Transcript for Facing food and medicine shortages, families flee Venezuela

Next to the humanitarian crisis we've been covering for more than two years now. The mass exodus from Venezuela. Families facing severe shortages of food and medicine. Nearly 3 million people fleeing. Overwhelming neighboring countries. With Venezuela so vulnerable, Russia is moving in. Here's Matt Gutman. Reporter: These are the first Russian bombers landing in Venezuela, capable of carrying nuclear weapons. The Russians moving in with Venezuela vulnerable, and in economic collapse. Those bombers arriving as we witness the exodus on the ground. Desperate families filling this bridge to Colombia. Many of these people used to be solidly middle class, not all of them, but what is most stunning about the mass exodus from Venezuela right now is that they used to have so much. It's all gone now. We were there as the economy spiraled out control two years ago. Witnessing a country imploding. Crippling shortages of food and medicine. The danger in the streets. That's when we first met a elementary school teacher, Vanessa posada and her husband Adolfo, barely surviving. The parents would alternate which night they would eat so that their little boy could eat instead. Two years later, we find that teacher. She now says the pay is so little, she must join that exodus as well to find work to support the family. She and her husband realize she has better chance to find work. She will soon be like so many mothers we saw crossing the bridge to this border town in Colombia. At Cucuta's general hospital, we meet marly, and she shows us the picture of her little boy smiling, in better times. This is is her little boy now, in a hospital bed, struggling to eat. So many families cannot afford the next meal. And tonight, a startling number. By one estimate, in 2017, the average Venezuelan citizen lost around 24 pounds. And what the doctors tell us here is that though he looks malnourished, this is actually a sign of a boy coming back to life. It's hard to imagine that when this boy came here he was about 9 pounds, and now he's about 13 pounds. Reporter: He is slowly getting better. And she knows what comes next. A return to Venezuela, where there is no work, and an economy leaving families with no hope. She's got to go back. She has her son and her mom. And her family. When he gets better, they're going to go back. With no promise tonight that life back home will be any better. We just heard from that teacher, Vanessa, after spending Christmas with her family she's now en route to Chile, uncertain if she'll find work. Tom? Matt, thank you. There's still much more

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