'If the cholera spreads, the refugee camps will become burial grounds, cemeteries. We're in charge of health at the camps and it's mind-bending,' said Jean-Francois Alesandrini, an MSF spokesman, yesterday.
Even by the exacting standards of the world's biggest private medical relief group, the Rwanda disaster is worse than anything the doctors have seen - including Kurdistan and Somalia.
MSF has more than 300 volunteers in Rwanda and at refugee camps in neighbouring Zaire and Tanzania - the biggest mobilisation since its creation in 1971. Another 160 are due to be despatched this week.
MSF was set up in Paris by doctors who had played a part in the 1968 student and workers' uprising. Full of ideals but disillusioned by politics, they wanted to do something practical for humanity. Today it has an annual budget of 1bn francs ( pounds 115m).
Increasingly, MSF doctors are ignoring diplomatic niceties and speaking out against what they see as human disasters rather than biting their tongues and treating the dying in silence.
In an interview with the weekly Nouvel Observateur, Rony Brauman, a former MSF chief, last week accused the rump Hutu government of organising the refugee exodus in an attempt to form a power base outside Rwanda.