The rapid spread of Zika virus has escalated anxieties and raised many questions about how the virus is transmitted and what kind of threat it may pose.
The virus has been linked to serious birth defects in Brazil, where as many as 1.5 million people have been infected and about 4,000 babies have been born with a condition called microcephaly, an abnormally small head which may result in mental retardation. Some adult patients have developed Guillain-Barré syndrome, a condition that may leave them paralyzed for days or weeks.
CBS News chief medical correspondent Dr. Jon LaPook recently traveled to Recife, Brazil, the epicenter of the Zika outbreak, to get a firsthand picture. While there, he held a Facebook Q&A session to help answer questions about the virus.
Q: How concerned should we be about people returning from Carnival in Rio?
A: This gets to the issue of how is the virus transmitted. The vast majority of cases are transmitted by a mosquito, the Aedes aegypti.
The virus is inside the mosquito and the mosquito bites somebody and then transmits the virus to them. If a person gets infected in Brazil, and that person then travels to the U.S., the virus is in the bloodstream for about a week, the CDC says. When a person comes to the United States, they could still have the virus in their bloodstream for seven to 11 days.
Also, an uninfected mosquito [in the U.S.] could bite an infected person and pick up the Zika virus from the infected person. That [newly] infected mosquito could then turn around and bite an uninfected person and then you would have local transmission of Zika by a mosquito that is in the United States. That hasn't been shown to happen yet.
Q: If it spreads to the U.S., which areas are more at risk?
A: Most experts say it's likely Zika will come to the U.S. at first in South Florida, the Gulf Coast and Texas. But we're protected in the U.S. because there's a true winter. We have [window] screens and air conditioning and the conditions here are in general better than in Brazil.
Q: What are some other ways Zika may spread?
A: There was a case of sexually transmitted Zika reported in the U.S., so that is a route people are now considering. Experts are also looking at the possibility that it could potentially hit the blood supply from people who feel well [and don't know they have Zika infection] and donate blood.
There haven't been any cases of sexually transmitted Zika documented in Brazil, but public health officials there are looking into this more.
Q: Once you have Zika do you always have it? And will any babies you have be at risk for small heads [microcephaly]?
A: This is a theme we've been asked a lot about. It goes to the question of how long the active virus is in your bloodstream. It's reasonable to think - and I confirmed this with Dr. Anthony Fauci, head of infectious diseases for the National Institutes of Health - that once you develop immunity and get antibodies to it (after the acute infection), and once that immunity is in place and you're feeling well, that it shouldn't be a risk years later to get pregnant, or to the fetus. That said, a lot of information is not known yet.
Q: If it comes to America, what can we do?
A: I don't discount the fears, but you don't want to panic. Just know the facts. For the most part, it's transmitted by mosquitoes. The experts think it can spread here but it shouldn't be the widespread kind of outbreak that you're seeing in Brazil, for example, where there are about 1.5 million cases and maybe even growing.
You can use air conditioning, bug repellant, and screens. And of course, if somebody is returning from one of these countries and could potentially be infected, after the report of possible sexual transmission, I think it's reasonable to stay away from that person until they are declared absolutely, positively cleared of any kind of active viral infection when it comes to having any kind of sexual relations.
Q: Is there any information about a vaccine?
A: Yes, Dr. Anthony Fauci from the NIH said they expect a phase I trial to start by the end of this year. But it's going to take several years - possibly two to five years - before a vaccine is widely available.
Q: Is it just dangerous for pregnant women, or should we all be concerned?
A: There has been a condition called Guillain-Barré syndrome, a neurological syndrome, which can cause paralysis of the lower extremities and other neurological problems that can happen with the Zika virus.
Right now Zika has been described as a very mild type of illness: aches, pains, fever, rash, conjunctivitis (red eye). It should be over within a week or so for most people.
Eighty percent of people have no symptoms, and that's what makes this so hard because if you've been in one of these countries and come back, you want to know if you've been infected.
Q: Is there a test to tell you if you've been infected?
A: A test called a PCR test can tell if you have active virus in your bloodstream. But the test to see if you have antibodies, to see if you were infected in the past - that's not as accurate. And it's not as widely available and can give a false positive if you were previously infected with dengue fever or yellow fever, or if you have had a yellow fever vaccine.
Q: Is there any evidence that the Zika virus is carried in mosquitoes in the U.S. yet?
A: Not yet. I think there's a near certainty that it will be found eventually in mosquitoes in the United States. But that is not the end of the world. We have a lot of work to do. We have to figure out innovative ways of attacking it, such as these genetically modified male mosquitoes that pass on a gene to the larvae that makes them die before they come to adulthood. People are making sure mosquito breeding grounds are eradicated. That's what's happening in Brazil. Soldiers from the government were going house to house to identify places where mosquitoes might possibly be growing. They're also educating people.
Q: Is there a timeframe during pregnancy that is higher risk?
A: We're not sure, exactly. But in general, there's a lot of [fetal] growth that's happening in the first trimester, especially neurologically. So one would think logically that that could be a time when it could be passed.
Q: Are babies at risk for developmental issues if they become infected?
A: Yes, based on other experience with microcephaly. Maybe there are other developmental problems that are not as obvious. So anybody who has any evidence of Zika exposure in utero - if the mother had evidence of it - you're going to want to follow these people very closely.
Q: Can it be passed in breast milk?
A: I don't know the answer to that. I haven't seen anything about that, but again that's something people are going to look at.
Q: Can it spread through saliva?
A: Scientists have detected evidence that the virus can be found in saliva samples. What does that mean? Can you actually get it from kissing somebody, with saliva? From what we know, and Dr. Anthony Fauci, who's the head of infectious diseases for the NIH told me, just because you have virus in the saliva doesn't mean that you can give it to somebody that way. I think that's a very important thing.
Dr. LaPook wrapped up his Q&A by talking about the emotional toll the illness has taken on families in Brazil. He said he met a couple whose baby has microcephaly, who loved their baby, but were very concerned about the social stigma the child may face throughout life. "Seeing babies with microcephaly was very emotional," he said. "When you look in their eyes, and when you look in the eyes of the baby, it takes your breath away."