Differences in characteristics of adult patients hospitalized with influenza-like illness during the 2018/2019 flu season

Abstract

Introduction, objectives: A significant burden of morbidity and mortality is caused by seasonal outbreaks of respiratory viruses. Our aim was to identify clinical and microbiological differences among adult patients hospitalized with acute respiratory infection (ARI) or influenza-like illness (ILI). Methods: A single-center observational cohort study was conducted at South Pest Central Hospital, National Institute of Hematology and Infectious Diseases during the 2018/2019 influenza season. Patients were identified using the hospital database, and included in the study if respiratory PCR sampling was done during hospital stay. Subgroups were created according to the identified etiology: clinical ILI/ARI (no PCR positivity), PCR positive ILI/ARI with influenza, PCR positive ILI/ARI with other virus(es). Primary outcome was the occurrence of any complication, secondary outcomes were in-hospital all-cause mortality, intensive care unit (ICU) admission, length of stay (LOS) and ICU LOS. For statistical analysis, Mann–Whitney and Fisher’s tests were used. Results: From 112 identified cases, 42.8% were caused by influenza A or B, 7.1% by other viruses, notably RSV. PCR positivity frequently associated with prior hospitalization (23.2% vs. 42.8%; p = 0.04), and shorter time from symptom onset to diagnosis (3.0 ± 4.0 vs. 4.0 ±5.0 days, p = 0.02). Complication rates were similar among subgroups (46.4% vs. 51.8%; p = 0.72), with pneumonia as a leading complication (45.5%). ICU admission was necessary in 5.4%, in-hospital all-cause mortality was 3.6%. Median LOS and ICU LOS were 8.5 ± 8.0 and 20.5 ± 30.5 days, respectively. Conclusion: During the 2018/2019 season, most ILI/ARI cases were caused by influenza, but other respiratory viruses could also be detected in lower rates. Pneumonia was the most common complication. Respiratory PCR sampling might provide a feasible way of etiology identification.