What was 'Disease X' and what can we learn from it?

In early December, international alarm bells went off because of a mysterious disease circulating in a remote part of the Democratic Republic of Congo. The Africa Centers for Disease Control and Prevention dubbed it "Disease X."

National and international health experts raced to the scene. But because the rainy season made dirt roads hard to pass, it took days to get from the capital Kinshasa to villages in the Panzi district in Kwango Province, located in the south of the vast country. It was in these far-flung villages that about 900 people had fallen ill between late October and mid-December with symptoms ranging from fever to body weakness to difficulty breathing. Forty-eight of them died. And many of the ill are young children. At the very end of November, local medical providers alerted national authorities that they weren't sure what was causing all these people to fall sick.

Once the medical experts arrived, they quickly gathered samples from the sick to take back to the provincial capital of Kenge and the national capital of Kinshasa so diagnostic tests could be run. But because of the arduous journey, when the first samples arrived "the blood and serum were poorly preserved," said Dr. Jean Kaseya, the director general of Africa CDC. "There was no way for them to conduct the testing."