The head of the World Health Organization said Wednesday there was little risk of the Ebola outbreak in central Africa developing into a pandemic, even as the number of suspected cases and deaths continued to rise.

The outbreak is “not a pandemic emergency,” Tedros Adhanom Ghebreyesus, the WHO’s director-general, said at a news conference in Geneva. He said the agency had assessed the risk as “high at the national and regional levels, and low at the global level.”

By Wednesday, five days after the outbreak was declared, the number of suspected infections had risen to nearly 600, including 139 deaths, Tedros said. He said the outbreak was concentrated in two provinces of Congo, Ituri and North Kivu, including their respective capitals. Neighboring Uganda has also reported two cases in travelers from Congo, one of whom has died, he said.

“We expect those numbers to keep increasing, given the amount of time the virus was circulating before the outbreak was detected,” Tedros said.

Health officials are still trying to pinpoint the start of the outbreak, but they believe it started “a couple of months ago,” Anais Legand, a WHO technical officer, said at the news conference. Officials have said that the outbreak could last for months and that many infections may have gone unreported.

Tedros defended the agency’s response to the outbreak Wednesday, after Marco Rubio, the U.S. secretary of state, said Tuesday the WHO had been “a little late to identify this thing unfortunately.”

Asked about the comments, Tedros said they may have reflected a “lack of understanding” about how the WHO functions. “We don’t replace the country’s work, we only support them,” he said, referring to health authorities in countries where an outbreak begins.

The United States formally withdrew from the WHO in January. That deprived it of its biggest funding source and forced it to cut its 2026-27 budget by $500 million.

Asked Wednesday whether the public health response had been hampered by U.S. funding cuts, Tedros said that given the complexity of the circumstances surrounding the outbreak, “it would be very difficult to associate it with funding alone.”

Ituri, a province in Congo’s northeast, where the outbreak is centered, is a challenging place to monitor and control the spread of an outbreak. Large numbers of people have been displaced by years of conflict.

Local officials have also said that equipment in the province could only test for the most common species of Ebola, known as Zaire, not the relatively rare species, known as Bundibugyo, which is responsible for the current outbreak. Because of that, early results returned negative readings. Diagnostic kits capable of identifying Bundibugyo were flown in over the weekend, a WHO representative said.