Posted: June 6, 2007
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The four faces of bird flu

CIDRAP Business Source Weekly Briefing
and the CIDRAP Business Source website, January 24, 2007
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Bird flu is four problems, not one. Keeping them straight is a prerequisite to sensible risk communication – and sensible preparedness.

Vocabulary lessons are a pain. But sloppy language use has encouraged sloppy thinking, greatly compounding our preparedness problems. Millions of people think flu pandemics come from birds. Millions think Asia already has a pandemic. Millions think when the pandemic gets here the only people it will endanger are those who get the flu. These mistakes are grounded in confusion about the four faces of bird flu.

So grit your teeth for a crucial vocabulary primer.

1. The ongoing epizootic

A widespread infectious disease outbreak in a nonhuman species is called an epizootic.

An epizootic of the influenza strain called H5N1 is currently wreaking havoc among birds in parts of Asia and Africa. This strain of H5N1 is incredibly infectious and incredibly deadly to domestic poultry. It is the worst bird flu in recorded history. Even if it never becomes a serious human health problem, it will remain a big deal for farmers and veterinarians.

Many experts think H5N1 is already widespread enough to be considered a panzootic (worldwide outbreak) instead of an epizootic; others think that’s premature, since it hasn’t been found yet in the western hemisphere.

For decades, animal outbreaks have routinely been called epidemics and pandemics instead of epizootics and panzootics by professionals who know better. It’s probably too late to cure them of this bad habit. But readers of this newsletter shouldn’t follow them into it. Distinguish the current animal epizootic from the possible future human pandemic. (The experts defend their longstanding historical misuse of the technical vocabulary – all the while ridiculing the media and the public for getting confused. Wouldn’t it be neat if businesspeople were to start using the terminology correctly?)

2. The occasional zoonotic infection

From time to time a disease that’s common in animals passes to an unlucky human or two. That’s called a zoonotic infection.

As of Jan 24, H5N1 has infected 269 people that we know about, out of millions of people exposed to infected poultry. H5N1 passes easily from bird to bird. But so far it passes from bird to human only with great difficulty – and from human to human with greater difficulty still.

What’s scary is this: While very few people have become infected with H5N1, a huge percentage of that tiny number – roughly 60% – have died. That compares to a US case fatality rate of about 2-1/2% for the infamous 1918 flu pandemic, and far below 1% for the typical seasonal flu.

A 60% case fatality rate is terrifying. But H5N1 is still a minor public health problem. Even poultry farmers whose flocks contract the disease face a surprisingly small risk to their health – so small that they rightly smell a rat when authorities say they need to kill their birds to keep themselves healthy (rather than to keep the disease from spreading to nearby flocks). The zoonotic risk faced by chicken consumers and other non-farmers is immeasurably small.

For zoonotic infections to become a major problem, the virus would have to mutate in a way that enabled it to pass easily from birds to humans. Nobody talks much about that possibility. Most experts are guessing that it’s probably less likely than the possibility they talk about incessantly: that H5N1 may mutate so it passes easily from humans to humans.

3. The mild pandemic

If H5N1 ever “learns” efficient human-to-human transmission, we will have a pandemic. By then H5N1 probably won’t be bird flu anymore. It will have mutated (or reassorted) into a human flu – a new human flu to which we have no natural resistance and for which we have (at the start) no vaccine. At that point, unless zoonotic infections become common for the first time in influenza history, birds will cease to be an issue. We’ll be worrying about catching the disease from each other. The pandemic risk in places where the birds are healthy will be exactly the same as the risk in places where they’re infected.

Of the four “faces” of bird flu, in other words, two of them aren’t bird flu all; they are possible pandemic descendents. Phrases like “bird flu pandemic” are intrinsically confusing. Such phrases confuse the two bird flu problems we have now (bird-to-bird and bird-to-human) with the two pandemic, human-to-human problems we’re worried about.

Why two pandemic problems? Because not all pandemics are the same.

Do you have vivid memories of the pandemics of 1957 (H2N2) and 1968 (H3N2)? Neither do I. They were serious enough to kill significantly more people than the typical flu season kills. They were serious enough to lead to some hospital surge capacity problems and even some business absenteeism problems. But unless you were paying close attention or happened to know someone who became sick, they were easy to miss.

Note: Some experts argue that today’s just-in-time supply chains are so fragile that even a mild pandemic could have severe impacts. This effect might be exacerbated by the fact that the next pandemic will be the first pandemic people were watching for. If supply chains are clamped shut in anticipation of a devastating medical emergency, the result could be a devastating infrastructure emergency even if the pandemic itself is mild.

If H5N1 causes a pandemic like those two, it will be something of an anticlimax. Companies worried enough about pandemic preparedness to subscribe to this newsletter will presumably cope better with a mild pandemic than non-subscribers. But non-subscribers will get through it okay, too. And both will wonder a bit what all the fuss was about. (See Note at right.)

4. The severe pandemic

By contrast, the 1918 pandemic (H1N1) killed more people than World War I. It was the mother of all flu pandemics. If H5N1 causes a pandemic like 1918’s, nobody is going to think it anticlimactic.

Nor is 1918 the worst-case scenario. What if H5N1 acquires efficient human-to-human transmission without becoming less fatal in the process? Imagine a disease that’s as contagious as a bad flu season (infecting, say, 30% of the population) and as deadly as H5N1 is today (killing 60% of those it infects). It would be an unprecedented human health catastrophe. Since a flu pandemic that bad has never happened before, most experts figure it probably won’t happen this time. But H5N1 has already broken a lot of influenza records. And things that have never happened before happen all the time.

Medically, two factors determine the severity of a pandemic: what percentage of the population gets sick, and what percentage of those who get sick die. But there’s a third factor that’s at least as important as those two: how much the pandemic disrupts society’s infrastructure. Does the power go off? Does the water treatment plant run out of chlorine? Do the supermarkets run out of food? Are diabetes patients unable to replenish their supplies of insulin and syringes? Are there riots and looting? Does your company stop performing even its most essential functions?

What sort of pandemic a society prepares for depends on who’s in charge of preparing. To most departments of health, pandemic preparedness is about social distancing, about quarantine and hygiene strategies, and about having enough medicine, ventilators, and nurses to cope with the influx of flu patients. In other words, health departments are preparing mostly for a mild pandemic. Departments of emergency management, on the other hand, are thinking about keeping the power going and the water potable. They’re worried about infrastructure resilience and social stability. They’re preparing for a severe pandemic.

Smart companies are preparing for both – and being clear about the difference.

Copyright © 2007 Regents of the University of Minnesota. Originally published on
the CIDRAP Business Source website, January 24, 2007. Reproduced with permission.

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Contact information page:    Peter M. Sandman

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