Pathogen

A pervasive fungus, passed along by pigeon droppings, can kill HIV patients by using a Trojan Horse strategy to invade their brains.

The good news: Antibiotics didn't create antibiotic-resistant bacteria. The bad news: Antibiotic-resistant bacteria is everywhere.

Human disease is littered with examples of fractious, sometimes furious rows over what emerging pathogens are called.

You've eaten boogers before—admit it. You might even do it now. Either way, one biochemist thinks you're onto something.