Public Health Emergency of International Concern second PHEIC was issued in May 2014 with the resurgence of polio after its near-eradication, deemed "an extraordinary event." On Friday, August 8, 2014, the World Health Organization declared its third Public Health Emergency of International Concern in response to the outbreak of Ebola in Western Africa. On Monday, February 1, 2016, the World Health Organization declared its fourth PHEIC in response to clusters of microcephaly and Guillain–Barré syndrome in the Americas, which at the time were suspected to be associated with the ongoing outbreak of Zika virus. Later research and evidence bore out these concerns; in April, the WHO
World Health Organization letters related thereto, and taking into account the respective co-ordinating responsibilities of both organizations, it is recognized by the World Health Organization that the International Atomic Energy Agency has the primary responsibility for encouraging, assisting and co- ordinating research and development and practical application of atomic energy for peaceful uses throughout the world without prejudice to the right of the World Health Organization to concern itself with promoting, developing, assisting and co-ordinating international health work, including research, in all its aspects.” Clearly suggesting that the WHO is free to do as it sees fit on nuclear, radiation and other matters