What Is ‘Disease X’ and Why Is it Raising Alarm?

Dozens of people have died and hundreds have been sickened by a mystery flu-like illness dubbed ‘Disease X’ that was first detected in a remote region of the Democratic Republic of Congo in late October 2024. International health organizations and the Congolese authorities have dispatched teams to investigate, but they’ve yet to establish the cause. Those infected have suffered fever, headaches, coughs, runny noses and body aches. The high fatality rate and number of cases detected over a relatively short period has sparked concern about the emergence of a new pathogen with the potential to spread widely just a few years after Covid-19 forced countries to shut borders and brought economies and societies to a near standstill.

Roughly the size of Western Europe, Congo is one of the world’s least-developed countries and has a rudimentary health system with little diagnostic capacity to serve its population of more than 100 million people. ‘Disease X’ cases have centered around the Panzi health zone in Congo’s southwestern Kwango province, about 700 kilometers (435 miles) from the capital, Kinshasa. It can take about 48 hours to reach by road, with access all the more difficult during the rainy season. The national government was only alerted to the outbreak on Dec. 1.