Foreign mining companies have locked down operations at Guinea-Conkry operations and evacuated international staff as fatalities from suspected cases of Ebola, one of the world’s most lethal contagious diseases, reached 84, according to executives; four new cases since Wednesday has brought the total to 134.

Ebola is particularly gruesome, manifesting in profuse external bleeding before death — and a 90% mortality rate. Accordingly, “everyone is practicing strict hygiene but there has been no real impact on production,” one senior mining executive told Reuters anonymously; other companies, however, have been preventing people from entering or leaving their mines altogether.

The 60-day-old outbreak epicenter lies in southeast Guinea, close to its main iron ore reserves; the country of 10 million is also a top bauxite exporter rich in gold. Overall, the charity Doctors Without Borders has warned Guinea faces an unprecedented epidemic that is testing fragile health systems across West Africa, with a small handful of cases in next-door Liberia and a highly mineralized Sierra Leone.

Officials from Guinea’s Chamber of Mines have not issued a formal statement, but confirmed mining companies are discussing a best response. “People are locking down camps and keeping movements to a minimum,” one was quoted as saying.

Mining companies, however, were more worried over events in the densely populated Conakry than remote interior mining sites, where controls are easier to implement, added the executive quoted by Reuters. So far, U.N. World Health Organization (WHO) officials have reported 12 suspected cases and four deaths in the capital of 2 million.

Brazilian iron ore giant Vale S.A., meanwhile, said its joint venture BSG Resources Ltd. had pulled its six international staff out of Guinea. “The expatriates have been transferred temporarily to their home countries,” the Rio de Janeiro-based company said in a statement, as local employees are on leave pending “more accurate information about risks of the disease.”

A Geneva-based WHO representative said all Conakry cases originated from one man arriving from the central town of Dobala 190 miles away. “Unfortunately,” the spokesman told Reuters, “this person infected family and health care workers when he went to Conakry for medical attention and died.”

Neighboring Senegal has shut down its land borders with Guinea and its 10 million people, as regional countries are taking precautions — including banning sales and consumption of bats, a delicacy and animal species deemed a virus carrier.