The Etiology of Acute Febrile Illness Requiring Hospitalization

Inclusion Criteria: * Age ≥1 year * Acute febrile illness requiring hospitalization (fever defined as temperature recorded ≥38.0°C during the first 24 hour period of hospitalization). * Hospitalized within the past 24 hours. * Willing to allow storage of blood and other specimens for use in future studies of infectious diseases. Exclusion Criteria: * Hospitalized within the past 3 months, not including current hospitalization for acute febrile illness. * Inpatient transfer from another hospital. * A known medical disorder or other circumstance, which in the opinion of the PI might make the participation of the individual unsafe or difficult. Examples include, but not limited to: mental illness which could affect compliance with protocol, an anemic patient preventing blood draw.