CAPE TOWN, South Africa, Feb. 18 -- At least 61 miners in eastern Congo have died and hundreds have become ill from what appears to be the largest outbreak in 80 years of a highly virulent, airborne version of plague, international health officials reported Friday.
The officials said thousands more workers had fled an 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-based 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.
Officials said the outbreak in Congo was the deadliest since the 1920s, when pneumonic plague killed about 9,300 people in Manchuria.
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 contain it quickly. The first cases apparently occurred in December, in the days after the mine opened following a period of disuse. Because the nearest health facilities were primary-care centers several miles away, each with only a few beds, it took two nearly two months for officials to identify plague as the likely cause of the 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 WHO plague specialist who took part in a conference call with reporters Friday when the outbreak was announced. "If we can find the cases and treat them, effectively this can be solved."
The mine, in the remote town of Zobia, had drawn 7,000 workers from throughout the region. An estimated 400 are believed to be sick, and most of the other miners have fled, health officials said. They said Congolese soldiers, who apparently control the mine, remain at the site.
The region has been troubled by years of warfare, fueled in part by the struggle for control of its rich natural resources, including diamonds. The conflict ended officially with a peace deal in 2002, but violence and instability remain common throughout eastern Congo, limiting access by humanitarian groups.
The years of war have left the area among the world's poorest and least healthy, with unusually 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 is to fly to the region on Monday. Teams from Medair and Doctors Without Borders are already in the area. Emergency stocks of antibiotics and other medicines have been flown in as well. Most of eastern Congo is reachable only by air because of the poor condition of the road system, which has not been maintained since the Belgian colonial regime ended in 1960.
A series of tests for pneumonic plague have proved inconclusive, with two positive tests out of 22 performed on miners. But health officials expressed a high degree of certainty, based on the reported symptoms and course of the disease, that they were dealing with an outbreak of pneumonic plague. They questioned the reliability of the tests, which they said were new and might miss some variations of the disease.
"We think very strongly it is plague," said Alena Koscalova, a Doctors Without Borders medical official who oversees the region where the outbreak has occurred.
Speaking by phone from her office in neighboring Uganda, Koscalova 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," she said.