World Health Organization (WHO) officials said at a briefing on Monday 20 July that more than 80% of new Bundibugyo Ebola cases in DR Congo now arise outside any known contact chain 1. Bundibugyo is a rare Ebola species first identified in Uganda in 2007. A contact chain is the documented trail linking a new case back to a known infected person, and it is the list every containment tool works from. A response that cannot see where its next case is coming from is no longer tracing an epidemic; it is counting one.
The scale arrived with the same briefing. The European Centre for Disease Prevention and Control (ECDC), the EU's infectious disease agency, recorded 2,344 confirmed cases and 930 deaths through 18 July, with 724 patients hospitalised in isolation 2. That puts isolation coverage, the share of confirmed patients held in hospital rather than at large in the Community, near 31%. It stood at 39% a week ago and 44% on 3 July . The US Centers for Disease Control and Prevention (CDC) modelled this outbreak in June at a reproduction number of 2.51, the average number of people each case infects, and named 70% isolation as the point at which transmission collapses . Coverage has moved away from that fork at every reporting point since.
Tedros Adhanom Ghebreyesus, WHO's Director-General, called this the third-largest Ebola outbreak on record and drew the comparison himself: the 2018-20 Kivu epidemic in eastern DRC took more than ten months to reach 2,000 confirmed cases, and this one took two 3. A single day, 17 to 18 July, added 83 confirmed cases and 40 deaths 4.
The calmer reading of that falling percentage deserves a hearing. There are 724 people in isolation now, more than at any earlier point, and a percentage can fall while absolute capacity rises if case-finding improves and the denominator grows faster than the wards. Lethality supports the calm view too: WHO's DON613 bulletin of 17 July gives a case-fatality ratio of 39%, sitting between the 30% recorded in Uganda's 2007 Bundibugyo outbreak and the 50% recorded in DRC in 2012 5. Set against the only two prior outbreaks of this species, 39% is what Bundibugyo has always done. The 80% figure is what defeats the benign reading. Better case-finding pushes cases into known contact lists; it does not push them out.
