the run. also breaking, the deadly shooting. chaos erupting at a packed event. police rushing to the scene. and the zika virus on the rise. 36 cases discovered in a dozen states. dr. rich besser with the military going door to door in the heart of the outbreak. and, bringing down the house. the dream home on the hill, and the nightmare discovery forcing them to tear it down. >> announcer: from abc news, this is a special edition of "world news tonight," reporting from iowa, cecilia vega. good evening. thank you for joining us on on this saturday. as we come on the air tonight, the state capitol right here behind me and the countdown to the iowa caucuses is on. you can feel the energy all across this state and the candidates are everywhere. take a look at this map. the presidential hopefuls making 57 different campaign stops today alone. and on the republican side, so

donald trump jetting in on his personal plane today, ted cruz on track to visit every county in the state. and now, marco rubio with the momentum. our team is right here covering it all and abc's tom llamas starts us off. >> reporter: donald trump and his private jet making a flash landing into iowa. the crowd waiting, not his largest, but ready for their caucus-marching orders. >> so, this is now crunch time. this is it. this is what it's all about. so we have to get out there and caucus, and do all of the things that we have to do, or we've all wasted our time, folks. >> reporter: trump also making his push on social media, reminding evangelical voters he owns a bible and loves it. >> and it's just very special to me. and, again, i want to thank the evangelicals. i will never let you down. >> reporter: and ivanka trump a born and bred new yorker now out with an infomercial for iowans. >> hi, iowa, i'm ivanka trump

you how to caucus for my father. it's a secret ballot. you just write down the name "trump," and you are done. and that's it. >> reporter: trump also not letting up on his birther attack against senator ted cruz. can fadian born. >> now they're saying you just can't run, you can't run. >> reporter: cruz trying to laugh off those attacks. >> i will say this, when donald trump insults you, it's amusing. >> reporter: but to donors cruz admitting trump is getting to him. cruz writing in a fund-raising letter today, "the latest polling shows that donald's attacks are swaying voters." and with just two days left, cruz going hardest not on trump but on senator marco rubio. >> when he got to washington he made the decision to lead the fight to pass amnesty. >> reporter: rubio telling voters cruz may lose in iowa and is now in panic mode. >> he's decided to run a very

>> reporter: in a rare move, the rubio campaign is launching a 30-minute tv special profiling rubio, a similar move to what president barack obama did in his first run for presidency in the general election. tonight, donald trump rallies tonight with jerry falwell jr. who he hopes will help him with those evangelical voters. cecilia. >> tom covering this campaign thanks tom. for the democrats in this final sprint the two front-runners today, seeming to take the gloves off. hillary clinton's campaign turning into a family affair with husband bill and today, daughter chelsea right there, too. bernie sanders also speaking to packed halls. but tonight, the big question, what is hillary clinton saying about those top-secret e-mails. abc's jon karl. >> reporter: hillary clinton campaigned today in ames, iowa, with some of her most high-profile supporters. daughter chelsea and gabby giffords. >> speaking is hard for me.

these two words. madame president. >> reporter: mrs. clinton needs all the help she can get as she faces a tougher than expected race in iowa. as she rallied the crowd no mention of the story hanging over her campaign. the state department now says there was top-secret information and 22 of the e-mails sent from her private account. as of secretary state. >> why was there top-secret information on your e-mail? clinton told cnn nothing had changed. >> i didn't send or receive any e-mails that were classified. >> reporter: bernie sanders had nothing to say about the e-mail issue as he made his final push. praising iowa democrats for what they did eight years ago when barack obama scored an upset win over hillary clinton here in iowa. >> thank you, iowa, for leading the country in that direction. >> reporter: when we caught up

2008 slogan, yes we can. >> one of the problems we have had jonathan, people say, i like bernie and his ideas but he can't win. >> reporter: so, can you win? >> yes, we can. many polls out there suggest that we can beat people like donald trump and beat him pretty badly. >> reporter: every campaign event is packed. here in ames, hillary clinton, they're up here in the upper deck cheap seats, anywhere they can go and still get a glimpse of the candidate. the final weekend means crunch time for the volunteers. you're not running out of stickers, i can see. >> we'll never run out of stickers. and jon joins us now here in iowa, jon, polls have shown that one of clinton's biggest challenges is trust. so, what are voters out there telling you about this latest e-mail controversy, will it hurt her? >> well i'm not hearing

saying they're not worried about the e-mail issue. it could cut into one of their central arguments. one of her arguments is she's most likely to win in november. >> not what she wants to be talking about right now. jon, thank you. the race is tight on both sides tonight. and turnout at the caucuses will make all the difference. it's sure what candidates say at every rally counts the most and so does their operation to get out the vote. abc's david wright with the last-minute ground game. >> reporter: crunch time here in iowa, so the volunteers are pounding the pavement. >> thank you. >> reporter: knocking on doors. leaving calling cards and sometimes striking out. >> caucus on monday? >> no, we won't be here. >> reporter: this husband and wife came here from dallas to help out. what is it that would make you come all this way for them? >> it's time that we kind of fit our time -- >> reporter: people are coming from far and wide.

have you ever done this before? >> no. >> reporter: where did you come from? >> phoenix. >> reporter: you drove from phoenix? >> starting yesterday morning. >> reporter: they said the democrats they're meeting seem pretty happy with their choices. >> kind of voting for bernie, but if it comes down to the other way, i'll vote for the other one. >> reporter: the republicans are passionate, too, but some nervous. at trump's rally in dubuque -- lot of trump voters out there today. some of them just interested in catching a glimpse of him. the crowd here in cedar rapids, getting ready for a bernie sanders rally about to start. state officials say they're preparing for an avalanche of caucus-goers. there are some out there that haven't made up their minds. cecilia. >> the great undecided. david, thank you. a reminder tomorrow on "this

donald trump, bernie sanders and hillary clinton. also, david muir joins us here in iowa tomorrow for another special edition of "world news tonight." but we do now move on to our top story, that breaking news from california. two more escaped prisoners caught. tonight, all three back behind bars, thanks to a lucky tip in san francisco. it led to this stolen van, one inmate caught after the chase, the other caught hiding right also in that van, ammunition. abc's matt gutman with how this capture went down. >> reporter: tonight, that chaotic chase in downtown san francisco. a bystander spotting that white gmc van. >> officers approached the van, as hossein nayeri fled the area on foot. >> reporter: police in pursuit. it's hossein nayeri wanted for torture and kidnapping. >> he's running eastbound up

>> reporter: then. but murder suspect jonathan tieu is still in the van. >> that van right to your 5:00, can you stand by? there might be another person in there. standby, take a look in that van. >> reporter: he's arrested without incident. found in the van at least three rounds of ammunition but no gun. the three escapees busted out of the orange county jail last weekend. nayeri had apparently enlisted the help of a jail english teacher. with whom he exchanged loving letters. >> we do know it was much closer, much more personal than it should have been. >> reporter: shortly after the jailbreak, bac duong steals that van spotted today. on friday he casually surrendered. investigators are now searching for a possible gun to go along with the ammunition they found and for possible accomplices.

this, those two felons caught today face only three additional years in prison for that jail break. another breaking story tonight, gunfire at a conference person dead, several others injured. the violence breaking out at a motorcycle expo. abc's ron claiborne on what we know at this hour. >> reporter: it happened just before 1:00 this afternoon. >> shots fired at the coliseum, at the motorcycle rally. >> reporter: early details were sketchy but it appeared someone fired shots and stabbed a number of people in what police are calling a disturbance at the colorado motorcycle expo. the show attracts a large number of bikers. >> we have one deceased party and multiple victims that were taken to the hospital. >> reporter: officials say that at least seven people were being treated at the denver health medical center. an extremely heavy police presence outside. police say they're questioning one person, but at this hour, no one has been arrested.

of violence still under investigation tonight. ron claiborne, abc news, new york. and next tonight, inside the desperate battle against the zika virus. here at home, reports of 36 people contracting the disease in a dozen states, four of them pregnant women. but tonight, the urgent fight to stop the epidemic at its source and this's where we find abc's chief health and medical editor dr. richard besser is >> reporter: door to door, they're desperate to what the explosive growth of zika. there's no vaccine, no treatment. all we know is mosquitos carry it. so, soldiers are scouring neighborhoods. there's a government requirement that every house is in this area is visited at least once a month by the soldiers. they're meticulous.

drains out of the refrigerator. in these towns, residents store water in large tanks. often neglected. soldiers sanitize each tank. at this clinic, we see firsthand why the stakes are so high. >> this is scary. we're dealing with a disease that we have no information about. >> reporter: these babies have abnormally small heads and brains. there are hundreds of cases here. more than 4,000 in brazil. scientists suspect they're directly connected to a zika virus infection during pregnancy. but we don't know how. health officials are bracing for more. until zika virus is under control in brazil and the other countries in which it's spreading, the cdc says it's far too dangerous for pregnant women to travel to those areas. they should stay home. cecilia. >> a good warning, dr. besser. thank you to another health emergency

flint, michigan, families there being told even filtering their water will not make it safe to drink, the lead levels way too high, and tonight, a bombshell e-mail. after the water troubles there began, city officials were given bottled water, but what about all those families? here's abc's alex perez. >> reporter: embattled michigan governor rick snyder is facing harsh criticism tonight for the latest revelation in flint's ongoing water crisis. e-mails exposed by progress michigan, reveal the state shipped bottled water to its workers in flint, over eight months before residents were officially told the drinking water was unsafe. governor snyder's reply. >> i had no knowledge of that taking place. >> reporter: the e-mails included a department memo, which said coolers will be provided as an option. quote, "as long as the public water does not meet treatment requirements." this city had warned sick and elderly residents of potentially harmful chemicals in the water,

otherwise safe to drink. the state defends their decision, saying they only provided bottled water to employees temporarily until that particular chemical threat was over. dangerous levels of lead were later found in flint water, and about 200 kids so far have tested positive. >> knowing that someone did this to my kid, it's hard. i can't sleep at night. >> reporter: and tonight, officials are now warning that the filters they handed out to residents may not be effective enough to keep their water safe. alex perez, abc news, flint, michigan. there's still much more ahead on this special edition of "world news tonight." the dream home suddenly a nightmare. the dangerous discovery that brought down this house. and facebook is stepping into a hot debate, the new ban

users. look, the wolf was huffing and puffing. like you do sometimes, grandpa? well, when you have copd, it can be hard to breathe. it can be hard to get air out, which can make it hard to get air in. so i talked to my doctor. she said... symbicort could help you breathe better, starting within 5 minutes. symbicort doesn't replace a rescue inhaler for sudden symptoms. symbicort helps provide significant improvement of your lung function. symbicort is for copd, including chronic bronchitis and emphysema. it should not be taken more than twice a day. symbicort contains formoterol. medicines like formoterol increase the risk of death from asthma problems. symbicort may increase

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down. the house sliding down the hill threatening the neighborhood. here's abc's aditi roy on the mystery in san francisco. >> reporter: tonight, a dream destroyed. >> it's one of those devastating kind of pieces of news. >> reporter: ronald martell hadn't even moved into his san francisco home, when he discovered it sliding downhill, threatening the neighborhood below. his only choice, tear it down. it's not just this home that was five others were also on this and now, those homeowners are worried they could be next. >> you wake up one morning and the comment is, you may have to lose your home. >> reporter: tonight demolition is almost done, still no one knows what triggered the slide. but already, martell is hopeful he'll be able to rebuild. >> for californians we rebuild >> reporter: no other homes are

but homeowners nearby are required to hire an engineering firm to prove their houses aren't at risk. or face the wrecking ball as well. cecilia. >> aditi, thank you. still ahead on "world news tonight" -- facebook, in one of the most contentious issues in america. what users can no longer do. and it's beyonce like we have never seen her before. but why is this new video sparking so much outrage?

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straight now to the "index," facebook jumping into the gun control debate, banning private gun sales on its site and on instagram. the decision blocks person-to-person sales. which allowed people to avoid background checks. next, to a stunning loss on the court for defending champion serena williams. that defeat means a first major australian open win for germany's angelique kerber. kerber admitted she had goose bumps facing off against the number one player in the world. and could this be a super bowl preview? ahead of their joint halftime show, coldplay and beyonce releasing this video of their new collaboration, that's queen b. right there herself, starring as a bollywood goddess. the video is sparking heated debate online. many indians calling it an insult to their culture. and when we come back -- the

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those caucuses. we came to drake university. hi, you're the caucus expert? to ask that burning question. what the heck is a caucus? it's complicated, so they gave us a demonstration. for the democrats, groups of iowans gather to choose delegates who then go on to choose their party nominee. one side tries to convince the other to join their team. or a break tie with food. or -- >> rock paper scissors. >> the republicans have it a lot easier, they write down a candidate's name on a slip of paper, and done. if it sounds like a bunch of song and dance. well, there is a caucus musical. iowa >> reporter: but just remember, iowa launched presidential runs for jimmy carter, two george bushes and barack obama. and come monday, they may just launch the next leader of the free world.

"good morning america" and "this week" in the morning. david muir anchors right here

i'm cecilia, good night. music ] >> announcer: the following program is sponsored by operation smile. every year, hundreds of thousands of children are born with cleft lip and or cleft palate. >> dr. bill magee: why should any child, anywhere on this planet, have to live a life of misery. >> kathy majette: a lot of people think that children that are born with these deformities are cursed. just imagine a life alone, that nobody wanted to be around you. >> norrie oelkers: and we had children coming in for screening with brown bags over their head. they're never allowed to leave their house unless they have a bag on their heads. >> kathy majette: some children don't live,