Transcriptomic Responses for the Identification of Pathogens

FEBRILE ADULTS- INCLUSION CRITERIA * Age greater than or equal to 15 years and less than or equal to 65 years * Participant is willing and they and/or an appropriate guardian/relative/representative is able to give informed consent for participation in the study and a follow-up (telephone) discussion at 14 days * And either: 1. Febrile illness without localising features (see 'exclusion criteria' and 'screening' sections) where fever is defined as: * documented tympanic/rectal temperature of ≥ 38°C or an axillary/oral temperature of ≥ 37.8°C, or a reported fever within the last 24 hours and * Reported duration of fever 3-14 days or 2. Recently confirmed blood culture indicating enteric fever (confirmed within the previous 5 days) * They may have had recent exposure to antimicrobials. FEBRILE ADULTS- EXCLUSION CRITERIA * The participant may not enter the study if ANY of the following apply: * Unable to provide informed consent and no next of kin is willing and able to provide informed consent. * For patients with febrile illness (included in (1) above): Any history or clinical suspicion of: * Rheumatological or connective tissue disorder (e.g. Rheumatoid arthritis) * Autoimmune condition (e.g. Autoimmune Hepatitis) * Malignancy * Active treatment with immunomodulating medications, or for tuberculosis (pulmonary or extrapulmonary) or any other chronic infection. * Pregnancy (breast feeding mothers will NOT be excluded) * No hospitalisation for more than 48 hours in the last 4 weeks * Vaccination within 4 weeks prior to current admission * Localising signs or symptoms of infection sufficient to diagnose the likely cause of acute febrile illness and thus prevent it from being 'undifferentiated.' CONTROLS- INCLUSION CRITERIA * Participant is willing and they are (and in 15-18 year olds, a guardian is) able to give informed consent for participation in the study * Age greater than or equal to 15 years and less than or equal to 65 years * They live outside of the normal/local catchment area for each hospital site * Afebrile (as defined by no reported fever and temperature ≤ 38°C or an axillary/oral temperature of ≤ 37.8°C). CONTROLS- EXCLUSION CRITERIA * The participant may not enter the study if ANY of the following apply: * Unable to provide informed consent and no next of kin (or parent/guardian in the case of a minor) is willing and able to provide informed consent. * Current treatment for or prior history, or clinical suspicion of: * Rheumatological or connective tissue disorder * Autoimmune condition * Malignancy * Active treatment for tuberculosis (pulmonary or extrapulmonary) or clinical suspicion of active tuberculosis. Previous completed treatment is not a reason for exclusion. * Active treatment with immunomodulating medications or any other chronic infection. * Pregnant (breast feeding mothers will NOT be excluded) * Hospitalisation within 4 weeks of recruitment * Vaccination within 4 weeks prior to recruitment * Antimicrobial use within 4 weeks of recruitment * Participant reports feeling more unwell than usual on the day of enrolment. EXPLORATORY AIMS- PAEDIATRIC CRITERIA; INCLUSION CRITERIA * Age greater than or equal to 2 years and less than 15 years * As above for adult participants. EXPLORATORY AIMS- PAEDIATRIC CRITERIA; EXCLUSION CRITERIA * Parent/guardian is unwilling, and/or patient aged 8 to 14 years is unwilling to assent to provide informed consent. * As above for adult participants.