Congo's runaway Ebola outbreak has broken out of its eastern stronghold for the first time, reaching Sud-Ubangi province in the west after a patient who had crisscrossed the country by road, river and border crossing died there, provincial authorities said Friday.

Acting Governor Jean-René Galekwa Vundawe said the confirmed case makes Sud-Ubangi the seventh province hit by the outbreak, and the first in western Congo — a troubling geographic leap for a virus that had largely stayed confined to the country's east. According to Al Jazeera, the patient developed symptoms in Kisangani after traveling through Rwanda, Uganda and Ituri province, then continued by boat down the Congo River to Lisala before being transferred to a hospital in Gbaka, where he died. Thirty-eight contacts have since been placed under quarantine.

"The route taken both by the patient and by the boat exposes the populations" of the provinces he passed through, Galekwa said, according to Al Jazeera's report.

An Outbreak Already Off the Charts

As of September 9, Congo's health ministry had confirmed 6,942 cases and 3,349 deaths in this outbreak alone — a fatality rate of roughly 48%, among the highest ever recorded for an Ebola event, per the World Health Organization. First declared in May, it is caused by the rarer Bundibugyo strain of the virus, for which there is no approved vaccine or treatment, and it has already been labeled the largest Ebola outbreak in Congo's history and the fastest-growing on record. The WHO has said the epidemic remains out of control and is on pace to surpass the 2014-2016 West Africa outbreak — history's deadliest, with more than 11,000 deaths — if the current trajectory holds.

THE OUTBREAK IS SPREADING UNDER EXTREMELY DIFFICULT CONDITIONS, FUELED BY INSECURITY, DISPLACEMENT, A HEALTH WORKERS' STRIKE AND INTENSE POPULATION MOVEMENTS.

Aid groups on the ground describe an overwhelmed system. Doctors Without Borders (MSF) says it has deployed more than 1,700 staff across nine treatment centers in five provinces, with over 480 beds, and has admitted more than 2,770 patients since May. Armed conflict, mass displacement and a strike by health workers in parts of the affected region have all hampered the response, complicating contact tracing precisely as the virus finds new routes to travel.

What's Next

Health authorities are now racing to trace everyone who had contact with the deceased patient along his journey through four provinces before symptoms fully emerged, while monitoring Sud-Ubangi's border areas with the Central African Republic and Republic of Congo for further spread. With no licensed vaccine for the Bundibugyo strain and case numbers still climbing week over week, the WHO and Congolese officials say containment now hinges on interrupting the long-distance travel patterns — river transport especially — that let the virus leap hundreds of miles beyond its original epicenter.