Carl Zimmer in his excellent blog, The Loom:
Here, for your viewing pleasure, is a very important part of a very special flu virus. It may look like an ordinary protein, but in fact it’s been at the center of a blazing debate about whether our increasing power to experiment on life could lead to a disaster. Not that long ago, in fact, a national security advisory board didn’t even want you to see this. So feast your eyes.
For those who are new to this story let me start back at the beginning, in 1997.
In that year, a child in Hong Kong died of the flu. Doctors shipped a sample of his blood to virus experts in Europe, but they didn’t bother taking a look at it for months. When they did, they were startled to discover that it was unlike any flu they’d seen in a human being before.
Each year, several different flu strains circulate from person to person around the world. They’re known by the initials of the proteins that cover their surface–H3N2, for example, is one common strain. The H stands for haemagglutinin, a protein that latches to a host cell so that the virus can invade. The N stands for neuraminidase, which newly produced viruses then use to hack their way out of the cell.
Birds are the source of all our flu strains. Our feathered friends are hosts to a huge variety of H and N type viruses, which typically infect their guts and cause a mild infection. From time to time, bird flu viruses have crossed the species barrier and adapted to human hosts, infecting our airways and then spreading in air droplets. Since flu spreads so fast around the world, a fair amount of the planet’s population has had some exposure–and thus some immunity–to the flu strains in circulation today. But if a new bird flu should manage to make the leap, we could face a very grim situation–a situation that some scientists worry could rival the 1918 pandemic, which killed some 50 million people.