Interpretation is complicated for flavivirus infections because a positive Zika‐IgM test can result from cross‐reactivity of serum containing antibodies against dengue virus.21 Because chikungunya is an alphavirus, there is no serological cross‐reactivity with the flaviviruses, making diagnosis more straightforward (in areas where other alphaviruses are not circulating). Here, CD40LG is linked to Flavivirus Infections.