Complex sentence: An outbreak started in Brazil in 2015, and rapidly spread to the Americas, Pacific, Asia and Africa, leading the World Health Organization declared it a Public Health Emergency of International Concern in February 2016.
Split into simpler sentences: An outbreak started in Brazil in 2015, and spread to the Americas, Pacific, Asia, and Africa. This lead to the World Health Organization declared it a Public Health Emergency of International Concern in February 2016.