Is H5N1 really that deadly?
Latest thoughts from Dr. Michael Osterholm - Part II

Latest thoughts from Dr. Michael Osterholm - Part I

Dr. Michael Osterholm has just given a Minneapolis newspaper his current assessment of the H5N1 threat. He says H5N1 "continues to march" and genetically is "kissing cousins" with the 1918 pandemic flu virus. He believes the antiviral drug Tamiflu could work in treating an H5N1 human flu - but might need to be administered sooner and in higher dosage than for seasonal flu because of the severity and rapid onset of H5N1 infections. He sees pitfalls in the world's limited vaccine manufacturing capacity, the just-in-time production of many medicines, and the inadequate "surge capacity" in hospitals.

For his detailed observations, read on.

If you're not familiar with Dr. Osterholm, he's director of the Center for Infectious Disease Research and Policy (CIDRAP) and professor in the School of Public Health at the University of Minnesota. He is also a member of the Institute of Medicine of the National Academy of Sciences. Previously, Dr. Osterholm spent 24 years at the Minnesota Department of Health, including 15 years as state epidemiologist. He is a frequent consultant to the World Health Organization (WHO), the National Institutes of Health (NIH), the Food and Drug Administration (FDA), the Department of Defense, and the U.S. Centers for Disease Control and Prevention (CDC). He is a fellow of the American College of Epidemiology and the Infectious Diseases Society of America.

In other words, he is qualified in his field. He also has been one of the leading proponents of pandemic preparation.

In a local newspaper interview in Minneapolis on March 22, 2006, Dr. Osterholm noted that H5N1 avian influenza remains a bird virus, not a human virus. And he thinks the arrival of infected birds in North America, perhaps sometime this year, is not likely to result in many human infections, because most domestic poultry here is raised in settings that prevent contact with wild birds.

The question - the worry - is whether and when the H5N1 virus mutates to a form that's easily passed from human to human. If that happens anywhere in the world, says Osterholm, the resulting pandemic would spread worldwide in short order. Along with it would come overloaded hospitals and disrupted economic supply chains.

And there will be other flu pandemics. But, "Will H5N1 be the [next] pandemic strain, and will it occur in the next six to twelve months? The answer is, we don't know," Dr. Osterholm says. If it does "go pandemic," will it remain as deadly as it has been thusfar - killing over half of the people it infects? Again, Dr. Osterholm says we don't know.

Below are some of Dr. Osterholm's comments on the nature of the H5N1 virus, the possibility of an H5N1 flu pandemic, and the ramifications if such were to occur.


On the uncertainty of whether H5N1 will cause a pandemic:

So this thing just continues to march. Changes are occurring in it all the time. [Human-to-human transmission] could happen tonight. Or it may never happen. But I don't know what will keep it from happening.


On similarities between H5N1 and the H1N1 virus which caused the 1918-19 Spanish Flu pandemic:

And what is very, very troubling to us is that it's mutating in very similar fashion to the way the 1918 virus did. We went back with the 1918 virus and found all eight genes of that virus in tissue samples... And by studying that, they could determine how it actually mutated and jumped directly to humans from birds. It didn't go through other species as the 1957 and 1968 viruses did, where a bird and a human virus got together, most likely in a pig, [and] combined to make a third, dumbed-down virus that caused mild pandemics.

One of the problems we've had is, if you look at the 1918 virus and this one, they're in essence kissing cousins. Genetically, these things look very similar.

If you put 1918 H1N1 into animal models at very, very low doses, it basically kills all of them in 24 hours. The lab science people had never seen that. At 16 to 24 hours, that virus was different from anything they'd ever seen in killing these animals. The only virus that was similar was H5N1, and it was fatal at much lower doses. H5N1 is the most powerful influenza virus we've seen in modern human history.


On the "cytokine storm" phenomenon which made the 1918 virus - and thusfar H5N1 - so fatal. (A cytokine storm occurs when the immune system overreacts and damages the body, causing failure of multiple organ systems. [Glossary]):

This virus is quite different from what we see with the standard annual flu, and what we saw in 1957 and 1968, because of the cytokine storm it causes. In 1918, the vast majority of the people who died were healthy young people, 20 to 40 years of age. And that was in large part because they had the strongest immune systems.

And that's what we're trying to understand at this point, in terms of how to best prevent this [immune reaction]. And right now it doesn't look like there's much you can do.

What makes [the 1918 virus and H5N1] so similar is that they both cause this cytokine storm phenomenon.


On whether a pandemic-causing H5N1 would maintain its current virulence (ability to cause severe disease):

That's a really critical question. We can only anticipate that this will attenuate. Meaning that once it starts spreading in humans, it will lose some of its punch in order to better adapt to humans. That's traditional with virtually all agents you see like this.

[But,] we don't know how much. We talk about a worst-case scenario in terms of what happened in 1918, when roughly 2.5 percent of the world's population died. Of those who contracted it, roughly 5 to 6 percent of populations died.

The mortality rate so far for this virus is around 55 percent. So this virus would have to attenuate a lot to get down to that level.

This [virus] is not causing a lot of asymptomatic infections right now. ... That means we're not artificially inflating the mortality rate by missing a lot of infections. I'm actually pretty confident that the real mortality is almost that high [55%].

So for that number to drop all the way down to a couple percent is a pretty big drop. Which says to me that when people talk about 1918 as a worst-case scenario, well, maybe that isn't the worst-case scenario. That's hard for people to hear, because then they think you're really trying to scare the hell out of people. But you know what? It's just the data.

If this virus were to ultimately go human-to-human, none of us know what the human mortality would be.

Tomorrow, more comments from Dr. Osterholm on:

  • His belief that a "fire blanket" response would not contain the initial pandemic outbreak(s).

  • The prospects of using the antiviral Tamiflu to treat H5N1 infections.

  • The consequences of a worldwide vaccine manufacturing bottleneck.

  • The possibly disrupted flow of imported products and supplies.

  • The lack of "surge capacity" in hospitals and elsewhere.

Prepare. Early.