World health officials are warning of a deadly, previously unknown disease rapidly spreading in the Democratic Republic of Congo’s northwest that’s killed nearly half of its victims in one locale within hours of the first symptoms developing.

As of Feb. 15, a total of 431 cases resulting in 53 deaths have been reported, with those illnesses emerging only weeks after the disease’s first detection last month in Équateur Province, the World Health Organization’s Regional Office for Africa said in a public bulletin shared last week.

“The outbreak, which has seen cases rise rapidly within days, poses a significant public health threat,” the WHO’s regional office said.

The disease, first reported among children linked to a dead bat, progresses rapidly “with nearly half of the deaths occurring within 48 hours of symptom onset in one of the affected health zones, and an exceptionally high case fatality rate in another,” health officials said.

Health officials said they’ve ruled out other hemorrhagic fever diseases like Ebola and Marburg as causing the illnesses. These are two highly fatal diseases among humans that are believed to spread to people through fruit bats.

Though the overall case fatality rate is 12.3%, the rate is 66.7% in one of two outbreak areas, where eight of the 12 cases have resulted in death.

The disease’s emergence follows three children, all under the age of 5, dying between Jan. 10 and 13 after developing a fever, headache, diarrhea and fatigue. These symptoms, reported in the same village around Bolomba, then turned into hemorrhaging.

“Reports indicate that the children had consumed a bat carcass prior to onset of signs and symptom,” health officials said.

Shortly after those illnesses emerged, four additional children in the same village, between the ages of 5 and 18, came down with similar symptoms. Hundreds of similar cases since then have been reported in the region of Basankusu, which is roughly 115 miles northeast of Bolomba.

“The exact circumstances of exposure have not yet been established in both outbreaks. Additionally, no epidemiological links have been established between the cases in the two affected health zones,” officials said.

“Urgent action is needed to accelerate laboratory investigations, improve case management and isolation capacities, and strengthen surveillance and risk communication. The remote location and weak healthcare infrastructure increase the risk of further spread, requiring immediate high-level intervention to contain the outbreak.”

The disease’s initial, observable symptoms include fever, chills, headache, muscle pain or soreness, body aches, sweating, a runny nose, neck stiffness, cough, vomiting, diarrhea and abdominal cramps.

Michael Head, a senior research fellow in global health at the University of Southampton in Britain, told The Washington Post that outbreaks of mysterious illnesses “will happen many times around the world” and that while it’s possible it can turn into something monumental like COVID-19, he said that it “is very rare.”

“Usually, it’s a bug … that we know about but haven’t yet diagnosed in that particular outbreak,” Head said.

The cases come amid a separate warning of a potential new pandemic emerging from the DRC’s eastern region in part due to the U.S.’s recent freeze of humanitarian aid under President Donald Trump’s administration.

Dr. Jean Kaseya, who serves as the director general of the Africa Centres for Disease Control and Prevention, recently told news outlet Health Policy Watch that laboratory testing has all but stopped in the area and there’s limited transmission of medical information.

The DRC’s eastern region, particularly around Goma and Bukavu, could consequently become a hotspot for disease transmission due to this aid freeze as well as an ongoing rebel conflict in the region, Kaseya said.

The region’s invasion of Rwandan-backed M23 rebels has resulted in medical facilities becoming overwhelmed and over a million people being displaced, including hundreds of people who were receiving treatment at health facilities for mpox. There also are outbreaks of cholera and measles in the area, he said in a public briefing Thursday.

“This can be the entry point for a new pandemic,” Kaseya told Health Policy Watch. “The combination of insecurity, lack of funding and lack of medical countermeasures, [means] we are playing with fire.”

The Trump administration last month cut off approximately $60 billion in annual aid and development programs through the U.S. Agency for International Development and the State Department. A federal judge on Tuesday ruled that the funding must immediately resume, however, after a temporary restraining order against the funding freeze was ignored by the Trump administration.