Clinical and socio-demographic data were collected using structured questionnaires after obtaining written informed consent from study participants. Venous blood (5 ml) was collected aseptically by disinfection with 70% alcohol and 2% tincture of iodine, transferred into sterile 45 ml tryptose soy broth (Oxoid, UK) with 0.6% yeast extract (TSBYE) [26] and transported within 1h to the SNNP Regional Public Health Laboratory.