CD40LG and infection: In contrast, IgM positivity was significantly higher in primary infections for DENV (73% vs. 39%, p < 0.001), JEV (56% vs. 30%, p = 0.003), TBEV (17% vs. 5%, p = 0.036), and WNV (25% vs. 3%, p < 0.001), suggesting probable recent infections (Table 1).