TF and infection: 2. To assess the immune response to natural TF, PF, and iNTS infections over a 1-year follow-up period a. Assessment of the magnitude and duration of the immune response to TF, PF, and iNTS after natural infection b. Identification and validation of immunological markers associated with the development of Salmonella Typhi, Salmonella Paratyphi, and iNTS carriage