Respiratory tract infections place a burden on vulnerable nursing home (NH) populations. We aimed to develop a sentinel network to monitor influenza-like illness (ILI), including COVID-19, among Belgian NH residents.
Following a two-year pilot study, an observational sentinel surveillance was initiated in October 2022. A geographically representative sample was established for Belgium using the number of NH beds as a proxy for NH residents. Throughout the year, weekly epidemiological/clinical data is collected on the number of ILI cases, ILI-related hospital admissions and deaths at NH level using an online questionnaire. During the flu season (as determined by the WHO: week 40-20), two nasopharyngeal samples are collected weekly per NH for viral typing with RT-qPCR.
During season 2022-23 (October 2022 to September 2023), 34 NH representing 2,943 residents (2.1% of all Belgian NH residents) participated a complete season. We observed two peaks of new ILI cases of 20 per 1,000 residents: one in mid-December 2022, and one in February 2023. The first peak coincided with the ILI increase observed in the network of general practitioners (GP) and the latter could be attributed to one outbreak (1). Since April 17, 2023 (week 16), the incidence remained below the low threshold (7 per 1,000 residents per week). From August 28, 2023 (week 35) onwards, ILI incidence increased again with the approaching start of the flu season (Figure 1). During season 2022-23, 37 ILI related deaths were reported. Out of 56 nasopharyngeal samples retrieved, 24 were negative and the majority were either positive for SARS-CoV-2 (10) or for seasonal corona (8). One co-infection was reported.
Comparing the results with these of the ILI sentinel network of GP we can conclude that our findings seem to follow the ILI situation among the general Belgian population. A sentinel network is a feasible way to monitor ILI in NH setting. As of season 2023-24, the network is being expanded to generate more robust findings and to enable regional reporting.