Seasonal Respiratory Infection and Exacerbation of Chronic Cardiopulmonary Disease (A Narrative Review)

Relevance: Respiratory viral infection peaks seasonally and is linked to exacerbation of chronic cardiopulmonary disease, but whether this link is uniform across conditions, and whether circadian- and vitamin D-related immunity contributes independently, remains unclear. Goals and Objectives: To synthesize evidence on the seasonal association between respiratory infection and exacerbation of chronic obstructive pulmonary disease (COPD), asthma, congestive heart failure (CHF), and idiopathic pulmonary fibrosis (IPF), and to evaluate circadian/vitamin D immune variation as a candidate mechanism. Materials and Methods: A narrative synthesis of PubMed and Scite literature (2021-2026, one earlier source retained) used Boolean searches for seasonality, respiratory infection, and exacerbation; seventeen sources were retained. Results: Respiratory infection showed a consistent winter peak coinciding with COPD, asthma, and CHF exacerbation. This association was disease-specific: COPD/asthma seasonality weakened sharply during pandemic-era infection suppression and rebounded, while IPF exacerbations retained winter seasonality independent of infection. A UK Biobank cohort (n=329,261) showed confounder-independent seasonal immune variation, supporting a complementary circadian pathway; vitamin D's protective role was inconsistent. Conclusions: The infection-exacerbation link is disease-specific: strongest for COPD/asthma, less definitive for CHF, insufficient for IPF. Circadian/vitamin D immune variation remains a plausible, unproven complementary factor, supporting existing seasonal prevention over new protocols.

Keywords: seasonality, respiratory infection, COPD exacerbation, idiopathic pulmonary fibrosis, circadian immunity, vitamin D.