Zika Virus Outbreak: Inside the Hot Zone

Following the outbreak from Brazil where families are dealing with devastating effects to how it traveled to the United States.
7:46 | 02/03/16

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Transcript for Zika Virus Outbreak: Inside the Hot Zone
The mysterious disease causing international anxiety. We're in Brazil, ground zero of the zika outbreak, with disease detectives trying to stop the contagion from spreading. The world health organization declaring a global health emergency. Here in the U.S. With at least 50 cases now confirmed there is mounting concern. Here's ABC's chief medical editor Dr. Richard Besser. Reporter: 3-month-old Anna Beatrice, who's like any Normal baby -- but Anna was born with microcephaly, an extremely small head, due to abnormal brain development. A devastating neurological condition that doctors suspect is linked to zika virus infection during pregnancy. In Brazil the Barbosa family is one of thousands of families dealing with the virus. Roughly 150 cases of microcephaly occurred in Brazil in 2014. Last year, there were more than 4,000. Anna's mother Bruna tells us her zika infection happened when she was 12 months pregnant. The last in her family to get it but they were all sick. Fever, headache, rash. Nobody imagined it could affect her baby. When during your pregnancy did you know that there was a problem with Anna Beatrice? Translator: Never. Reporter: Anna's condition wasn't picked up until the sudden silence in the delivery room. Doctors told her Anna would only live for a day but she's defying the odds. She's looking at you. Does she recognize you? Translator: Uh-huh. Reporter: Every case of microcephaly is different but many doctors and scientists say the big rise in cases has a common cause. A mosquito carrying the zika virus. 80% of those infected with zika don't feel sick, no symptoms at all. But for those who are pregnant, evidence is growing that it can be a disaster. To control this outbreak the government is trying to reach 50 million houses across the country every month, sending in the military and public health teams, going door to door, looking for anywhere mosquitos could breed. For a country this size, that's a monumental task. There's no cure. No treatment for zika. So the Brazilian government is trying to control the epidemic the only way it can -- Every house in this area is visited at least once a month by the soldiers to look for any place a mosquito could breed. So if a soldier knocks on the door you have to open up. We follow one soldier on his inspections. He's even looking to see where the water drains out of the refrigerator, the condensation, to make sure there's no pooling water. That's all it would take for mosquitos to breed. He's putting a chemical, a larvicide on top which will kill those and hopefully will last and protect this water until the next time he comes. Like everyone in Brazil these days we apply mosquito repellent constantly. But the virus is on the move. More than 50 cases so far reported in the U.S. All travel related. Lizzy morales, a Houston mother, contracted zika on a Christmas visit to El Salvador. You could see bumps in my lips. My eyes. My ears. You have no strength, no energy. Like to do anything. Not to even sit down. All you want to do is lay down and sleep. Reporter: She wasn't pregnant. Her symptoms subsided. Since the virus is believed to leave your blood when you recover any future pregnancies should be fine. Today Florida governor Rick Scott declared a public health emergency in four counties where people have been diagnosed with zika. Red cross is telling donors to hold off giving for 28 days if they've been somewhere that has zika transmission. Yesterday the first confirmed case of zika transmission in the U.S. Spread not by mosquito but through sexual contact with someone infected by the virus. Dr. Peter hotez, a tropical disease scientist, said blood transfusions and sexual contact should be the least of our concerns. The case of sexual transmission is a bit of a red herring. Our efforts need to be focused on preventing mosquito bites. Reporter: Hotez says he's very worried about zika spreading in areas like this one, the heart of Houston city limits. Lots of discarded tires that are thrown out by the side of the road. These discarded tires after a rain will fill with water and fill with leaves and other debris and this makes the perfect mix for mosquito larvae to breed and develop. And then they'll become adult mosquitos and then they're going to fly across to all the houses that have no window screens, no air conditioning. So all of these factors come together to create that kind of perfect storm. Reporter: He says that just like the shanty towns in Brazil, impoverished areas here are prime breeding grounds for mosquitos. In many respects this looks like the public health movie you show to first-year medical students, public health students. But it's not in a developing country, it's right here in Texas, here in the united States. Reporter: Back in Brazil, we toured a place where some scientists are undertaking a radical experiment to reduce the kind of mosquitos that spread diseases like zika. Goal is to create a line of mosquitos that die before they can bite people. We are in a mosquito factory. This building here, it produces 2 million male mosquitos genetically modified every single week. Only female mosquitos bite people. These males were ol teared so their offspring will die before they can bite anyone. After they reach maturity they're sprayed out the window of a van. They mate with the females in the community and the offsing die, offspring day, reducing the spread of the disease. 25 million mosquitos have been released. The number of mosquitos that can spread disease has gone way down. They said they're all male and male mosquitos don't bite. I hope that's the case because there's 245,000 of them. The long-term impact of this experiment isn't yet known. These mosquitos are not approved for use in the U.S. And critics worry that messing with genetics may not be safe. Microcephaly isn't the only concern when it comes to zika virus. A debilitating form of paralysis has been on the rise in places with zika. The big question, though, is whether zika is the cause. To answer this, Dr. Ashley sachinsky, first-year detective with CDC, took us with her as she conducted an investigation in partnership with the Brazilian health ministry. Her team gathers data and blood samples. Looking for a possible link between the zika virus and this rare and devastating condition. What's it like to do what you're doing? Well, it's -- humbling. Because of the significance of the public health problem. But it's also sort of exciting to be on the investigative side and figure it out in realtime. Reporter: The summer olympics now just six months away, and so many questions remain. Preparations have begun, including fumigating the main stadium for mosquitos. Late last week, Rio's olympic committee said they were confident athletes in Brazil will be completely safe. But American wrestler Alisa Lape, who is in Rio training for the games, isn't so sure Vinita Nair she says she's being cautious. Wearing bug spray, I guess. I haven't really been outside the hotel. I think that's really helping. Yeah. It's kind of scary. Reporter: The reality is we are just starting to learn about zika virus, about its effects, and how to fight it. We don't yet know either what proportion of the children born with microcephaly have it because of zika, and whether there are other conditions besides micro civcephaly that may be associated with zika. Reporter: As the dancers prepare for carnival, a worried Brazil wonders, where do we go from here? For "Nightline" I'm Dr. Richard Besser, Brazil. Up next, the presidential

This transcript has been automatically generated and may not be 100% accurate.

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