The Pandemic of 2009

The World Health Organization has officially declared a pandemic as a result of the rapid worldwide spread of Influenza A (H1N1), formerly known as swine flu. But that does NOT mean that a lot of people will die. By definition, a pandemic is simply a widespread outbreak of a new human flu virus that spreads rapidly from human to human, causing human illness.

Some flu pandemics cause only mild symptoms and few deaths – others can be quite deadly. The best-known pandemics of the last century were the deadly Spanish flu of 1918 (20-40 million deaths), and the milder Asian flu of 1957 (1-4 million deaths) and Hong Kong flu of 1968 (also 1-4 million deaths). In contrast, the milder seasonal flu that many of us get nearly every year kills “only” about a quarter of a million people each year.

Pandemics are of concern to public health officials (and the public!) because the virus spreads so quickly and because the consequences of the spread cannot always be predicted in advance. Fortunately, it now appears that this pandemic will be no more deadly than the typical seasonal flu that many of us get nearly every year. Most people who become infected with Influenza A (H1N1) are recovering without the need for medical care. But it could have been otherwise, and that’s why health officials were so concerned at first and why they are still watching it closely.

The other flu we worry about is avian flu (see Human Biology 5th ed., pp. 540-541). Avian flu is VERY deadly in the few cases in which it has been caught from birds, but human-to-human transmission is still exceedingly rare.