Disease X and other unknowns

On February 26, 2003, Carlo Urbani, an infectious diseases specialist in the World Health Organization's (WHO's) country office in Vietnam, was called to the French Hospital in Hanoi to examine a grievously ill Chinese-American businessman. Johnny Chen had been admitted with severe breathing difficulties shortly after stepping off a flight from Hong Kong and was being nursed in intensive care, where x-rays revealed ominous shadows on his lungs.