Health authorities say a new Ebola outbreak has been identified in the Democratic Republic of the Congo, with more than 300 suspected cases and at least 88 deaths reported. Cases have also been reported in neighboring Uganda, where officials are monitoring people for symptoms as the outbreak response ramps up. On Sunday, the World Health Organization declared the event a public health emergency of international concern, signaling the crisis’s cross-border risk and the need for coordinated international action.
Ebola is caused by several different viruses, and the WHO says three are known to cause large outbreaks: Ebola virus, Sudan virus and Bundibugyo virus. According to the WHO, the current Congo outbreak is caused by the Bundibugyo virus, which the agency describes as rare and responsible for only two previously reported outbreaks. That detail matters for preparedness because different Ebola strains and outbreak settings can shape how quickly cases grow and how public-health teams manage detection and treatment.
The World Health Organization says fruit bats are believed to be the natural hosts for Ebola viruses. The WHO also says other animals, including apes and monkeys, can become infected. People can be infected through contact with infected animals, and Ebola can then spread from person to person through contact with the bodily fluids of infected people, such as blood, feces or vomit, or through surfaces contaminated by those fluids.
Health authorities and experts emphasize that Ebola’s incubation period can vary. The U.S. Centers for Disease Control and Prevention says symptoms can appear from two days to three weeks after exposure, though they usually emerge within about a week. The CDC describes illnesses that often begin with flu-like symptoms, including fever, aches, fatigue and sore throat, before patients can develop gastrointestinal problems, rashes, seizures and bleeding.
The WHO says Ebola has an average fatality rate of around 50%, though rates vary from 25% to 90% in previous outbreaks. The availability of medical tools can be limited by which Ebola virus is causing the outbreak. The WHO says there are approved vaccines and treatments only for Ebola virus, not for the Bundibugyo virus.
The WHO and CDC notes also place the current outbreak in a longer pattern of epidemics concentrated in sub-Saharan Africa, where the viruses that cause Ebola are native. The most severe outbreak on record began in 2013 and spread across Guinea, Liberia and Sierra Leone, with more than 28,000 cases and more than 11,000 deaths, and later cases tied to travelers and health workers in the United States, the U.K., Italy and Spain. Researchers have said that outbreak linked to the Ebola virus type may have started in southeastern Guinea after a child—described as a “patient zero”—came into contact with infected fruit bats.
A second major outbreak occurred in 2018, when Ebola spread through Congo’s North Kivu, South Kivu and Ituri provinces, with some cases also reported in Uganda. The CDC says that outbreak had more than 3,400 reported cases and more than 2,200 deaths, with a fatality rate of 66%, and it was caused by the Ebola virus. This new Congo outbreak, announced with cases also reported in Uganda, is also described as being in Ituri, on the border with Uganda.
Bundibugyo strain outbreaks are part of that history as well. The CDC says that an outbreak in 2007 in western Uganda, on the border with Congo, was the first reported occurrence of the Bundibugyo strain, with 131 reported cases and 42 deaths. The CDC said that the fatality rate for the Bundibugyo strain appeared to be lower than for the other strains, and it also noted that there is still no specific treatment or vaccine for the Bundibugyo virus.
Ebola was first identified in 1976 after two outbreaks broke out in quick succession in what was then Sudan and what is now South Sudan and Congo. Scientists believe the initial outbreak began in a cotton factory where workers had contact with bats in warehouses, though the source was not confirmed. Studies later cited by the WHO say at least 151 people died and 284 cases were reported, including deaths after sick people were taken to hospitals and spread the disease to health workers and others while it was still not known.
Months later, an outbreak occurred in northern Congo, then called Zaire, where scientists say it first led to identification of the Ebola virus. That outbreak began in a remote village near the Ebola River, which the disease was named after. The same year, the WHO says, a British laboratory technician experienced the first known Ebola infection outside Africa after accidentally pricking himself with a needle while studying samples, and he recovered. The WHO says very few Ebola cases have been recorded outside Africa since the virus was identified.