South Sudan is a mess. Fighting between the government and a rebel militia has sent 25,000 people fleeing from a town called Kodok toward the border with Sudan—and on the road they've run into another 13,000 people on the run from yet more fighting. Imagine taking every person in the stands at a sold-out game at US Cellular Field in Chicago and putting them in a roadless, 104-degree desert with no high-tech means of communication, little food, and with a daily ration of just a quarter of a gallon of water each.

Humanitarian organizations providing food, water, and shelter have ceased operations. But Doctors Without Borders—it goes by the initialism MSF, for the French Médecins Sans Frontières—retains teams at the Sudanese border and has 29 members traveling with the people on foot, each of them carrying a single, bookbag-sized backpack full of medical supplies. "Our teams on the ground are constantly rethinking the way they do things," says Ana Santos, an industrial designer who heads MSF's Displacement Unit in Nairobi. "If it wasn't for this bag, the people would be away from care for a week."

So... what's in the bag? It's a pared-down, lightweight set of solutions to worst-case problems—portable triage. And its contents reflect just how awful things are on the road from Kodok to the border.

Inside the MSF Grab-Bag

Portable malaria test kit

Thermometer

Antimalarial drugs

Acetaminophen (for pain, fever, and inflammation)

Oral Rehydration Solution (basically salts and sugar to treat severe dehydration)

Antibiotics

Solar charger (for areas where cellular communication might be possible)

Wound dressing materials (a small scissors and self-adhering bandages)

Suture kit

Sterile water

Antiseptic wipes

Water purification tablets

The meds tell the tale—malaria is a threat, as are cholera and respiratory illness. "Because of the crowding that's happening, there are contagious cases, and lots of violence," Santos says. "The teams are able to perform lifesaving operations with simple dressings."

But why water purification tablets instead of something more sophisticated, like a Lifestraw, or something with activated charcoal or ultraviolet light? The main source of water for displaced people in South Sudan is the White Nile, which practically gives you diarrhea just looking at it. "We weren't able to identify off-the-shelf products to filter water," Santos says. "The water we're looking at is very contaminated with a variety of problems. We're talking about harsh conditions."

It takes about five days for a healthy person to walk from Kodok to the refugee camp at the border with Sudan—much longer for the elderly, the sick, and children. The idea is that MSF teams will eventually be able to connect with the grab-bag teams to resupply along the way. Until then, they're out of contact. "We have a mission at the border, so we contacted them to find out if they're receiving any news or seeing our people," Santos says.

For the next iterations of the bag, she says she'd love to have better water purification and communications solutions. Meanwhile, new problems are on the horizon: The rainy season starts in four weeks, and the whole region turns to mud.