Introduction: Novel influenza viruses (NIV) are a specific type of influenza A virus that differs from the seasonal flu viruses currently circulating among humans. These viruses often originate in animals, such as birds or pigs, and can infect humans. Public health officials are particularly concerned about novel viruses. The goal of this study is to determine whether individuals infected with NIV have a higher risk of hospitalization and mortality. Methods: We used deidentified and publicly available data for a population-based cohort study of adults admitted to intensive care units of acute care hospitals in Texas from Q1 2016 through Q2 2024 with a principal diagnosis of influenza. Hospitalizations transferred to or from another hospital, nonemergency admissions, and hospitalizations discharged against medical advice were excluded. The target population was identified using International Classification of Diseases. Tenth Revisions, Clinical Modification (ICD-10-CM) codes selected from Clinical Classification Software Refined Category10 RSP003: Influenza. The primary outcome was short-term mortality. Overlap propensity score weighting was applied with results expressed as adjusted risk ratio and 95% confidence interval (aRR 95% CI). Results: Of the 15,301 hospitalizations included in the study, 790 (5%) had novel influenza A virus, 1,983 (13%) had unidentified influenza A virus, and 12,258 (82%) had identified influenza A virus. The distributions of age and sex were not statistically different between the groups with most other covariates showing either insignificant or only small differences between the groups. Short-term mortality was similar between the groups 3.8% for both novel and unidentified influenza A virus vs 4.4% for identified influenza A virus. On adjusted analyses, virus classification was not associated with either in hospital or short-term mortality; aRR 1.0 95% CI 0.7 to 1.5 for novel vs identified and aRR 1.2 95% CI 0.7 to 2.0 for novel vs unidentified. Conclusions: Although a presumption could be that there is no developed immunity to NIV, over the last 9 years, it has had no impact on either the frequency of hospitalization or short-term mortality. It is possible that traditional flu vaccination can reduce the risk of hospitalization and death from either of the flu viruses.
Brown et al. (Sun,) studied this question.