Children aged 0.3 months to 14 years who presented with AES were tested for scrub typhus using serum IgM Enzyme-Linked Immunosorbent Assay (ELISA) and polymerase chain reaction (PCR) of cerebrospinal fluid (CSF) and peripheral blood mononuclear cells (PBMC). The gene discussed is CD40LG; the disease is scrub typhus.