Facts about Ebola

Who's at risk? The virus spreads through contact with bodily fluids, including blood, feces, urine, vomit and semen. A person also can become sick if he or she is exposed to contaminated objects, like a needle or a syringe, or by being exposed to the broken skin of an infected patient. The World Health Organization says Ebola can also be spread via "surfaces and materials" such as bedding and clothing that are contaminated with bodily fluids of infected people. People who care for Ebola patients are at high risk.

What are the symptoms? The CDC says symptoms of Ebola — which include bad headaches, vomiting, weakness and muscle pain — start to show up sometime between two to 21 days after exposure. You can't catch it by simply standing across the room from someone who has it — though scientists think it's OK to start a conversation about airborne transmission, in the interest of preparedness.

Does the Dallas case increase our risk? The case involves a man who was traveling from Liberia, a West African country that's been ravaged by Ebola. The patient is in isolation, and the hospital is trained to respond.

How do we know he hasn't already spread the virus? Officials said the patient was diagnosed here, but he wasn't ill when he flew to the United States from Liberia, where he was infected. The CDC said there was "zero risk" to people on his flight because the disease is not contagious until symptoms begin. He left Liberia Sept. 19 and arrived here the next day. He began to have symptoms on Sept. 24 and sought medical care on Sept. 26. On Sept. 28, he was hospitalized and put in isolation. He tested positive on Tuesday.