CD40LG and scrub typhus: However, an IFA-based nationwide study among healthy people in Bhutan found a considerably higher seroprevalence rate of 22.6% (IgG titer ≥1:256 or IgM titer ≥1:1024) [20], which probably reflects a higher incidence of scrub typhus in Bhutan (62 cases per 100,000 in 2015) [21] than in South Korea (18.5 cases per 100,000 in 2015) [9].