ADE during a secondary heterologous Dengue virus infection has been documented in vitro, in mice, in non-human primates, and in humans playing a key role in the worsening of the clinical presentations. In contrast, ADE of Zika virus by pre-existing immunity to Dengue virus can be induced in vitro, and in immunodeficient mice. However, there is no evidence to support ADE occurring in non-human primates or in humans.