Congo's Ebola outbreak passes 10,000 cases as vaccine trial begins

The Ebola outbreak in the Democratic Republic of Congo has passed 10,000 confirmed cases, making it the largest outbreak of the Bundibugyo strain ever recorded and the second-largest Ebola epidemic of any kind.

As of October 29, Congo had reported 10,274 confirmed cases, including 4,992 deaths, based on data up to October 28, according to the European Centre for Disease Prevention and Control (ECDC). Community transmission is continuing.

A strain without a vaccine

Ebola disease is caused by several related viruses. The vaccines and treatments developed after the 2014-16 West Africa epidemic, which infected more than 28,000 people, target the Zaire strain. There is no approved vaccine or specific treatment for Bundibugyo, which makes this outbreak much harder to contain.

Congo declared its 17th Ebola outbreak in May, and the World Health Organization declared it a public health emergency of international concern on May 16.

The vaccine trial

On October 23, the WHO announced the first vaccinations in a clinical trial called Tumaini, which means "hope" in Swahili, in Bunia, in Congo's north-eastern Ituri province.

The first participants received Ervebo, the vaccine licensed for the Zaire strain, to test whether it offers any cross-protection against Bundibugyo. Two vaccine candidates designed specifically for Bundibugyo, now in earlier, smaller trials, are due to be added.

The trial uses ring vaccination, in which the contacts of confirmed cases, and their contacts, are vaccinated to build a protective "ring" around each case. It is co-led by Congo's National Institute for Biomedical Research and the University of Antwerp in Belgium. A separate study, BRAVO, is testing Ervebo in about 20,000 frontline workers.

It is not yet known whether Ervebo will protect against Bundibugyo.

Beyond Congo

The outbreak has reached other countries. Nigeria reported its first case on October 20, and the patient was later evacuated to Switzerland for treatment, according to reports. In Kenya, 20 contacts of a suspected case were released from quarantine, the UN said.

The US Centers for Disease Control and Prevention said on October 30 that no cases linked to the outbreak have been confirmed in the United States and that the risk to the American public remains low.

What comes next

Health workers face the usual obstacles of Ebola response, including tracing contacts, safe burials and building community trust, in a region also affected by armed conflict. If the trial shows that a vaccine works, it could change the course of this outbreak and future ones.