Centerfield

I agree with the general tenor of your remarks (I've seen one expert, though I can't recall where, saying that the death-toll from the Spanish Influenza pandemic just wouldn't happen today because of intravenous hydration) but I don't think your reasoning about influenza "having had almost a century to and mutate into a sufficiently broadly fatal form to get through modern flu defenses" is sound. It's generally accepted that evolution favors diseases becoming *less* lethal, not more; dead hosts severely curtail the ability of the disease to spread. That's why lethal plagues almost always are diseases introduced from a new source (contact w/ a new culture, or transmission from a different species), rather than a mutation of a disease that's long been prevalent in the population. So identifying a new disease that can be transmitted from animals to humans is worrisome, because that's precisely the kind of thing that may start out with a high lethality. On the other hand, in keeping with the theory of diseases becoming less lethal as the mutant strains that don't kill the host reproduce better than the ones that do, there is evidence that is already happening in Viet Nam.

All flus are not equal.

That says to me that influenza has had almost a century to try and mutate into a sufficiently broadly fatal form to get through modern flu defenses, and has failed that whole time. That makes it pretty unlikely.

Have you seen or read Jurassic Park? One of the important theoretical points, at least in the book, is that "unlikely" and "only a matter of time" are essentially synonyms over the longer haul.

Undoubtedly the modern industrialized nation is in a better healthcare situation to deal with an epidemic than anyone was in 1918. So, yes, of course, we have that going for us. But is that license to not worry? Only if the not worrying is nevertheless accompanied by diligent scrutiny and preparedness.

Since bird flu is the buzz, let's talk bird flu. Bird flu has a pretty high mortality rate right now, but has yet to show the ability to be spread from human to human. If and when that happens, experts have speculated that it will very likely have mutated to a form that has a markedly lower mortality rate. This leaves the question of what sort of infection rate and death rate could have very serious effects on our lives, on our nation. If bird flu becomes widely spread, even with a mortality rate of 3-5 percent, I think the emotional and economic consequences would be quite substantial, even severe. People would stay home in droves, and we could run into panic shortages and looting, as people huddled in their homes watching CNN and Fox skeleton crews and perseverating about the apocalypse.

influenza has had almost a century to try and mutate into a sufficiently broadly fatal form to get through modern flu defenses, and has failed that whole time. That makes it pretty unlikely.

Neither more nor less likely. Genetic mutations of viruses don't punch time clocks, and are unique. The "Spanish" Flu epidemic of 1918 actually began at Fort Riley, Kansas, probably orginating in the chickens kept there to feed troops. And it was likely two strains of the same virus (H1N1), a fairly "normal" flu virus at first appearance that mutated farther into a more-deadly variant.

The variant that surfaced in the fall of 1918 was much more deadly, with mortality rates of about 8-10% among those infected, and somewhere between 3 and 5% of overall population. Nowadays the combined pneumonia/influenza death rate is about 2-3% of those infected but with much lower infection rates. The two are usually calculated together because the disease is mainly fatal among the elderly, with opportunistic post-influenza pnuemonia being the actual killer in the majority of cases.

We've had two flu pandemics since then. Asian flu in the late 1950's and Hong Kong flu in the late 1960's. The first was an H2N2 virus, and the second was an H3N2 strain that mutated out of the earlier H2N2 strain. That second strain still makes the rounds, BTW, mutating a bit to dodge the antibodies, and is the "annual flu" we see every year, one of the standard strains covered in the yearly vaccine. It kills about 40,000 people a year in the US.

The 'nearly a century' includes, as Tully, noted, already includes multiple incidences of animal->human breakthrough. No Western human megadeaths were observed.

My guess is that if this bird flu breaks through and it makes it to industrial nations, it'll have even fewer deaths than the the '60s one did. Same deal if you rereleased the 1918 flu that was recently sequenced.

the latest assessment from the AAAS

Marcus, what part of "influenza" did you miss?

The 'nearly a century' includes, as Tully, noted, already includes multiple incidences of animal->human breakthrough. No Western human megadeaths were observed.

Jon, my point is that each flu strain is unique. The short take is that we have no way of knowing what the mortality rate of a new mutation will be, and a human-to-human H5N1 would be a mutation of the bird-to-human virus. The 1918 virus started out not very much worse than most flu we see today (or not, see PDF here) but morphed into a strain that killed people literally overnight--moving too quickly for anything but immediate medical attention to affect. Obviously a nation with good healthcare infrastructure would be in better shape to deal with it, and have lower mortality rates. But the virulence and transmissibility and mortality of a not-yet-mutated strain is not very predictable.

The H5N1 form that transmits from birds to human, the "bird flu" that everyone is obsessing on right now, has an apparent mortality rate well over 50%. I say "apparent" because I'm sure many cases never see a doctor or get diagnosed. Especially milder cases. The victims get better or die and that's that, no stat assigned to the virus either way. But we have no way of knowing how nasty a mutated strain of that virus would be. It obviously has serious potential, but we're whistling in the dark in assessing probabilities.

I was looking through death records for a southern Nebraska county in 1918 last night (ya got me interested, darnit!) and the two "waves" of the 1918 flu were obvious. The first wave (in February/March) showed higher-than-normal flu mortality as compared to earlier years, nasty but certainly not devestating. Similar to previous epidemics of diptheria and such. The fall wave showed absolutely shocking numbers--there were several pages of continual "flu" as cause of death, starting at the very end of September and running through New Year's. At a guess from just the raw data, the death rate for those three months was roughly three times the usual ANNUAL death toll for that county.

The biggest "hook" I found was by noting family names and comparing them. Folks who got hit by the spring wave didn't get hit by the fall wave. Circumstantial, but still evidence that they were the same basic virus, but with much different mortality rates.

At a guess from just the raw data, the death rate for those three months was roughly three times the usual ANNUAL death toll for that county.

Should read "death toll" not "death rate." Ten times as many people or more died in those three months of flu as normally died in the county all year from ALL causes.

Egads, I've got brain lock.

The death rate for those three months was ten times the normal death rate, meaning about two and a half to three times as many people died in those three months as would normally die there all year.