Doses of the most promising potential vaccine against the Bundibugyo virus driving the Ebola outbreak in central Africa will not be available for six to nine months, the World Health Organization has said, as the number of suspected cases climbed to nearly 600.
Dr Tedros Adhanom Ghebreyesus, the WHO director-general, told a press briefing on Wednesday that there had been 139 suspected deaths from the outbreak, which has spread across the Democratic Republic of the Congo and into Uganda. The WHO declared the outbreak a Public Health Emergency of International Concern (PHEIC) on May 18, its highest global alert level, after laboratory analysis confirmed the Bundibugyo ebolavirus in eight of 13 blood samples collected from Ituri province.
Dr Vasee Moorthy, who leads the WHO’s research and development blueprint, said the candidate vaccine uses the same basis as existing Ebola vaccines targeting the Zaire strain, but no doses are currently available for clinical trials. “The information that we have is this is likely to take six to nine months,” he said.
An alternative vaccine, developed on the same Oxford University platform used for AstraZeneca’s Covid-19 jabs, could be available for clinical trials in two to three months, Dr Moorthy said, but there is “a lot of uncertainty” because data from animal efficacy tests are not yet available. Scientists at the University of Oxford are also working on multivalent vaccines that could protect against multiple filoviruses, including Bundibugyo, using platforms such as ChAdOx and mRNA, but no licensed vaccine or specific treatment currently exists for the disease.
The outbreak is believed to have begun spreading “a couple of months ago”, according to WHO officials, who said a “super-spreader event” – possibly a funeral – in early May accelerated transmission. The WHO was first alerted by Congolese authorities in early May to a high-mortality outbreak of an unknown illness in Ituri province, and an investigation team dispatched on May 12 collected samples that confirmed Bundibugyo virus disease three days later. The DRC’s health ministry officially declared the country’s 17th Ebola outbreak on May 15, and Uganda confirmed its first imported case the following day. An American doctor working in the DRC also tested positive for the virus.
As of the latest figures, there are 34 confirmed cases and 134 confirmed deaths, with nearly 600 suspected cases and 139 suspected deaths overall. The primary epicentre remains Ituri province in northeastern DRC, where more than 100,000 people have been displaced by armed conflict, and cases have also been detected in Goma, North Kivu province. Uganda has reported two confirmed cases and one death linked to travel from the DRC. Rwanda closed its land border with the DRC in response, and the US Centers for Disease Control and Prevention issued a Level 3 Travel Health Notice for the DRC and a Level 1 notice for Uganda. The WHO assesses the risk as high at the national and regional levels and low globally, while modelling from Imperial College London suggests the true number of cases could already exceed 1,000.
The challenge of diagnosis and security
The response effort is being severely hampered by a combination of endemic diseases and a volatile security situation, making it extremely difficult to identify and contain the virus. Dr Tedros said the security situation in Ituri, where armed conflict has displaced more than 100,000 people in recent months, had “complicated detection efforts”. Health facilities cannot provide care or carry out surveillance if health workers are fleeing, he warned, and access issues such as frequently cancelled flights are making it difficult to deliver tests and supplies to the remote, war-torn area.
Compounding the problem, other illnesses endemic to the region, such as malaria and typhoid, share the same early symptoms as Ebola – fever, headache and muscle pain. This similarity can delay diagnosis, as patients may be treated for those diseases before Ebola is considered. The rarity of the Bundibugyo strain also makes detection through testing more difficult. Later symptoms of the virus include vomiting, diarrhoea and bleeding; the incubation period is 2 to 21 days, and infected individuals are typically not infectious until symptoms appear. The virus spreads through direct contact with blood or body fluids of an infected person or contaminated objects, not through the air. Previous Bundibugyo outbreaks have had case fatality rates between 25% and 50%, comparable to the Zaire strain. The virus was first identified in 2007 in western Uganda.
Officials said identifying all existing chains of transmission is the absolute priority. “That will then enable us to really define the scale of the outbreak and be able to provide care,” said Dr Chikwe Ihekweazu, the WHO emergencies lead.
WHO defends its response to criticism
The WHO has pushed back against criticism from US Secretary of State Marco Rubio, who said the organisation had declared the outbreak “a little late”. Dr Tedros said such remarks were probably based on “a lack of understanding” of how the International Health Regulations (IHR) work. “We don’t replace the country’s work, we only support them,” he said. A senior State Department official had suggested it took the WHO ten days to confirm the outbreak, implying a faster response could have been possible. The WHO maintained that initial detection falls under national health authorities and that it provided support as soon as it was aware.
The Trump administration withdrew the United States from the WHO earlier this year, a move criticised by some as weakening global health security and pandemic preparedness. The withdrawal has reduced WHO funding and led to the recall of US personnel. Despite this, the US has committed approximately $13 million in assistance and aims to open about 50 clinics in the DRC. The US has also implemented enhanced travel screening and entry restrictions to prevent the virus from entering the country.