Ebola: How does the virus spread?

This undated photo made available by the Antwerp Institute of Tropical Medicine in Antwerp, Belgium, shows the Ebola virus viewed through an electron microscope.

While health officials are casting a wide net to find people who may have been around the Ebola patient now hospitalized in Dallas, they're also stressing that it takes close contact to really be at risk.

WHEN IS EBOLA CONTAGIOUS?

Only when someone is showing symptoms, which can start with vague symptoms including a fever, flu-like body aches and abdominal pain, and then vomiting and diarrhea.

HOW DOES EBOLA SPREAD?

Through close contact with a symptomatic person's bodily fluids, such as blood, sweat, vomit, feces, urine, saliva or semen. Those fluids must have an entry point, like a cut or scrape or someone touching the nose, mouth or eyes with contaminated hands, or being splashed. That's why health care workers wear protective gloves and other equipment.

WHAT ABOUT MORE CASUAL CONTACT?

Ebola isn't airborne. "If you sit next to someone on the bus, you're not exposed," said Dr. Tom Frieden, director of the Centers for Disease Control and Prevention.

"This is not like flu. It's not like measles, not like the common cold. It's not as spreadable, it's not as infectious as those conditions," he added.

HOW IS IT CLEANED UP?

The CDC says bleach and other hospital disinfectants kill it.