It’s impossible to say how many children have already died in Darfur. The Sudanese armed forces have backed ethnic Arab militias in a scorched-earth campaign against rebellious black farmers. The Khartoum government, while denying any ties to the militias, has kept aid workers and journalists from visiting much of the California-size region. Roughly 1 million villagers have been driven from their homes. More than 150,000 are estimated to have fled across the border to the relative safety of neighboring Chad, where photogapher Bruno Stevens spent several weeks recently documenting their suffering.

Refugees on both sides of the border cling to life, huddled in makeshift camps, without decent food, safe water or adequate shelter against the seasonal rains that have just begun. Diseases like cholera, meningitis and now polio pose a threat more imminent than starvation, especially to the most vulnerable groups, the very young and the very old. This week Secretary of State Colin Powell and U.N. Secretary-General Kofi Annan are both making emergency visits to the region. The hope now is to keep a dire situation from getting worse. “If we get relief in, we could lose a third of a million,” said Andrew Natsios, the U.S. Agency for International Development chief, in early June. “If we do not, it could be a million.”