior seasons, .....

...The "unprecedented" year we are having shows up in the left of each panel. The rates are a solid line running across the bars. the bars are case counts (note to CDC: lose the bars. They are obscuring the picture). To see how unusual this is, look at the top panel (0 - 4 years), where the solid line has risen to 1.4 cases per 10,000 infants and toddlers in week 40 (first week in October). In the three previous years that seasonal risk level isn't reached until the 3rd week in January. We are 3 months in advance of the last three years by this measure, and the case count for that age group is still rising.

For the 5 - 17 year old panel the difference is more dramatic. We've already reached the risk level we would normally see for the whole flu season, and we are just getting started. That's the group being hit the hardest, and half the fatalities since September 1 have been in the 12 - 17 year old age group, confirming that.

For adults between 18 and 50, the picture is like that for the under 4 year olds: about 3 months in advance compared to the bad flu year of 2007 - 2008 and already exceeding that for the entire flu seasons of the other two years. This is the age group populating the ICU beds. Even though population rates may be smaller, there are many more of them. ...

...It is true that seasonal influenza kills a lot of people every year. They are mainly seniors, people like me. People care about seniors, of course, but our deaths are considered part of the natural order of things. Old people die. If it's not one thing, it's another. And of course our mortality rate is very high, compared to all other age groups. Even if the number of infants, children, teens and healthy adults double or triple or quadruple, the number of deaths may not ever reach what happens normally to seniors during seasonal flu, but the psychological and social impact is considerably greater. That's one of the fallacies in comparing the numbers of deaths from this flu with the usual seasonal flu. More

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