Title : Severe influenza and other related respiratory infection cases during Omicron era in Japan
Abstract:
Introduction: We had severe respiratory infection cases after COVID-19 pandemic in Japan. At first, three cases of severe influenza that required ventilator management in the 2024-2025 season, which was a major influenza season in Japan, are presented.
Case series:
Case 1: A 54-year-old man with obesity developed lobar pneumonia as a result of severe community-acquired pneumonia (CAP) secondary to methicillin-susceptible Staphylococcus aureus, as confirmed on sputum culture. The nasal swab was positive for influenza A antigen. Intravenous peramivir and piperacillin/tazobactam were administered for 2 days followed by lascufloxacin and linezolid for 2 weeks. Veno-venous extracorporeal membrane oxygenation (ECMO) was also performed after intubated ventilator management.
Case 2: A 63-year-old man with multiple myeloma and chronic kidney disease developed severe pneumonia as a result of CAP. Although influenza A antigen was detected, no bacteria were isolated from blood cultures or respiratory specimens. He showed severe hypoxia and massive ground-glass opacities in both lung fields, but he recovered after administration of peramivir and levofloxacin with prednisolone for 2 days and 2 weeks, respectively, with non-invasive positive pressure support.
Case 3: A 43-year-old man without any related medical history developed severe heart failure with mild bronchopneumonia and was admitted to our hospital; influenza A antigen was detected from the nasal swab. Acute heart failure caused by myocarditis and CAP were suspected and were effectively treated with peramivir and percutaneous ventricular assist device (IMPELLA), which involved an auxiliary circulating pump with veno-arterial ECMO for 1 day and 2 weeks, respectively, with intubated ventilator management.
Conclusions: In three middle-aged patients, influenza virus may have accelerated the secondary bacterial pneumonia, pure viral pneumonia, and myocarditis. All three patients had not received influenza vaccines and were not elderly. Although most of all vaccines have been made light after the COVID-19 pandemic appears to have subsided, we should reinform the importance of influenza vaccines and improvement of critical care protocols, including other respiratory infections, such as COVID-19, RS virus infection, and pneumococcal pneumonia cases.
