Influenza virus infection contributing to the majority of viral pneumonia, acute cardiovascular and renal co-morbidities even death, is a worldwide public health concern caused by seasonal and pandemic influenza viruses. Unlike seasonal influenza, which occurred annually, the emerging of pandemic influenza every two to three decades for the distinctly reassorted influenza virus strains contributed to the broadly rapid spread and increased morbidity and mortality. While the majority of the influenza-infected population manifest no or only moderate influenza like illnesses symptoms, partial would progress to severe influenza illness and even die for the influenza-triggered complications. In this view, we collect and recapitulate various biomarkers that have been identified and may be employed in the clinical practices involved detection, treatment, and protection of individuals with a high risk of progression to severe influenza illnesses, as well as accurate track monitoring of influenza illnesses prognosis and applicability of therapeutic strategies. While numerous influenza-related deaths occurred in the aging and frail population, the biomarkers associated with increased susceptibility to severe influenza illnesses among the aging and frail patients were retrieved and outlined. Aging intertwined with frailty, they have similar physiological function decline processes resulting in dysfunction of host defense mechanisms and increased infection-related co-morbidities. Overall, these potential biomarkers associated with aging, frailty conditions, and impaired immune defense mechanisms are determinant factors of influenza illness severity through combining the baseline background and tipping points, as well as socioeconomic status disparity and psychosocial vulnerability being the shifting the trajectory and outcomes of influenza illnesses, particularly among the elder individuals.
© 2025. The Author(s).