C

Reasoning: An endemic level is the constant or usual frequency of a disease in a population. Since 48 cases fall within the facility’s normal weekly range of 40–50 cases, the situation reflects the expected background occurrence, i.e., endemicity, rather than an excess (epidemic/outbreak) or irregular single cases (sporadic) [Ashraf 2020 PMID 32040709; Yeoh 2019 PMID 31205246].