The scrub typhus 'exposed' cohort (STE) will consist of children and adults recruited from two villages in an area where scrub typhus is reported as a common disease. This cohort has a high risk of previous contact with scrub typhus, and it is unknown if they had an asymptomatic or sub-clinical infection in the past, but we expect the presence of some form of immune memory regarding cellular and/or humoral immunity in a large proportion of these subjects.