Three Red Cross volunteers have died, believed to have contracted the Ebola virus during a humanitarian mission in the Democratic Republic of the Congo in March, the organization said.

“At the time of the intervention, the community was not aware of the Ebola Virus Disease outbreak, and the outbreak had not yet been identified. They are among the first known victims of the outbreak,” the International Federation of Red Cross and Red Crescent Societies (IFRC) said Saturday.

The volunteers were identified as Alikana Udumusi Augustin, Sezabo Katanabo and Ajiko Chandiru Viviane.

Vivaine died on May 5, Katanabo on May 15 and Augustin on May 16.

They are believed to have contracted the virus while “carrying out dead body management activities” on March 27 during a mission unrelated to Ebola, the IFRC said.

They were volunteers from Congo’s Red Cross society, serving in the Mongbwalu branch of the Djugu territory in Ituri province — the epicenter of the outbreak.

“We extend our heartfelt condolences to their families, loved ones, fellow volunteers and colleagues,” the organization said. “These volunteers lost their lives while serving their communities with courage and humanity.”

Virus spreads to Uganda

The World Health Organization declared the outbreak, which first emerged in Congo and has spread into Uganda, a public health emergency of international concern on May 17.

As of Thursday, there were 746 suspected cases of the virus and 176 deaths among suspected cases reported in Congo, the World Health Organization said.

Thus far, there have been at least 88 confirmed cases, with 10 deaths among those cases, including one in Uganda, according to the WHO.

Among the confirmed cases is an American surgeon who contracted the virus while working in Congo. He was taken to Germany earlier this week for treatment.

As of Thursday, the WHO said, there were two cases in Uganda. On Sunday, Uganda’s Ministry of Health said the number of cases there had risen to five.

The three new cases in Uganda include a Ugandan driver who transported the country’s first confirmed case, a Ugandan health worker exposed to the virus while taking care of the country’s first confirmed case, and a Congolese woman who entered Uganda with mild abdominal symptoms.

All are receiving treatment.

‘Worrisome’ outbreak

WHO Director-General Tedros Adhanom Ghebreyesus on Friday called the outbreak in Congo “deeply worrisome.”

“These numbers are changing as surveillance efforts and laboratory testing is improving, but violence and insecurity are impeding the response,” he said.

Since the outbreak, aid and personnel have been sent to Congo from regional and international partners including the WHO, the U.S. Centers for Disease Control and Prevention, the European Center for Disease Prevention and Control, Doctors Without Borders and the U.S. State Department, which said it mobilized $23 million in foreign assistance.

The outbreak is being driven by a strain of Ebola called Bundibugyo, which causes hemorrhagic fever and has no approved vaccines or treatments.

The CDC on May 18 issued an order barring entry to foreign nationals who were in Congo, Uganda or South Sudan within 21 days of their arrival to the U.S.

U.S. citizens and permanent residents who were in these countries within 21 days are permitted to enter, but must enter at Washington-Dulles International Airport or Hartsfield-Jackson Atlanta International Airport for enhanced public health screening.

To date, there have been no suspected or confirmed cases of Ebola from the current outbreak reported in the U.S., the CDC said.