Respiratory Syncytial Virus and Other Respiratory Viruses in Hospitalized Infants During the 2023-2024 Winter Season in Mexico.

Respiratory syncytial virus (RSV) is the leading cause of lower respiratory tract infections in young children. During the COVID-19 pandemic, a significant change in the epidemiology of RSV and other viruses occurred worldwide, leading to a reduction in the circulation of these infectious agents. After the pandemic, the resurgence of seasonal respiratory viruses occurred, but some features of these infections contrast to those registered prior to the pandemic. In the present work, we studied 390 children <5 years old admitted to the hospital to determine the contribution of RSV, SARS-CoV-2, human metapneumovirus (hMPV), and influenza viruses to acute respiratory infections during the 2023-2024 winter season in Mexico. RSV was the most frequently detected virus (n = 160, 41%), followed by SARS-CoV-2 (n = 69, 17.7%), hMPV (n = 68, 17.4%), and influenza A or B (n = 40, 10.26%). Fourteen patients required admission to the intensive care unit, including six (42.8%) with RSV infection. Four children died (1%). At least one of the four viruses was detected in all deceased patients: SARS-CoV-2 in one; SARS-CoV-2 and hMPV in two; and RSV, influenza A, and SARS-CoV-2 in one. The high impact of RSV and other respiratory viruses indicates the need to implement specific preventive programs to reduce the morbidity and mortality associated with them.