North America's three biggest measles outbreaks continue to balloon, with more than 2,500 known cases; three people have died ...

Guatemala and Mexico at the southern end of its journey. The way nature ignores borders poses serious problems for conserving migratory animals — and for environmental problems in general.

They're the same roads used by thousands of families and commercial truckers who cross into Mexico and back each day. “Diseases know no borders ... traveling country to country,” said ...