Taking the measure of the swine flu pandemic

by revere, cross-posted from Effect Measure

Crafting a message on swine flu is not easy, and it's easy to make missteps. I think CDC has gotten it pretty much right over the last two months, but not everyone has. We've written here since the beginning (some examples here and here) that describing any flu outbreak as "mild" is inapt. Flu always has the potential to be a serious disease and kill people, even in flu seasons termed "mild" by comparing them to flu seasons that are "bad." Even with virulent flu viruses many people have minimal illness -- in comparison to those who don't. But flu, even in its most common form of a self-limiting illness with complete recovery, is often a miserable affair during its acute phase and it can leave a person debilitated for extended periods afterwards. For some there's nothing mild or self-limiting about it. A bout with the flu becomes a mortal threat that can make good on its fatal potential.

Now the frequent use of "mild" by public officials to characterize swine flu is causing concern:

The heavy reliance on the word "mild " could be creating a false impression of what is actually going on and what the world may face in coming months, some experts worry.Peter Sandman, a risk communications guru from Princeton, N.J., suggests if authorities are trying to ensure people don't panic about the new H1N1 outbreak, they are concerned about the wrong thing.

"In North America, swine flu panic is much rarer than swine flu deaths," Sandman says.

"The problem isn't panic or even excessive anxiety. The problem is complacency, both about what's going to happen and about what might happen." (Helen Branswell, Canadian Press)

Officials tend to minimize the seriousness of these things for two reasons, one conscious, the other unconscious. The conscious one is to allay public anxiety, anxiety which can have significant public health consequences if it causes emergency rooms to clog up with people worried they might have something much worse than how they feel. The unconscious reason is that public officials don't want it to be bad, because they know what that would mean. Their job would become orders of magnitude more difficult and if they were wrong about the seriousness they'd be accused of overreacting. It's a fine line. Here's how CDC's Dr. Anne Schuchat walked it last week during a press briefing:

In the U.S., our antiviral recommendations are based on the observation that the vast majority of people who get this new virus have illness that is mild and clears on its own or they have illness that gets better. It's not mild, you can be quite miserable in bed for a few days, but it doesn't lead to complications in most people. On the other hand, pregnant women, people with underlying medical conditions like asthma and diabetes, can have a much worse outcome. They can get pneumonia. They can have severe hospitalizations and, of course, some of them are dying. (CDC transcript)

Not perfect, but on the whole, accurate. The only thing missing is to be clearer that a significant proportion of people who become seriously ill are otherwise healthy and relatively young for having a bad flu outcome. Over the years I have become aware that most people have no idea what it's like to have a solid case of influenza. They still think of it as like a "bad cold," even though public health authorities have tried to dispel this myth. Unfortunately the message that swine flu is a mild disease has reinforced this misconception.

We have still to get a good handle on how nasty this virus is, even in flu terms. WHO's Keiji Fukuda has termed the severity of this pandemic "moderate," similar to the 1957 pandemic. In the northern hemisphere the virus continues to circulate robustly, even though it is summer. Reports from the southern hemisphere, which is just entering its traditional flu season now, suggest it is building up quite a head of steam there. Whatever its virulence (which is uncertain at this point), it is behaving epidemiologically like a pandemic strain, which means it is infecting and making seriously ill younger people (and in fact seems to be sparing the elderly) and because of the lack of population immunity it may be capable of infecting many more people than the usual seasonal flu. If the virulence remains the same, a proportionate increase in infected people will result in a proportionate increase in seriously ill people. But virulence may also change. Even moving the average virulence a small amount can cause extremely large proportionate changes in the serious cases. If you double the demand for pediatric ventilators you can have a very big medical care problem, just to take one example. How fast cases accrue will also be critical. If it happens fast it has a very different effect than if it is spread out over many months.

Public health authorities up north are counting on having some advance warning on how bad things can get by seeing what is going on in the southern hemisphere. But the virus may not give anyone that luxury. Countries like Australia, Argentina and Chile are already getting hammered and the virus seems to be increasing in places in the north at the same time. In other words, we have yet to take the measure of this virus.

Whatever that measure turns out to be, I feel pretty confident that "mild" won't be a word to describe it.

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