We conducted a retrospective analysis of all reports in ProMED-mail that were initially classified as undiagnosed diseases during 2007-2018. We identified 371 cases reported in ProMED-mail; 34% were later diagnosed. ProMED-mail could be used to supplement other undiagnosed disease surveillance systems worldwide.
Keywords: Disease Outbreak News; ProMED-mail; World Health Organization; early detection; emerging infectious diseases; global health; health security; international health regulations; outbreaks; public health emergencies of international concern; surveillance; undiagnosed diseases.