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About the time the epidemic was beginning to spread, Khartoum banned relief flights into the south, and most international organizations, including the U.N., stayed out. Medecins Sans Frontieres refused to go along. In the summer of 1988, with a team already in Khartoum, MSF clandestinely sent a second one into the south. The team soon began to hear reports of a strange new "killing disease," which its doctors in Khartoum believed to be kala-azar.
By then Seaman was attending classes at the London School of Hygiene and Tropical Medicine. Four years earlier, she had taken a break from her job in Alaska to work with Ethiopian refugees at a camp in Sudan but came to realize that she needed more training in tropical medicine. When MSF was scouting at the school for a doctor to take on kala-azar in Sudan, she signed up immediately.
Before MSF hired her, there had been a debate within the organization about whether a kala-azar epidemic of such massive size could be handled with no hospitals in the area. "We were going to be dealing with thousands of patients at a time, and we didn't know if it would be possible to do this out in the open and under a tree," says Johan Hesselink, who headed MSF-Holland's southern Sudan operations during that period.
When she finally reached Sudan, even Seaman was not sure what she had signed on for. "My legs swelled up to twice their size with mosquito bites," she says, "and I was ready to cut my one-year contract short by 11 months." But she was clearly captivated by the place and stunned by the enormity of the human catastrophe around the town of Duar, the center of the epidemic. "If you witness a tragedy like that, how can you not be moved?" she explains. "Where else in the world could 50% of a population die without anyone knowing?"
The first step was to find out exactly what the disease was doing. The team had set up operations in a village called Ler, which was several days' walk from Duar. Seaman and a handful of Nuer staff members began to scout on foot toward Duar. What they found was chilling. In some villages, cows wandered unattended; the entire human population had died. Many of the survivors looked like walking skeletons. Sick children carried starving babies after their parents had died on the road. The level of infection in blood tests from villagers in the region was so high that one lab questioned its own interpretation of the readings.
With the infection rate increasing, Seaman asked for an entomologist to pin down the vector, or carrier, of the disease and its habitat. MSF sent Canadian Judith Schorscher from her base in Paris. She spent six months using fans to suck insects into traps, where they could be dissected and analyzed.
It soon became apparent that the carrier was the female Phlebotomus orientalis sand fly, which passes the deadly protozoan to humans in an unusual manner (see box). The tiny insect, which cannot fly very high or far, inhabits the vast, red acacia forests, where it bites its victims in order to get protein-rich blood to develop its eggs. When female sand flies bit people driven by war or famine into the forests from areas where kala-azar was already endemic, the flies picked up the disease themselves, ready to be passed on.