This natural history study sought to estimate the proportion of subjects who had confirmed Zika, Chikungunya, or Dengue virus (including co-infections) from subjects who presented fever and/or rash in southeastern Mexico. The study also compared the clinical signs, symptoms, and laboratory abnormalities associated with acute Zika, Chikungunya, and Dengue infection. The Zik01 study started on June 2016 and was completed on January 2019 with an enrollment of 600 participants.