October 13, 2005

Misunderestimating "Captain Trips"

According to an article in the 10/12 Raleigh News & Observer titled "N.C. flu plan needs checkup," reporter Amy Gardner notes in her opening paragraphs:

The potential for a catastrophic flu outbreak has public health leaders worldwide reviewing how ready they are. In North Carolina, the bottom line is the same as nearly everywhere else: A pandemic would overwhelm the state's health care system.

With a shortage of hospital beds and vaccines, the state would struggle to treat the sick in a worst-case epidemic infecting 1 million North Carolinians, hospitalizing 25,000 and killing 5,000.

Wait just a minute. 5,000 dead?

The numbers cited by Gardener came from the N.C. Division of Public Health's Pandemic Influenza Plan.

The NC DPH begins its report by admitting it was calibrated using obsolete data, basing their population data on 1999 NC population figure of 7,425,183, and readily admits that these figures are substantially off by approximately 1 million residents. This concurs with 2004 US Census Bureau estimates, which states North Carolina had an estimated population of 8,541,221. Acknowledging that your base numbers are wrong to begin with doesn't exactly inspire confidence.

Based upon woefully outdated population figures, the DPH actually cites a worst case scenario (PDF) of nearly 1.4 million North Carolinians infected and requiring outpatient visits, 30,631 hospitalized, and resulting in the deaths of 6,994. The figures cited by the News and Observer story above were actually mid-range figures from the same report, not the worst case as the article claims.

With a rough calibration taking into account the 15.044-percent jump in population from 7.43 to 8.5 million, more accurate numbers are probably that same percentage (15.044%) higher.

A worst-case scenario flu pandemic based up these figures with a 35% infection rate claims to kill fewer than 11,000 North Carolinas, or something in the neighborhood of 0.129-percent of the total North Carolina population.

This is what we are afraid of?

Not quite. These are estimates based upon one software model that I am highly suspicious of, as history shows us something else entirely.

The closest-known relative of the H51N avian flu we currently fear is the H1N1 Type a Influenza virus responsible for the 1918-19 pandemic.

Overall infection rates of the 1918 Spanish flu pandemic were 20-30 percent of the overall population. Global mortality rates from the 1918 Spanish Flu pandemic ranged from 2.5-percent to 5-percent of the infected population.

Figuring a 20-percent infection rate in a population of 8.5 million, and a minimal mortality rate of 2.5-percent of the infected population, we are looking at 42,500 dead, not 5,000.

I may be wrong on the math. It has been consistently been my worst subject throughout my educational career.

That said, I cannot understand the huge apparent discrepancy between the anemic pandemic forecast by the NC Division of Public Health, and the historical example of the last major Influenza Type A infection seen in the Spanish Flu of 1918.

Comments and a thorough debunking are encouraged. I'd be thrilled to be wrong on this one.

Note: "Captain Trips" was the nickname of a weaponized super-flu that escaped a military weapons lab and killed 99.6% of Earth's human population in the 1978 Stephen King opus, The Stand.

Posted by Confederate Yankee at October 13, 2005 01:23 AM | TrackBack

Your math is correct, 42,500 with the basic assumption there has been NO advances in medical science over the last 88 years that would reduce the mortality rate. But then you are using the least case scenerio 30% and 5% would give a level of ]

Posted by: Dan Kauffman at October 13, 2005 07:35 AM

Your math is correct, 42,500 with the basic assumption there has been NO advances in medical science over the last 88 years that would reduce the mortality rate.

There is a reason I didn't factor in medical advances, and that can be summed up in two words: "Surge capacity."

The medical system has a finite amount of physical resources, and these resources are not designed for mass casualty events of any sort, especially not on the scale of a pandemic. If the forecast pandemic hits with the speed and distribution expected, the medical system will (most likely) be completely overwhelmed.

Posted by: Confederate Yankee at October 13, 2005 08:14 AM

Surge capacity may bring the rate up a bit, but not several percentage points. The nation as a whole is healthier, since then we've also started inoculating the general public with vaccines going to those most susceptible to the virus. From the research I’ve seen and the doctors I’ve talked to the virus that caused the pandemic of 1918 has for all intensive purposes been rendered impotent.

Right now it’s a minor issue and the virus will have to mutate slowly to maintain its full strength, it will take several years before it can effectively be transmitted from person to person. In which case experts all say a vaccine will be readily available.

Or it may become intertwined with another strand of the flu that can be readily spread from person to person; however it will suffer a distinct drop in its virility (punny huh?).

Either way, there’s much ado about nothing. If there isn’t a breakdown in the supply chain of the flu vaccine we shouldn’t have a problem. Remember last year when we had the break down in the supply chain, and there was a virulent strain of the flu virus running rampant that was going to kill millions in the US alone. Yeah I don’t remember the death counts being that high.

I blame Bush.

Posted by: phin at October 13, 2005 11:00 AM

I'm not sure you understand the huge limitations low surge capacity has during a mass casualty event such as a pandemic.

Use the 150 ventilators example from the N&O article.

You have 150 ventilators. Patient 151 that requires a ventilator to live. He doesn’t get one. He will likely die.

The problem with a pandemic is that you won't need just 151 ventilators at a time, you'll need 1500, or more, in a matter of just a few days. Anyone beyond that 150th person is likely to die. Likewise, UNC Hospitals has a less than 700 bed capability, and thousands are expected to need hospitalization at once, meaning many people will have to be turned away.

The current avian flu (H15N) when it makes the jump to capable of being spread human-to-human, will spread at a much faster rate than the 1918 flu. The 1918 virus circled the globe in less than a few months, even with the relatively primitive transportation systems they had at the time (primarily land transportation, often still relying on isolated rail services, foot, horseback, and ships). We now have subways, interstate highways, and commercial aviation. Instead of months, the virus could circle the globe in just weeks, and if 1918 can be a guide, it will run its course so fast that it will be over before it can substantially mutate and weaken.

The vaccine cannot be developed until the virus mutates until a human-transmissible form, either by shift or drift. You want to guess how long it will take to create a vaccine for the newly emergent strain, and make it commercially viable?

4-6 months.

Just after the pandemic has run its course.

Posted by: Confederate Yankee at October 13, 2005 12:17 PM

Your math is fine, but from the CDC website, the estimated mortality rate of Avain Flu (strain H5N1) is approximately 50%. Fifty percent.

If this bug mutates, which viruses do all the time, to an human-to-human airborne transmittable virus, then g-d only knows what we'll see.

Q: Are medical advances since 1918 offset by the speed and frequency world travel?

Posted by: yeti at October 13, 2005 01:07 PM

We don't have a single reliable number of the illegal aliens in this country at any given time. Any one of these folks could be carrying more viruses than we could possibly identify, in any time necessary to develope a vaccine. Wash your hands, purify your water, eat healthy, and don't wait for big government, they will bury you, when they get around to it!

Posted by: Tom T at October 13, 2005 08:31 PM

Yeti, I read somewhere that when it comes to the flu the modern medical advances made really offer little difference in the outcome...mainly because it is viral and not bacterial.

Like the 1918 avian flu, this pandemic is projected to hit the 20-40 year old "healthy" group the hardest.

Posted by: Maggie at October 13, 2005 08:38 PM

I wonder what IS the surge capacity of the health care system in NC

When we look at the numbers

42,500 to 127,500 they seem overwhelming and I by no means want to discount such a level of human suffering, but about 80,000 people die every year in NC and a lot of people get sick but don't die. We may be strained if we get hit, but we might not be helplessly overwhelmed.

I wonder what the number of beds in treatment centers IS? Hospitals Clinics etc and the numbers of care givers? Nurses Docters, EMTs?

Posted by: Dan Kauffman at October 14, 2005 12:55 AM

Information on hospital beds, numbers of hospitals, medical clinics , nursing homes
and nursing home bed with other information for different states can be found here.

Quick glance there seem to be 23K hospital beds in 113 Hospitals and 40K nursing home beds, and maybe a hundred or so rural clinics.

Posted by: Dan Kauffman at October 14, 2005 01:05 AM


80,000 people die each year in NC, but with a pamdemic, we're talking double that amount of hospitialization (based upon a 20% infection rate of 8.5 million people... and I'm not including the hypochondriacs and "just in casers" who will help clog the system) in one or two weeks.

If there are approximately 23,000 beds, and normal illnesses have them 2/3 to 3/4 full, and you slap 170,0000 flu victims on top of that, and you've got major surge capacity issues.

These things trigger mass graves for a reason.

Posted by: Confederate Yankee at October 14, 2005 07:01 AM

Yes it will be a State of Emergency for certain.

There are however 300K employed in the Health Industry. I would hope that non-essential businesses and schools would be closed. So ALL non-life threatenig medical treatments should be off the books. Schools have kitchens and mutlple bath rooms and if they are not being used would make good triage centers. It would be a mess but suvivable.

But the same thing could be happening in every State so the only effective responce would have to be local

Posted by: Dan Kauffman at October 14, 2005 08:43 AM