Just when you thought it was safe to go back to the hen house, bird flu is on the rise again. Earlier this century, avian flu led to the worldwide culling of more than 400 million poultry. When the virus jumped from birds to humans, more than 300 people died.

Although control practices have cleared the virus from most countries, it still remains a problem in a few, mostly in Asia and the Middle East. And this fatal flu may be on the rise again as wild birds carry the virus across borders to infect domestic flocks in new areas like Eastern Europe. Worse yet, a mutant strain has emerged that sidesteps the protection offered by current vaccines.

The best hope for halting this winged plague in mid-flight is heightened surveillance and redoubled control measures that reach across national borders, just like the birds do.