Transcript for The race against time to save 20 million in Somalia, South Sudan, Nigeria and Yemen from starvation

Finally tonight here, you saw so many of the children right here. Children at risk of starvation. Four countries on the bnk of famine. We witnessed devastation, but also the smile when is that much-needed help arrives and tonight a joint global response never seen before. Reporter: We took you along on our journey, that eight-hour trek across somali land, and doctors are still in a race against time. We saw this 2-year-old weighing just 11 pounds. The nurse working telling us at the time he was so weak they feared she would die within minutes after arriving. More than 100 miles away, another hospital. We won't forget this doctor and what he told us. You are on the verge of famine. That's what I believe. You are seeing it? It's here. Reporter: This child lost the strength to talk. His tiny hand in mine. Eight U.S. Based relief organizations are now joining forces to get the word out that urgent help is needed in Somalia, South Sudan, Nigeria and Yemen. More than 20 million facing starvation. Actor George Clooney lending his voice. Americans are the most generous people on the planet. Helping others is engrained in our spirit. Reporter: So many at home already proving that. Giving nearly $2 million in donations after our report. Now creating a hunger relief fund saying $2 can provide water at school for a month, and $1.30 can help a child recover in South Sudan. You're sounding the alarm. We need people to realize what's going on across these four countries. We can make a difference for these kids if we act now. Reporter: Children being helped by so many of you. Thank you for watching here on a Wednesday night. I'm David Muir. I hope to see you right back here tomorrow.

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