Feeling sick? Know your bacteria vs. virus facts

What does my fever indicate?

Fever can occur in bacterial and viral infections. Think flu! But according to Dr. Peter Bornstein of HealthEast, a fever higher than 101.5 degrees is a pretty good indicator of bacterial illnesses.

Does snot color matter? Despite claims saying otherwise, the shade of your slime isn't a sign of bacterial infection. "Nasal discharge, the color of it, the amount of it — that doesn't help at all," said Dr. Frank Rhame of Abbott Northwestern Hospital.

When is it safe to go back to work or school? Bornstein recommends staying home for 24 to 48 hours after you've been diagnosed with a bacterial infection and are on antibiotics.

Viruses use proteins on their surface to invade a cell. Bacteria have fine hairs on their surface that help them attach to cells.

Antibiotics generally work on bacterial infections but not on viral infections. That's because they attack a kind of machinery in bacteria that viruses don't have.

Illnesses caused by viruses include: flu, common cold, Ebola, AIDS.

Unlike bacteria, viruses are so teeny-tiny they can't be viewed under a standard microscope.

Most respiratory viruses are spread through contact. That includes people coughing within 2 yards of each other, Rhame said. Most bacterial infections develop from bacteria that are already living inside you, he added.

Up to 15 viruses are responsible for the common cold.

Your illness may start out as a viral-only infection, but if symptoms persist, a bacterial infection may develop. "That's not because those viral infections are turning into bacterial infections," Rhame said. "It's just that the viral ones have gotten better and the ones that are left are the bacterial ones."