# 3391
A little over two years ago the HHS released a pandemic severity index system for the United States. It categorized pandemics into 5 levels, with Category 1 being the weakest and Category 5 being the strongest.
To put things in perspective, the CDC estimates that in a normal flu season, 36,000 Americans die (indirectly or directly) as a result of influenza.
While this number may be flawed (it is derived from mathematical modeling, not an actual count), it is the benchmark against which pandemics are judged.
The assumption is that in a pandemic (any category), 30% of the population would fall ill.
That is an estimate, based on the data we have from the pandemics of the 20th century. In the UK, the government’s SAG (Science Advisory Group) has suggested that number could go as high as 50%.
The truth is, every pandemic is different, and no one really knows. But we need some numbers to plan from, and a 30% attack rate has been deemed reasonable by many planners.
This is roughly 3 times the number of people normally stricken in a year by influenza.
Which means that a virus with the same virulence as seasonal flu would have 3 times the impact, based simply on the increased number of people infected.
Three times higher absenteeism, three times as many hospitalized, and likely, three times the number of deaths. And many of those deaths will involve children and young adults.
No . . . not a Stephen King apocalyptic pandemic scenario, perhaps, but quite nasty in any event.
The greatest impact would probably be felt in the health care field, where a tripling of emergency room visits, hospital admissions, and the need for ventilators or ICU beds would constitute an enormous challenge.
During a normal `bad’ flu season, which we see every few years, these facilities are badly taxed by far fewer patients. Some hospitals are forced to temporarily suspend elective surgeries, and some emergency rooms have to close to traffic, simply because they are overwhelmed with flu cases.
Added to that would be a likely tripling of employee absenteeism due to the flu.
At a time when demand for services would be at its highest, the ability of these facilities to provide it would be at its nadir.
So while a Category 1 pandemic virus may prove no deadlier than seasonal flu, its impact can be significantly higher.
A Category 2 pandemic would have a considerably greater impact, even though the virus would still be considered `mild to moderate’ in severity.
If seasonal flu kills 1 in 1,000 (the CDC’s estimate), then a Category 2 pandemic virus might kill anywhere between 1 and 4 in 1,000.
Statistically, the odds of dying in a Category 2 pandemic are still pretty low, but the impact on society grows significantly.
Here in the United States, that could translate into anywhere between 90,000 and 450,000 deaths. Globally, a Category 2 pandemic could kill between 2 and 10 million people.
Two pandemics of the last century would probably have fallen into this category. The 1968 Hong Kong Flu was probably a weak Category 2 pandemic, while the 1957 Asian Flu was probably a moderate-to-strong Cat 2.
Just as with hurricanes (which use a similar scale), the higher the category, the more damage you can expect. The ultimate `viral storm’ would be a Cat 5 pandemic, such as we saw in 1918.
Luckily, that level of virulence in an influenza pandemic virus appears pretty rare. Recent history (the past 120 years or so) indicates that the lower virulence pandemics are more common.
The question before us is, what Category pandemic is Swine Flu?
And the answer is; We don’t know yet.
Having a scale is one thing, having the tools to measure the `viral storm’ is quite another.
And right now, our tools are meager at best.
In many ways it reminiscent of the way things were with hurricane forecasting when I was a youth, growing up in Florida. For those under the age of 50, it is probably difficult to comprehend how things were before the advent of the weather satellite.
Up until the early to mid 1960’s, the only way we knew there was a hurricane out in the Atlantic was from ship, island, and aircraft reports. Storms would sometimes get `lost’ for hours or even days, when they moved beyond land-based observations.
Instead of having 48 or even 72 hours warning of an approaching hurricane, it wasn’t uncommon to get only 12 to 24 hours warning. And as far as intensity was concerned, that was even less precise.
Our ability to monitor the virulence and spread of the H1N1 virus is pretty much in the same league.
We have a great many `blind spots’ in our global surveillance system, and so a certain amount of guesswork is required to figure out the strength of any pandemic virus.
Allowing that the H1N1 virus could change and become more (or less) severe, right now it appears that we can eliminate the higher pandemic categories from consideration.
If this virus had a 1% or 2% (or higher) fatality rate, even with the spotty surveillance available globally, we’d know it by now.
And it appears unlikely that the virulence rises to the level of a CAT 3 pandemic, either. Which, for now at least, leaves the bottom 2 categories in play.
And while the relative impact of a CAT 1 vs. a CAT 2 pandemic can be great, the measuring stick - the fatality rate (CFR) of the virus – need only change a little to move the pandemic from one category to the other.
At this point in time, we simply don’t have a global surveillance system in place that can tell us if this virus is killing 1 out of every 1,000 people it infects . . . or 2 or 3 out of 1,000.
Complicating matters, the CFR is likely very different from one community to another. What may turn out to be a CAT 1 pandemic in Ottumwa, Iowa could well end up being a CAT 2 pandemic in Buenos Aires.
Of course, the fatality ratio isn’t the only measure of a pandemic. The attack rate, the percentage of people affected by the virus, can be every bit as important.
According to the Utah Health Department’s website, in their June 24th Situation Report, the CDC is working under the assumption that the H1N1 virus will spark a CAT 2 pandemic.
This doesn’t appear to be a determination, only an estimate, and according to the press release, the CDC is watching events in the Southern Hemisphere closely for validation of that estimate.
This would be in line with what we’ve seen to date. Something on the order of the 1968 or 1957 pandemic.
Whether it will trend towards the weaker 1968 event, or ramp up this fall to a 1957 style pandemic is impossible to know right now.
And of course, some places may see a greater or lesser event.
The Deseret News this morning has a statement from the Utah Health Department that sums up things pretty well. A hat tip to AlaskaDenise and Colormyquilt on Flutrackers for these links.
"The public remains our most important partner as we respond to this developing pandemic," said Dr. David Sundwall, health department executive director. "One thing we can be sure of is that this virus will continue to change over time and we want to make sure Utahns don't let their guard down in terms of protecting themselves and others."
Officials continue to monitor any changes in the severity of illness that those who contract the virus are experiencing. They are concerned that it may become more virulent in the fall and spread more widely as cold weather begins. If that happens, Utahns may be asked to take additional steps to limit its spread.
"Families should begin preparing for what they would need if they are asked to spend a week away from school, work or other activities. Now is the time to update, or create, your emergency stockpile. Items like food, water, tissue, sanitizers, over-the-counter medications and prescription medications are all useful items to have on hand in the event you become ill and are confined to your home," officials said in a press release.
Good advice, and not just for the people of Utah.
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