Nucleic acid detection, such as for HtrA (a 47-kDa periplasmic serine protease), the 56-kDa type-specific antigen rrs (16S rRNA), and groEL (the heat shock protein Hsp60), is accurate in the early phase of infection (until 10 days after the onset of fever), after which serology becomes superior for the diagnosis of scrub typhus [18]. Here, HTRA1 is linked to scrub typhus.