United Nations workers in Mbandaka, Democratic Republic of the Congo, prepare to distribute medical supplies to help tackle an Ebola outbreak in May.Credit: Junior D. Kannah/AFP/Getty

An outbreak of the Ebola virus that began in the Democratic Republic of the Congo (DRC) in early May has been declared over by the country’s health ministry.

A total of 53 people were infected, 29 of whom died. Forty-two days have now passed since the last person known to be infected was deemed free of the disease — the standard for declaring a country Ebola-free, and twice the maximum incubation period for the disease.

The outbreak was centred in remote rural regions of the northwestern Équateur Province, but cases were also reported in mid-May in Mbandaka, a city with a population of more than one million people that sits on the banks of the Congo River, a major transport route. That prompted fears that the disease could spread quickly both in the city and to other regions — as happened in the large 2014–16 Ebola epidemic in West Africa.

Learning from mistakes in that outbreak, the World Health Organization and other public-health bodies quickly gave the DRC support — including helping to deploy, for the first time early in an outbreak, several thousands of doses of an experimental Ebola vaccine. Health agencies used a ‘ring vaccination’ strategy: they immunized contacts of infected people, and their contacts, as well as front-line responders. Data from the deployment of the vaccine, which is made by Merck, are being analysed for insights into its efficacy.

The outbreak is the DRC’s ninth since the first ever known outbreak of Ebola virus occurred in the nation in 1976. The country has since become experienced at swiftly implementing the public-health measures needed to contain the virus’s spread, such as identifying new infections, monitoring and isolating people with whom infected people have had contact, and carrying out safe burials. Previous Ebola outbreaks in the DRC have also been contained in a matter of months.