Subjects living in the scrub typhus endemic region of Ubon Ratchathani, Northeast Thailand (n = 105), had a mean IFN-γ ELISpot response of 189 SFC / 106 PBMC (95% CI 88–290), compared to 40 SFC / 106 PBMC (95% CI 9–71) in subjects living in a non scrub typhus endemic area (Bangkok, Thailand, n = 14) some of whom may have grown up in or travelled to an endemic part of Thailand, and 3 SFC / 106 PBMC (95% CI 0–7) for subjects in Oxford, UK (n = 12) who had never encountered scrub typhus. The gene discussed is IFNG; the disease is scrub typhus.