It’s been a rough flu season this winter in the United States and Europe, but it could be worse. A lot worse. The flu viruses that are making us sick go by names like H1N1 and H3N2, referring to the kinds of proteins that stud their surface. There’s another sort of flu lurking in other parts of the world, like Egypt, India, and Cambodia, known as H5N1. Since 2003, 615 people have come down with H5N1, and, as of Feburary 1, 364 of them had died. In January alone, 5 people in Cambodia were diagnosed with H5N1. Four of them died.
There’s a lot of debate about precisely how bad H5N1 is. It’s possible that a lot of people are getting sick with H5N1 without making it onto the official records. They’re crawling off to bed for a week, recuperating, and then getting on with their lives. So the 59 percent death rate you get from the official numbers (what’s known as the case-fatality rate) may be a serious overestimate. Still, even if the true rate was only half as high, H5N1 would not be a virus you’d want to cross paths with. The most famous flu outbreak of all, the so-called Spanish flu of 1918, is estimated to have killed 50 to 100 million people worldwide. But it infected billions, with a death rate of roughly 2 percent. If H5N1 could somehow take off and become a global pandemic, it would become an unparalleled catastrophe even if its official 59 percent case-fatality rate was chopped down by a factor of ten.