CD40LG and Flavivirus Infections: In areas where PRNTs are not performed, positive dengue and negative Zika virus IgM antibody tests should be interpreted as a “presumptive recent dengue virus infection,” positive Zika and negative dengue virus IgM antibody tests should be interpreted as a “presumptive recent Zika virus infection,” and positive dengue and Zika virus IgM antibody tests should be interpreted as a “presumptive recent flavivirus infection.” If only one IgM antibody test was performed and was positive and PRNT was not performed, the second IgM test should be performed.