Ebola’s Silent Spread in Congo Exposes Surveillance Gaps
A rare Ebola outbreak that may have circulated undetected in northeastern Congo for several weeks is exposing the difficulty of detecting deadly viruses in regions where malaria, typhoid and other fever-causing illnesses are common and health systems are stretched thin.
About 350 suspected cases and 91 deaths have been reported in northeastern Congo, the country’s health minister Roger Kamba said on Sunday, while neighboring Uganda has confirmed two infections, including one death in Kampala.
A separate case was also reported Sunday in Goma, the eastern Congolese city controlled by Rwanda-backed M23 rebels.
“Hospitals are already under pressure,” Kamba told reporters in Bunia, the capital of Ituri province, where the outbreak is believed to have begun in April and hospitalized 59 people. “It’s not a mystical illness,” he said, urging people with symptoms to seek treatment quickly to help slow transmission.
The outbreak is caused by the Bundibugyo strain of Ebola virus. Congo’s presumed first patient, a nurse in Bunia, developed symptoms on April 24, according to Jean Kaseya, director-general of the Africa Centres for Disease Control and Prevention.
The delayed detection has emerged as a central concern for international health authorities because Bundibugyo remains far less studied than the Zaire strain that caused the devastating West African epidemic a decade ago.
No Vaccine
While Zaire Ebola became the focus of intensive vaccine and therapeutic development after the 2013-2016 outbreak killed more than 11,000 people, Bundibugyo has triggered only two previous outbreaks and has no approved vaccine or antibody treatment.
Early symptoms — including fever, weakness, headache, vomiting and diarrhea — can resemble malaria and other common tropical illnesses, making cases harder to identify quickly in overstretched clinics.
The World Health Organization declared the outbreak a public health emergency of international concern Sunday, citing cross-border spread, unexplained deaths, health-care worker infections and uncertainty over the true scale of the epidemic after what officials described as a four-week detection delay.
The declaration is intended to accelerate international funding, coordination and emergency response efforts.
The outbreak met the threshold for its highest level of alarm, WHO said, because Bundibugyo has no approved vaccine or treatment and the virus is spreading in a conflict-affected region with poor infrastructure and high population mobility.
Initial tests for the more common Zaire strain were negative before additional analysis confirmed Bundibugyo on May 14, according to WHO.
Rapid Ebola tests commonly used in the region may not reliably detect Bundibugyo infections, potentially slowing isolation and contact tracing efforts, according to Robert Garry, a virologist at Tulane University who worked during the West African Ebola epidemic.
The apparent delay in recognizing the outbreak was reminiscent of the early stages of the West African epidemic, when transmission spread between villages before health authorities understood the scale of the crisis, he said.
The outbreak underscores the need for Bundibugyo-specific diagnostics across central and eastern Africa to identify infections earlier in patients with mild symptoms, according to Kirsten Spann, associate dean of research in the Faculty of Health at Queensland University of Technology.
Multiple Foes
Congo has faced several outbreaks of unexplained febrile illness in recent years, including clusters initially suspected to involve malaria, influenza or contaminated food and water before laboratory investigations clarified the causes. Such delays can allow dangerous pathogens to spread silently for weeks before health authorities fully understand what they are dealing with.
At least four health-care workers have died in circumstances consistent with viral hemorrhagic fever, according to the European Centre for Disease Prevention and Control, raising concerns that transmission may have been occurring unnoticed inside clinics before Ebola was identified.
Global health experts have also warned that cuts to foreign aid and disease-surveillance programs could weaken outbreak detection capacity in fragile regions.
The true scale of the outbreak remains unclear because many suspected cases and deaths across Ituri and North Kivu provinces are still under investigation, the WHO said.
Photograph: Staff members at CBCA Virunga Hospital prepare rooms intended for possible suspected Ebola cases in Goma, on May 17, 2026; photo credit: Jospin Mwisha/AFP/Getty Images