and a case report of a fetus with brain anomalies and decreasing head size from whose brain live Zika virus was isolated.16 On the basis of our update of their analysis, which incorporates newly available evidence nearly all the relevant criteria have been met, with the exception of the presence of experimental evidence. However, Hill emphasizes that meeting all nine criteria is not necessary40; instead, the criteria should serve as a framework to assess when the most likely interpretation of a relationship is causation.