All Your Zika Questions Answered

— -- As the Zika virus spreads, many people are concerned and unsure about what the virus does and where it is transmitted. ABC News' Chief Health and Medical Editor Dr. Richard Besser compiled a list of the most common questions and his answers.

The number of countries with proven Zika virus transmission is growing. That is because according to the Pan American Health Association, the mosquito that transmits the virus is found in every country in the Americas except for Chile and Canada. That means the potential for disease transmission exists. If a country has transmission of dengue virus or Chikungunya virus, it likely will have Zika virus transmission since they are spread by the same mosquito. The CDC keeps a list of countries for which they have a travel advisory for pregnant women and some trying to get pregnant. However, the list will be continually changing and it's possible that some countries not on the list may simply not be looking as hard for Zika.

For most people a Zika virus infection causes no symptoms at all. For those who develop symptoms, the illness is usually mild. However, there is growing evidence of a link between Zika virus infection during pregnancy and severe brain damage in the developing fetus. For that reason women who are pregnant or trying to get pregnant should avoid travel to affected countries if at all possible.

The primary means of Zika virus transmission is by mosquito. To transmit the virus, a mosquito must bite a person who is infected with Zika virus and then bite another person. The virus is transmitted by the mosquito's saliva. If you can avoid getting bitten by mosquitoes, you can prevent infections.

There is some evidence that in rare occasions Zika virus may be sexually transmitted, however, some scientists feel this needs additional confirmation. As an added precaution, health officials in the United Kingdom recommend that men who are returning from Zika-affected countries use condoms during sexual intercourse for days if their partner is pregnant or trying to conceive.

The virus is not transmitted by other forms of close contact.

Eighty percent of people will have no symptoms. Those who do get ill, many have a mild illness with fever, headache, rash, red eyes, and joint pain. There is some indication that Zika virus infection increases the risk of having a rare neurological condition called Guillain-Barré syndrome, a form of paralysis that is usually reversible. There are studies under way to look at this possible connection.

There is much we don't know about Zika virus since it has not been well studied and has been felt to be a mild illness. According to experts at the CDC and NIH, similar viruses do not linger in the body after a person has recovered from the infection. After a couple weeks virus is undetectable in the blood. Once the virus is gone, there should be no effect on future pregnancies.

There have been no cases of disease transmission in the United States. The mosquito that transmits Zika is found in many parts of the country so it is possible that there will be limited transmission once winter is over and mosquitoes get more active. Experts do not believe there will be widespread outbreaks in the United States for several reasons. We have not experienced widespread outbreaks of dengue fever and chikungunya, other diseases transmitted by the mosquito that spreads Zika. This may be because this mosquito, Aedes aegypti, tends to be a daytime, indoor biter. It breeds in water in and around the home. Since most homes in America have windows and screens, there are fewer opportunities to get bit and spread the infection.

There are many unanswered questions. It is not known whether there is a time during pregnancy when the virus no longer poses a risk. It is not known if there is a period that is riskiest for getting the infection. There are currently studies under way and being planned to answer these very important questions.

Thankfully, Zika is very different than malaria. There is no evidence that Zika virus stays in your body after you have recovered from infection.