Wednesday, March 22, 2006

H5N1 and Dissacharides

CNN and the BBC recently reported results from this Nature paper on why the Avian Flu Virus (H5N1) does not readily spread between humans. Viruses can recognize certain dissacharides on the surfaces of cells. Dissacharides (think 'double-sugars') can be attached in a number of different ways. It turns out that human flu viruses bind preferentially to a dissacharide composed of sialic acid connected to galactose via a α-2,3 linkage. Avian flu viruses recognize an almost identical dissacharide: sialic acid connected to galactose via a α-2,6 linkage.

In humans it turns out that the α-2,6 liked dissacharide is mostly found in the bottom of the lungs. So if you're unlucky enough to get the H5N1 virus all the way down to the bottom of your lung, you're sunk. Fortunately for the rest of us, it's pretty unlikely (since it way at the bottom) that you'll sneeze or cough any virus up at your neighbors.

So right now it looks like the fact that this virus prefers the bottom of our lungs is a major part of why this virus isn't sweeping across the planet (yet). So avoid playing with severed chicken heads and you'll be okay.

This story was also covered by Chemical & Engineering News.