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Swine Flu Pandemic FAQ

What the swine flu pandemic means to you.

What does the WHO pandemic alert mean?

The World Health Organization has declared the 2009 H1N1 swine flu to be a pandemic.

That does NOT mean that swine flu is more dangerous than it was before. The declaration means only that the WHO officially recognizes that swine flu is spreading globally -- and that countries that have not yet put their flu-pandemic plans into action should do so now.

Swine flu already has been spreading in the U.S., so the WHO declaration makes very little difference. U.S. health officials already have been working furiously to prepare for the fall 2009-2010 flu season.

Why has WHO declared a pandemic now?

WHO's technical criteria for declaring a pandemic is that the infection must be spreading locally in at least two distinct regions of the world. That actually went on for some time before the official declaration.. But the WHO was worried that governments might overreact to a pandemic declaration.

They had good reason to think so. Early in the pandemic, some countries stopped importing pork and even slaughtered local pig herds -- even though the so-called swine flu is spread from person to person and cannot be spread by eating pork. And other nations established unreasonable travel restrictions or unnecessarily quarantined healthy people from countries where the flu was spreading.

These unnecessary actions had serious economic and social impacts. And since most public health experts feared that the next flu pandemic would be the vastly more deadly H5N1 bird flu, most pandemic preparedness plans contained steps far more drastic than steps needed to fight swine flu, which is only moderate in severity.

The six-stage WHO pandemic alert system does not take disease severity into account; it's based on the geographic spread of a virus.

The CDC does have a pandemic severity scale, which has five categories. The scale is based on the percentage of infected people who die -- the case-fatality ratio.

It's too soon to know the case-fatality ratio for H1N1 swine flu. But the CDC's best estimate so far is that it is 0.1%. That puts it on the borderline between Category 1 (the lowest category) and Category 2. The 1918 swine flu was a Category 5 pandemic, with a case-fatality rate of over 2%.

Even a Category 1 pandemic is serious. The CDC estimates that a pandemic with a 0.1% case-fatality ratio would result in some 90,000 U.S. deaths if no vaccine becomes available.

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