In Kisantu Health Zone, approximate population 200,000, fever surveillance will be implemented in 8 health centers and 1 tertiary hospital. Individuals presenting to one of these study facilities with acute fever or history of fever or individuals presenting with suspicion of intestinal perforation irrespective of fever status, will be considered for enrollment. Following consent, blood samples (between 2.5 ml for children and 22 ml for adults) will be collected from eligible subjects and demographic and clinical information will be recorded in study forms at the time of enrollment at study health centers and hospitals. Peritoneal fluid and ileal tissue samples will be collected from surgical patients where possible. Biological specimens will be used for various testing, including microbiological culture of blood, tissue and peritoneal fluid for confirmation of bacterial growth, malaria diagnostics (microscopy and rapid testing), and storage of tissue samples for pathological investigation, and biobanking. Hospitalized patients will be followed-up to track clinical outcomes for the duration of hospitalization.

Inclusion Criteria:

At health center:

1. Patients of all ages currently living in the catchment area of the health center presenting to healthcare facility with objective fever of at least 38.0°C tympanic or 37.5 °C axillary OR
2. Patients of all ages currently living in the catchment area of the health center presenting to healthcare facility with reported fever ≥3 consecutive days within 7 days of presentation

At Hospital:

1. Suspicion of intestinal perforation/peritonitis due to typhoid fever requiring surgery for patients living in and outside the catchment area (even in the absence of laboratory confirmation) OR
2. Patients living in the catchment area of the hospital with invasive salmonellosis confirmed through blood-culture surveillance embedded in routine patient cares

Exclusion Criteria:

• Individuals who do not provide informed consent

The health care structure in the Democratic Republic of Congo is divided into Health Zones, each subdivided into Health Areas. Each Health Area contains first-line Health Posts and second-line Health Centers, which refer patients requiring advanced care to the Health Zone referral hospital. The study population includes both urban and rural areas and includes approximately 200,000 residents. The greatest distance from remote areas to the tertiary hospital is 80km.