Hunger has no tipping point. It’s too blunt for that. A child has enough to eat and has the energy to grow and think and learn. Or she doesn’t.

But our perceptions about hunger can reach a tipping point: it’s the moment we begin to connect the global headlines–and feel a wave of worry.

It started for me last week with a story in the New York Times about a blight along the shores of Lake Victoria in Uganda that’s ravaging the cassava, a tubby white tuber that is a staple there—and for 800 million people on our planet.  Called brown streak, it mottles the tubers with clumps of brown that look like rot. The virus is a mutation of one that has plagued farmers on Tanzania’s coast for seven decades, but this new invader is now marching through inland fields around the lake and could bring devastation to small farmers across East Africa. And if it jumps shores—to Asia or South America—millions more could be affected.

I first saw fields of cassava, also known as manioc, on a visit to the eastern provinces of the Democratic Republic of Congo. It was sprouting, hardy and drought-resistant, in a hodge-podge of plots surrounding the huts in Kotoni. Ngabu Safari Jean yanked a green stem from the earth and showed me its root. I understood enough from his gestures to know that it was an important source of food in his community—and represented security in a place that has known so little.

It’s a staple in Haiti, too, hawked by roadside vendors selling it in plastic baggies to carloads of people chugging out of Port-au-Prince. A photographer I was with recently on a field visit brought a plump sack of it from one of them, her mouth watering as he passed it through the window. She loves it, she said.

A blight on this simple but essential food is the last thing hungry Haiti needs as it continues to reel from the January earthquake. And it’s feeding my worry about another looming hunger problem: nearly 10 million people in West Africa are facing a food crisis brought on by irregular rains last year that left farmers with poor harvests, shriveled pastures, and a shortage of water. Worst hit is Niger, where the harvest is 26 percent smaller than the year before and eight million people are now at risk. Oxfam is distributing food and supplies in the most vulnerable regions.

The final connection came yesterday when a colleague circulated an Associated Press story about the toll high food prices are continuing to take on people in poor countries—two years after we’ve all but forgotten about the food crisis that had a stranglehold on the globe in 2008, a crisis severe enough to topple the Haitian government when riots broke out over skyrocketing prices. People there had resorted to eating meals of mud patties mixed with sugar and oil to stave off hunger.

The AP story quoted Majeedan Begum, a mother of five children, who lives in Multan in Pakistan. Bread is the main staple for her family, but today a sack of flour costs three times what it did two years ago—a spike so sharp she can no longer afford to buy meat or fruit.

But it’s when the threat of hunger is close to home that worry turns to something else: fear. A woman I chanced to meet yesterday—close in age to me and living in a town near mine–spilled what she could no longer hold in. On Friday, her son, the young father of a brand new baby, was laid off from his job behind the reception desk at a hotel, a job that paid him just $11 an hour—barely enough on which to support a family. He was among the working poor, said his mother.

And now?

She urged him to set aside his pride and his sorrow—even as her own weighs heavily—and apply for food stamps to feed his family.