CAPE TOWN, South Africa, Feb. 18 -- International health officials warned on Friday that 61 miners in eastern Congo have died and hundreds have become ill from what appears to be the largest outbreak in several decades of a highly virulent, airborne version of plague.
Health officials said thousands more workers have fled the open-pit diamond mine that is the epicenter of the outbreak, possibly spreading the disease deep into a rural province with few health facilities.
"It can pop up in many places now," said Marian van der Snoek, a medical official with the Swiss aid group Medair, who spoke by telephone from her office in Bunia, in Congo's northeastern corner. "We don't know where these people have fled."
The World Health Organization, the Congolese government and several aid agencies are seeking to determine the extent of the epidemic and to train medical workers in the region to spot the disease, which attacks the lungs and is spread mainly by coughing. Left untreated, the disease kills the overwhelming majority of its victims.
Pneumonic plague is both rarer and more frequently fatal than bubonic plague, which is spread by the bites of rat-borne fleas. Bubonic plague became notorious for causing millions of deaths in Europe in devastating medieval epidemics. Antibiotics and other modern medicines have made both forms of the disease uncommon in the developed world, but plague is endemic throughout much of Africa and the developing world. In eastern Congo alone, there are typically 1,000 cases in a year. Only 2 percent of the worldwide cases of plague each year are pneumonic.
What especially alarmed health officials about the outbreak at the diamond mine was their inability to rapidly contain it. The first cases have been traced to December, in the days after the mine opened after a period of disuse. The nearest health facilities are primary-care health centers several miles away, each with only a few beds.
It took nearly two months for plague to be identified as the likely cause of the series of deadly lung infections among the miners. By then, most of those exposed to the disease had left the area.
"It's very important to isolate, quarantine people," said May Chu, a World Health Organization plague specialist who was part of a conference call with reporters announcing the outbreak. "If we can find the cases and treat them effectively, this can be solved."
The mine, in the remote town of Zobia, had 7,000 workers from throughout the region. An estimated 400 are sick, and most of the other miners have fled, health officials said. They said Congolese soldiers, who apparently control the mine, remain there.
The region has been the scene of years of warfare, fueled in part by the struggle for control of rich natural resources such as diamonds. The war ended officially with a peace deal in 2002, but violence and instability remain common throughout eastern Congo, limiting the access of humanitarian groups.
Years of war have left the area among the world's poorest and least healthy, with uncommonly high rates of child mortality and frequent deaths from diseases that are preventable and treatable in places with more advanced health systems.
A group of 10 WHO officials are to fly to the region on Monday. Teams from Medair and Doctors Without Borders already are there. Emergency stocks of antibiotics and other medicines have been flown in as well. Most areas of eastern Congo are reachable only by plane because of decades of deterioration of the road system, left without maintenance since the Belgian colonialists left in 1960.
A series of tests for pneumonic plague have proven inconclusive, with two positive tests out of 22. But health officials expressed a high degree of confidence, based on the reported symptoms and course of the disease, that the outbreak is caused by pneumonic plague. They questioned the reliability of the tests, which are new and may miss some variations of the disease.
"We think very strongly it is plague," Alena Koscalova, a Doctors Without Borders medical official who oversees the region of the outbreak. She spoke by phone from her office in neighboring Uganda.
She said the progress of the disease would depend on the ability of health officials to track its path and treat its victims in the next few weeks.
"It depends very much on the actions we are going to take," Koscalova said.