Is Ebola contagious? Know more

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 diarrhoea.

Through close contact with a symptomatic person's bodily fluids, such as blood, sweat, vomit, faeces, 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.

Ebola isn't airborne. "If you sit next to someone on the bus, you're not exposed," said Dr. Tom Frieden, director of the Centres 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.

Hospitals with a suspected case call their health department or the CDC to go through a checklist to determine the person's level of risk. Among the questions are whether the person reports a risky contact with a known Ebola patient, how sick they are and whether an alternative diagnosis is more likely. Most initially suspicious cases in the U.S. haven't met the criteria for testing.

The CDC says bleach and other hospital disinfectants kill Ebola. Dried virus on surfaces survives only for several hours.