The World Health Organization has updated a list of diseases that pose a public health risk because of their epidemic potential. Using a published prioritization methodology, the list was first reviewed in January 2017, WHO said. The second annual review occurred on February 6-7. Experts consider that given their potential to cause a public health emergency and the absence of efficacious drugs and/or vaccines, there is an urgent need for accelerated research and development for Crimean-Congo hemorrhagic fever (CCHF), Ebola virus disease and Marburg virus disease, Lassa fever, Middle East respiratory syndrome coronavirus (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS), Nipah and henipaviral diseases, Rift Valley fever (RVF), Zika and Disease X. “Disease X represents the knowledge that a serious international epidemic could be caused by a pathogen currently unknown to cause human disease,” the organization said.