We asked you to submit your questions about the Ebola virus on-air and online and we said we would get them answered by an expert from the Centers for Disease Control and Prevention.

GPB News reporter Jeanne Bonner took your questions to Dr. Beth Bell of the CDC. Here are Bell's answers.

GPB News Jeanne Bonner: Our first question came from Marlon Chapman of Lawrenceville, who asks about the origin of the Ebola virus.

Dr. Beth Bell: The Ebola virus was first detected about 40 years ago in the part of Africa that is currently Democratic Republic of Congo. We don't know for sure but we think likely the Ebola virus emerged as an infection of humans transmitted from some sort of animal. We think probably the reservoir for Ebola is probably bats but we really don't know whether the first human infections occurred because of direct exposure to bats or perhaps exposure to other animals like primates that had been infected from bats.

GPB News Jeanne Bonner: Another listener wants to know if someone can be a carrier for Ebola and unknowingly infect someone else.

Dr. Beth Bell: I think usually when people say 'carrier', they are thinking about chronic infection. And the answer is to that question is no. There is no chronic infection with Ebola. A person develops symptoms, they are contagious at that time and when they resolve their symptoms and they get over Ebola, they no longer have any virus in their blood and they are not contagious.

GPB News Jeanne Bonner: (This question) comes from Tina who wants to know if the CDC will be honest if the outbreak becomes even more serious.

Dr. Beth Bell:We at (the) CDC are a science–based organization. We base everything we do on the best information available and we stake our name on making evidence–based decisions and telling the truth. I think that people can be comfortable that we will be transparent and we will provide people with the information that we have as soon as we have it.

GPB News Jeanne Bonner: Amy and (a comment from our News Muse blog who goes by the handle Concerned Mom posed a similar question). They want to know if someone who doesn’t have Ebola symptoms but later develops the virus can spread it by sneezing on a surface such as a table that someone else then touches.

Dr. Beth Bell: People are not contagious with Ebola until they develop symptoms. People don’t have to be concerned about people who have Ebola but don’t know it and giving it to someone else because that doesn’t happen. We cannot detect Ebola in the blood of people who turn out later to be infected once they develop symptoms. And indeed even very early on after people develop symptoms, there is a very small amount of Ebola in the blood. Very important point: not contagious if not symptoms.

GPB News Jeanne Bonner: Another question involved the likelihood that the virus could mutate and become easier to catch.

Dr. Beth Bell: In science and public health, you never say never. But it is really our responsibility to focus on the most urgent threats while keeping our eye on these less likely things. We really think it is highly, highly unlikely that the Ebola virus would mutate in such a way that it would suddenly develop a new way to be spread.

GPB News Jeanne Bonner: What about screening passengers from three West African nations, which begins Thursday at Hartsfield–Jackson International Airport.

Dr. Beth Bell:The most important part of this is stopping the outbreak in West Africa. That is (the) best way to protect Americans is for us to continue to work as hard as we are to stop the outbreak in West Africa. We have a number of other things that we are doing. People should be aware there is exit screening happening in each of the three countries where the outbreak is occurring, Liberia, Guinea, and Sierra Leone. That means there are trained workers at the airport that take everyone's temperature and asking a series of questions, and anyone who answers yes to the questions or has a temperature is not allowed to board.