At least 2 million people in the U.S. each year develop an antibiotic-resistant infection, according to the Centers for Disease Control and Prevention.

Now, a new study in the journal PNAS delves into how bacteria boost their virulence.

It's a classic arms race: as hosts evolve better immune defenses, microbes develop better attacks, including swamping the body's defenses via ramped-up replication.

Geoff Hill/Auburn University

House finch with severe symptoms of conjunctivitis.

So says conventional wisdom. But a new study of house finches (Haemorhous mexicanus) before, during and after exposure to Mycoplasma gallisepticum, a microbe that can cause blindness in such birds, suggests that microbes can grow more potent without resorting to mob tactics.

Co-author Kevin McGraw of ASU said the study is especially relevant, given a recent influx of diseases that could strongly affect local wildlife.

"These types of studies are really pivotal for anticipating how organisms may be set up to respond to emerging infectious disease," he said.