hailed as a hero >> announcer: this is "nbc nightly news" with lester holt good evening, everyone vice president kamala harris is isolating at home tonight after joining millions of americans who have tested positive for covid-19 the white house says she does not have symptoms and her list of recent close contacts does not include the president or first lady whom she last spent time with over a week ago. tonight as new covid cases in the u.s. continue to trend upward, deaths and hospitalizations remain lower even as the country gradually lowers its guard, learning to live with covid. many, including vice president harris, counting on vaccines and boosters to protect against severe illness. the news breaking as the cdc today offered a stunning glimpse into how many lives the virus has touched. new data revealing more than half o americans have shown evidence of the virus infection. kristen welker has much more. >> reporter: tonight, america's most powerful woman contracting covid-19 the white house announcing vice president kamala harris tested positive on both rapid and pcr tests this morning all unfolding just before she was scheduled to meet with president biden in the oval office. harris tweeting, today i tested positive for covid-19 i have no symptoms, and i will continue to isolate and follow cdc guidelines i'm grateful to be both vaccinated and boosted. >> she is boosted, actually twice-boosted, right we have a very, very contagious variant out there. it is going to be hard to ensure that no one gets covid in america, that's not even a policy goal. >> reporter: according to the white house, the last time the vice president saw president biden was last monday at the easter egg roll. and mr. biden tested negative yesterday it comes as the cdc reports as of february, nearly 60% of americans have been exposed to covid almost double the amount seen in december of last year. and late today, pfizer is asking the fda to approve a booster shot for children ages 5 to 11 the white house covid coordinator calling this moment an inflection point and was asked, is it just a matter of time before the president gets covid too >> i wouldn't say it's a matter of time, but of course it is possible that the president, like any other american, could get covid. the bottom line is he is vaccinated and boosted, he is very well protected >> kristen, what do we know about the treatment the vice president is receiving? >> reporter: lester, we asked the vice president's office whether she's taking any therapeutics or other treatments her aides declined to answer meanwhile, white house officials tell us there are no plans to change the covid protocols here lester >> kristen welker, thank you. new fallout from the war in ukraine russia suspending natural gas supplies to poland and bulgaria as its forces step up their assault on eastern ukraine. kelly cobiella is there for us. >> reporter: tonight, ukrainian troops trying to hold the line in the east, now facing an intensifying russian assault. in mariupol, authorities say russian forces have hit a steel plant 35 times in 24 hours. it's the last holdout of ukrainian troops there. the city's mayor says a third mass grave has been discovered and that locals are being forced to bury bodies in exchange for food and water. and tonight, russia is taking new actions outside ukraine. now cutting off natural gas deliveries to poland after poland refused russia's demand to pay in rubles poland like much of europe is still buying russian oil and gas and has been sending ukraine weapons. today in germany, u.s. defense secretary lloyd austin meeting with defense officials from 40 countries, pushing for more military support for ukraine. >> ukraine clearly believes that it can win. and so does everyone here >> reporter: and u.s. officials now tell nbc news that american intelligence-sharing at the beginning of the russian invasion helped ukraine move its aircraft and air defenses out of harm's way. all of it comes after those stunning comments from russia's foreign minister overnight, saying the u.s. and nato are fighting a proxy war, warning the risk of world war iii is real. "i don't want it to be blown out of proportion," he said, "but it should not be underestimated." ukraine's foreign minister responding, this only means moscow senses defeat. but in the east, fears russia is tightening its grip in kherson where locals resisted the russian occupation weeks ago, signs of a complete takeover. president zelenskyy accusing the russians of laying the groundwork for a sham referendum to declare kherson's independence, calling it shameful. in kyiv, the anger for russia now so deep, statue meant to mark the bond between russia and ukraine now being brought to the ground >> kelly joins us now from dnipro. kelly, today the biden administration says they're now able to get those weapons to ukraine faster with states over its plan to end covid restrictions at the southern border, the supreme court took up another controversial immigration policy today, the one forcing asylum seekers to wait in mexico. with more on that, here's pete williams >> reporter: president trump called it the migrant protection protocol, requiring immigrants from central america seeking asylum to wait just outside the u.s more than 68,000 were shuttled back to mexico, tent cities sprang up along the border human rights groups said hundreds were kidnapped and assaulted. in one of his first actions after taking office, president biden shut it down, but texas and missouri sued saying the trump program helped stem the surge at the border and claiming the government didn't follow the law in shutting it down so a judge ordered it started back up. the government says congress has never provided money for enough detention space at the border so thousands of immigrants can be allowed to wait inside the u.s. evaluated on a case-by-case basis on the supreme court justice samuel alito said that's probably no more rigorous than screening baseball fans entering nationals park >> you've got a little checklist, boom, boom, boom, that's how you can process. maybe you're right but that's what you think congress meant by a case-by-case determination? >> reporter: but several justices noted that stock sinking 12% just today >> with his priorities, can elon make it a better, more successful business? >> when you're doing all these incredibly difficult things, he lands rockets in platforms in the middle of the ocean. he's good at challenges he single-handedly moved forward the electric car industry. everybody else has been chasing him >> reporter: musk's passion for twitter has earned him the support of twitter co-founder and fellow billionaire jack dorsey, tweeting, elon is the singular solution i trust, adding, this is the right path, i believe it with all my heart the open question is whether users will feel the same. jo ling kent, nbc news, los angeles. tonight, a family demanding answers and filing a wrongful death lawsuit after their son fell from his seat on a 400-foot-high amusement ride sam brock now with late details >> reporter: tyrece samson's mom called him her personal teddy bear, a gentle giant who left for spring break in late march never to return. >> i couldn't hug him, i couldn't do anything i don't wish that on any parent any parent >> my son was tyrece, 14 years old he's been taken away from me. >> reporter: the depth of pain for mother and father now transformed into legal action. after their son died riding the recently opened 400-foot orlando freefall ride, coming right out of his seat the pair jointly filing a wrongful death lawsuit which names icon park, the manufacturer, and the ride owner, slingshot, claiming system-wide failure, alleging the operator negligently adjusted restraint systems on the freefall ride, failing to train their employees, failing to provide a safe amusement park ride. >> this tragedy could have absolutely been avoided very simply, with one thing with this $22 seat belt if it had been employed as a secondary restraint. >> reporter: icon park, where the ride is located, declined to comment on the lawsuit and the manufacturer couldn't be reached but an attorney for slingshot, which owns and operates the ride, told nbc news in part, orlando slingshot continues to fully series "climate challenge" and the explosion of devastating wildfires. we're on the front lines of the battle to stop them from happening in the first place. we're back now with a dangerous start to fire season right now, 11 large fires are burning across six states, scorching more than 200,000 acres combined now there is a massive effort to stop these >> firefighters are beginning to lose the battle. >> reporter: after year. >> the air attack has been a major asset all day long. >> reporter: after year. >> the winds fanning these flames are expected to last another 24 hours >> reporter: in 2021, oregon's bootleg fire tore through the jacobs family property. >> the fires have got unreal big from what they was back in the past >> when it's burning, can anything slow it down >> no. >> reporter: the fifth-generation loggers and ranchers lost 300 acres now the federal government is trying to help families like theirs, urging them to thin their own forests before fire season begins, or to initiate prescribed burns, controlled fires like this one, so there's less wood to fuel the flames when fire season starts. but conducting these burns isn't cheap or easy >> who pays for that >> that's the thing right there. if we'd have managed our own property, done this thinning and stuff behind us, and then possibly had the state come in and do underburns and stuff like that, it would have saved our ground. >> reporter: across the u.s., there are 765 million acres of forest land. extreme drought and climate change creating the most explosive conditions in the west. the government now wants to reduce fuel and clear as much land as the size of idaho to tackle that, last fall's infrastructure bill included billions set aside to fight wildfires before they start. >> when you look out here and see all these trees, do you see beauty or do you see danger >> both. you know, i wish we could thin it all. >> reporter: here in oregon, forest thinning can cost up to $900 an acre. government grants help, but there's not enough money to go around the jacobs family has applied for federal funding, but for now, they're covering their own bill on a property this size it's roughly $1 million, something they can't afford. but the cost of a catastrophic wildfire is even greater. just a few miles away from the jacobs ranch, the dollingers' property was also burned but they're taking part in a ten-year program with the oregon department of forestry so a >> reporter: which is why they're investing test test under district attorney gascón, i prosecuted car break-ins. all repeat offenders, often in organized crime rings. but when chesa boudin took office, he dissolved the unit and stopped me from collaborating with the police on my cases. now home and car break-ins are on the rise because repeat offenders know they can get away with it. chesa boudin is failing to do his job. there's a better way to keep san francisco safe. recall chesa boudin now. a major change to tell you about on aspirin guidelines for years doctors have recommended daily aspirin to reduce the risk of a first heart attack or stroke but a top task force saying today, most people 60 and older should no longer take it regularly due to a risk of internal bleeding and the group now says people 40 to 59 should only take aspirin daily if they have a higher risk of heart disease. also tonight, a major military housing contractor under fire on capitol hill after an eight-month-long senate investigation found mismanagement put the health and safety of american military families at risk here's garrett haake. >> reporter: captain samuel cho said his family was living in their home on georgia's fort gordon for only two months when his 8-year-old daughter developed a severe rash. >> her skin became hardened and rough and reptilian in nature, where if she were to scratch it, it would break easily and she would bleed profusely. >> reporter: a base physician diagnosed severe atopic dermatitis blaming mold in their home a likely cause. kicking off a months-long battle with the housing contractor balfour beatty investigations today citing numerous instances in which the company failed to properly respond to both repairs and environmental hazards, including mold technical sergeant jack satorres was forced out of his home on a texas air base for 12 weeks of mold removal. >> these displacements caused my family great amounts of distress, as you can imagine. >> reporter: last december, balfour beatty pleaded guilty to major fraud against the united states. ordered to pay $65 million in fines and restitution. today the company executives on the hot seat. >> why should we believe that a company that engaged in major fraud against the united states is fixing this? >> i reject the suggestion that it's a systemic failure things go wrong. we don't always get it right the first time we're not perfect. >> reporter: now stationed in south korea, captain cho flew 7,000 miles to make sure these failures would be the last. >> no one else will speak up for my daughter. >> reporter: garrett haake, nbc news, the capitol. up next, meet a four-legged war hero in ukraine with a nose for potential danger finally, he's not only a best friend to his owner, but to ukrainians he's never met. and those whose lives he may have saved. here's erin mclaughlin >> reporter: his name is patron, or "bullet. in ukraine, he's known as a hero. the pint-sized jac russell terrier specially trained to sniff out land mines left behind by the russians every day he's working, his owner mihail says. we met patron outside the northern city of chernihiv. where they're clearing the area of the remnants of war. ukrainians forces may have pushed the russians out, but what the occupation left behind is potentially just as deadly unexploded ordnance and mines, too many to count. patron helps collect them before detonation how many lives has he saved? "impossible to know," he says. one mine can kill one person or several people we're told the number of mines he's discovered is a secret mihail says he purchased patron two years ago as a gift for his son. "i took him with me to work one day," he says "he showed his skills, it was an accident." now patron is famous with over 100,000 followers on instagram. posts showing him hard at work, or at play with his trusty stick. he's also known for comforting other emergency service workers who might be having a bad day but sometimes all the attention can be too much nothing a few treats can't fix before he returns to potentially save more lives on the front lines. erin mclaughlin, nbc news, chernihiv, ukraine. >> dangerous work for man and beast. that's "nightly news" for this tuesday thank you for watching, everyone i'm lester holt. please take care of yourself and each other. good night . i'm raj mathai. next on nbc bay area news tonight after a gut wrenching 20 hours baby brandon is home tonight. but who kidnapped the 3-month-old and why? we have exclusive video and details. >> this suspect appeared at the residence with a baby carrier. we do believe this was planned. it wasn't some random act. >> we're piecing together how and where the baby was found and speak to the quick thinking good samaritan who called police. and our newsroom. >> my heart is overwhelming because this was a bad situation that turned good. >> also vice president harris tests positive for covid just days after her bay area visit.