KINSHASA, Congo — An American doctor is among the newly confirmed cases in an outbreak in Congo of a rare variant of the Ebola virus with no approved vaccines or therapeutics, a Congolese official said Monday, as deaths have surpassed 100 in two provinces and details emerged about the government’s delayed response to the outbreak.

Dr. Jean-Jacques Muyembe, medical director of the Congolese National Institute of Bio-Medical Research, told The Associated Press the doctor is among the cases in Bunia, capital of Ituri province.

The World Health Organization on Sunday declared the outbreak a public health emergency of international concern. As of Monday, there were over 300 suspected cases and 118 deaths in Ituri and North Kivu provinces and two deaths in neighboring Uganda.

The Bundibugyo strain spread undetected for at least a few weeks, health experts and aid workers said. Cases have now been confirmed in Bunia, North Kivu’s rebel-held capital of Goma, Mongbwalu, Butembo and Nyakunde.

“Because early tests looked for the wrong strain of Ebola, we got false negatives and lost weeks of response time,” said Matthew M. Kavanagh, director of the Georgetown University Center for Global Health Policy and Politics. “We are playing catch-up against a very dangerous pathogen.”

He criticized the Trump administration’s earlier decision to withdraw from the WHO and make deep cuts in foreign aid. “When you pull billions out of the WHO and dismantle front line USAID programs, you gut the exact surveillance system meant to catch these viruses early,” he said.

Congo’s health minister, Samuel Roger Kamba, said the government was opening three treatment centers. The WHO said it sent a team of experts and supplies.