Congo’s Ebola outbreak passes 11,000 cases, and the strain driving it has no vaccine

Ebola has now infected more than 11,000 people in the Democratic Republic of Congo, according to government figures released on Tuesday, and at least 5,387 of them have died.

The count, 11,042 confirmed cases, puts the outbreak behind only the West African epidemic of 2014 to 2016 in the history of the disease. What makes this one harder is the virus itself. It is the Bundibugyo strain, one of the rarer forms of Ebola, and no vaccine or treatment has been developed specifically for it. It kills roughly half of the people it infects.

Why is it spreading so fast?

Late detection, armed conflict and overstretched health services have all let the virus move faster than in Congo’s earlier outbreaks. Cases have been confirmed in eight of the country’s 26 provinces, and many people are dying at home or in their communities rather than in treatment centres, which makes it harder to find the people they were in contact with.

The east of the country, the centre of the outbreak, is also one of its most violent regions. Armed men killed at least 33 people in a village in the Ebola-hit east last week, the kind of attack that drives families from their homes and health workers out of the areas they are trying to reach.

The figures are confirmed cases only. Suspected or probable cases that were never tested are not in the official count, so the true toll is likely to be higher.

Why does the strain matter so much?

Congo has beaten large Ebola outbreaks before, most recently with the help of vaccines that are highly effective against the Zaire strain, the most common form. Those vaccines were built for Zaire, not for Bundibugyo, so health workers are fighting this outbreak largely with the older tools: finding cases, isolating patients, tracing contacts and making burials safe.

The World Health Organization approved clinical trials of two new Ebola vaccines earlier this month. It expects results in early 2027, which means any vaccine is months away even if the trials succeed.

How big is it compared with past outbreaks?

The deadliest Ebola epidemic on record, in Guinea, Liberia and Sierra Leone from 2014 to 2016, infected more than 28,600 people and killed more than 11,000. Congo’s outbreak has already passed the halfway mark on both counts. Cases linked to it have now been reported in East, Central and West Africa, the widest spread of any Ebola outbreak on the continent.

At the death rate this strain carries, every thousand new infections means hundreds more deaths, a large share of them among the families and health workers who care for the sick.

What does it mean beyond Africa?

Ebola spreads through direct contact with the bodily fluids of a sick person or someone who has died of it, not through the air, and outbreaks have rarely spread far beyond the regions where they start. The risk to travellers and to countries like Australia remains low. But an outbreak this large, in a region with heavy cross-border movement, raises the chance of cases turning up in new countries, and it puts the cost of containing it onto some of the world’s poorest health systems.

During the West African epidemic, Australia suspended visas for travellers from the affected countries in October 2014, one of several governments to tighten their borders as case numbers climbed.