All Across the World, Swans Are Dying

Noted today in Slate:

Avian influenza continued its advance across Europe this week: On Monday, health officials in Poland reported evidence of the virus in a pair of dead swans. On Tuesday the Bulgarian government pledged to sanitize the area where four infected swans had been discovered. The highly pathogenic H5N1 strain has also turned up in dead swans in Austria, Bosnia, Croatia, Germany, Greece, Hungary, Iran, Italy, Serbia, and Slovenia. Why do we keep finding bird flu in swans?

For the answer, read on.