Nissan. Innovation that excites. Seconds. Good evening. Thanks for joining us. The mysterious disease causing international anxiety. Were 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. Heres abcs chief medical editor dr. Richard besser. Reporter 3monthold Anna Beatrice, whos like any normal baby but anna was born with microcephaly, an extremely small head, due to abnormal brain 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. Annas 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 annas condition wasnt picked up until the sudden silence in the delivery room. Doctors told her anna would only live for a day but shes defying the odds. Shes looking at you. Does she recognize you . Translator uhhuh. Reporter every case of 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 dont 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, thats a monumental task. Theres 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. Hes even looking to see where the water drains out of the refrigerator, the condensation, to make sure theres no pooling water. Mosquitos to breed. Hes 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 wasnt 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 theyve been somewhere that has zika transmission. Yesterday the first confirmed 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 hes 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 theyll become adult mosquitos and then theyre 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. 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 firstyear medical students, Public Health students. But its not in a developing country, its 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 of a van. They mate with the females in die, re spread of the disease. 25 million mosquitos have been released. The number of mosquitos that can spread disease has gone way down. They said theyre all male and male mosquitos dont bite. I hope thats the case because theres 245,000 of them. The longterm impact of this experiment isnt 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 isnt 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, firstyear 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. Whats it like to do what youre doing . Well, its humbling. The Public Health problem. But its 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, rios 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, isnt so sure vinita nair she says shes being cautious. Wearing bug spray, i guess. I havent really been outside the hotel. I think thats really helping. Yeah. Its 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 dont yet know either what proportion of the children born with microcephaly have it because of zika, and whether there are other conditions besides micro civilcephaly that may be associated with zika. Prepare for carnival, a worried brazil wonders, where do we go from here . For nightline im dr. Richard besser, brazil. Up next, the president ial candidate giving Hillary Clinton a run for her money. And later, the superstar joining a chorus of past performers singing americas anthem at the super bowl. Dad, you can just drop me off right here. Oh no, ill take you up to the front of the school. Thats where your friends are. 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You cant buy bernie reporter here as they would put it to feel the bern. Feel the bern reporter Bernie Sanders campaign is on fire right now. Frontrunner to win the New Hampshire primary if you want a government that represents all of the people and not just a few, come on board reporter and but for the flip of a coin or two he came awfully close to winning the Iowa Caucuses too. Tails. It looks like we are in a virtual tie. Reporter the 74yearold junior senator from vermont, the only democratic socialist in congress, now giving Hillary Clinton a serious run for her money. His campaign raised 3 million in 24 hours after iowa. Integrity and authenticity are words his supporters use. Feels good to have somebody around that feels worth getting passionate about. There are a lot of conversations that hes presenting that we need to be having in this country. Bernie talks about attacking the corrupt Campaign Finances, he talks about raising the minimum wage to a living wage, he talks about bringing back manufacturing, he talks about infrastructure. Reporter a political rise nobody but bernie saw coming. When i first met him a year ago, he was just considering whether to throw his hat into the ring. In it to articulate positions . That i know the answer to. If i ran, i would run to win. I know if i do this, i start off as a significant underdog. 70 of the American People dont know who Bernie Sanders is. The word snowballs chance comes to mind. No offense. Reporter hes out there raising fundamental questions about the american political system and the u. S. Economy. A system he says is rigged in favor of billionaires and bankers. We the people are going to have to have a government that represents all of us, not just a handful of billionaires. Reporter he rails against the 1 and the politicians they keep in their pocket. His platform straight out of occupy wall street. College education freeforall americans. Health care free for all americans. Hed break up the big banks, raise the minimum wage, and fund all this by raising taxes on the rich and on corporations. Or do you think this is a minutable fight . I dont want to tilt at wind mills. There are so many people who are hurting, working longer hours for low wages, and the billionaires are getting richer. They need a voice. Reporter Bernie Sanders has given them a voice. And hes put his money where his mouth is. Theres no super pac aligned with his campaign. Instead, hes funding it with record numbers of small donations. 3. 25 million of them. Average amount 27 apiece, according to his campaign. Hes an unlikely messenger, easily parodied by snl the other candidates are taking millions from the coke brothers and exxonmobil. But not me. I only accept coins. Im not talking about fancy coins like dimes and quarters. I just want nickels and pennies. Reporter his Main Campaign ad features a golden oldie. Look for america reporter simon and garfunkel his events you find plenty of folks from the woodstock yes or no race. I am feeling the bern reporter also legions of younger voters. Feel the bern reporter among registered democrats aged 29 and younger, nationally sanders outpolls clinton nearly 41. I just like his ideas for wall street and what hes going to do with our future education. Its already been incredibly impressive for him. Reporter digital journalist mary alice parks has been traveling with the Sanders Campaign for months. It has been huge since the beginning. The biggest crowds were over the summer in a west coast swing, 28,000 people in portland, almost 25,000 in l. A. Very reminiscent of obama. Big change, high hopes, high dreams. Reporter sanders has pledged to fight a clean campaign, even refusing to attack clintons use of a private email server. The American People are sick and tired of hearing about your damn emails. Thank you. Me too. Reporter now hes drawing sharper distinctions. Hitting her hardest on her ties to wall street and her dependance on campaign contributions. Do you think Hillary Clinton is a progressive . Some days, yes. Except when she announces that she is a proud moderate. Then i guess shes not a progressive. It was kind of a low blow. Reporter today here in New Hampshire, clinton fired back. It was a good day for progressives when i helped to get 8 million Kids Health Care under the Childrens Health insurance program. Reporter the lowest polls show clinton trailing sanders by more than 20 points here. Clinton and others chalk that up to the fact he has the Home Court Advantage as the senator from a neighboring state. Tonight he reminded voters at a cnn town hall that Hillary Clinton voted for the iraq invasion. He didnt. The Progressive Community was pretty united in saying, dont listen to bush, dont go to war. Secretary clinton voted to go to war. Havent gotten the memo, this was supposed to be a coronation, right . No, we didnt get that memo. Reporter whats not yet clear is whether Bernie Sanders is a new and improved version yes, we can thank you, New Hampshire reporter of the force that came out of nowhere back in 2008 to take away hillarys crown. Eight years ago barack obama was here. He talked about, yes, we can. Yep. Lets be honest on a lot of things he just couldnt. What makes you think you can . People are tired of a rigged economy and a corrupt Campaign Finance system. They want real change. Thats why were doing well. Reporter back outside the colonial theater, theres no question theyre feeling the bern. I feel the bern whoo reporter im david wright for nightline in keene, New Hampshire. As for the republicans, you do not want to miss the last Republican Debate before the New Hampshire primary saturday night up next, how will lady gaga tackle singing the Gold Standard of songs at the super bowl . Lease a 2016 lincoln mkx for 399 a month only at your lincoln dealer. Ahhh the sweet taste of victory prilosec otc. One pill each morning. singing i just cant wait to meet you, sweet child youre on the way, im filled with expectation, and youre instrumental whether youre the president of the Lady Gaga Fan Club or not, there is no denying her career is on fire. Shes adding one more notch to her belt, kicking off sundays super bowl by honoring a longstanding tradition for football and nonfootball fans alike. She got plenty of applause as a pop star. But lately lady gaga has been different side. When the dog bites wowing the Academy Awards last year masterfully performing a sound of music medley. Climb every mountain teaming up with tony bennett to record an albulleting fans know anything goes. Now taking on americas anthem at its biggest game, singing the starspangled banner at the super bowl. And the rockets red glare the stakes are high. It was 25 years ago Whitney Houston belted out what many still consider to be the best pregame performance. And the home of the brave securing her place as a legend. But plenty of singers have fallen flat. Aguilera forgot the words. What so proudly we watched steven tyler delivered this rendition before the 2012 afc championship. The land of the free yeah who can forget Roseanne Barrs performance. Last gleaming something tells us lady gaga is on the edge of football glory. Out on the edge of glory thanks for watching. Tune into gma tomorrow. And as always were online 24 7 on our Nightline Facebook page good night, america. Welcome to bachelor Fan Favorites week. Today, weve got some of your favorite people from my other shows, the bachelor and the bachelorette. And theyre all looking for a big bundle of cash they can share the rest of their life with. So lets play who wants to be a millionaire. [dramatic music] hey, everybody, im chris harrison. Welcome to the show. Are you guys ready to play millionaire today . [cheers and applause] our returning contestant is known for her competitive spirit, and so far, its paying off. She was the winner of ben flajniks season of the bachelor. And today, shes here to win big sisters of central arizona