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During the COVID-19 pandemic, nonpharmaceutical interventions (NPIs) were implemented in order to control the transmission of SARS-CoV-2, potentially affecting the prevalence of respiratory syncytial virus (RSV). This review evaluated the impact of NPIs on RSV-related hospitalizations in children during the lockdown (2020-2021) compared to the pre-pandemic (2015-2020) and post-lockdown (2021-2022) periods. In this systematic review and meta-analysis, we searched through PubMed, Scopus, and Web of Science for studies published in English between 1 January 2015 and 31 December 2022. Additionally, we conducted hand searches of other records published between 1 January 2023 and 22 January 2024. Our target population was hospitalized children aged 0-18 years with RSV-related lower respiratory tract infections confirmed through immunofluorescence, antigen testing, or molecular assays. We focused on peer-reviewed observational studies, analyzing the primary outcome of pooled RSV prevalence. A generalized linear mixed model with a random-effects model was utilized to pool each RSV prevalence. Heterogeneity was assessed using Cochran's Q and I 2 statistics, while publication bias was evaluated through funnel plots and Egger's tests. We identified and analyzed 5815 publications and included 112 studies with 308,985 participants. Notably, RSV prevalence was significantly lower during the lockdown period (5.03% [95% CI: 2.67; 9.28]) than during the pre-pandemic period (25.60% [95% CI: 22.57; 28.88], p < 0.0001). However, RSV prevalence increased notably in the post-lockdown period after the relaxation of COVID-19 prevention measures (42.02% [95% CI: 31.49; 53.33] vs. 5.03% [95% CI: 2.67; 9.28], p < 0.0001). Most pooled effect estimates exhibited significant heterogeneity ( I 2 : 91.2% to 99.3%). Our findings emphasize the effectiveness of NPIs in reducing RSV transmission. NPIs should be considered significant public health measures to address RSV outbreaks.

Respiratory syncytial virus (RSV) is the main cause of severe respiratory infections in young children. The need for global epidemiologic data regarding RSV has been increasingly recognized. RSV A infections are reported more frequently than RSV B. Nonetheless, the temporal distribution of infections caused by both RSV groups has not been investigated globally. A systematic review was carried out regarding published studies on RSV A and B epidemiology, as well as RSV G gene ectodomain sequence data available at GenBank. A total of 76,668 [45,990 (60%) RSV A and 30,678 (40%) RSV B] positive samples from 83 countries were identified and included in the analysis. Genotype assignment was obtained in 5,340 RSV A and 2,518 RSV B sequences. Two patterns of RSV circulation were observed: continuous seasons with RSV A predominance and alternate predominance of RSV A and B. These patterns were observed in all regions, but the predominant RSV group seldom coincided in all continents during a given year or season. The most frequently identified RSV A genotype was NA1 (including ON1 viruses) (76.30%), and the most frequently identified RSV B genotype was BA (70.65%). Multiple genotypes circulated simultaneously throughout the evolutionary history of RSV, but genotype diversity decreased after the year 2000. The classification of RSV group and genotype is important for the development of vaccines, as well as to understand viral dynamics. This study displays the global and continental RSV circulation patterns from the first report of human RSV infection until the end of 2020.

Human metapneumovirus (HMPV) is an important respiratory pathogen and is divided in two main groups (A and B). HMPV strains with partial duplications (111-nt and 180-nt duplication) of the G gene have been reported in recent years. Since the initial reports, viruses with these characteristics have been reported in several countries. We analyzed all complete HMPV G gene ectodomain sequences available at GenBank to determine if viruses with 111-nt or 180-nt duplication have become the leading HMPV strains worldwide, and to describe their temporal and geographic distribution. We identified 1462 sequences that fulfilled study criteria (764 HMPV A and 698 HMPV B) reported from 37 countries. The most frequent HMPV A genotype was A2b2 ( n = 366), and the most frequent B genotype was B2 ( n = 374). A total of 84 sequences contained the 111-nt duplication, and 90 sequences contained the 180-nt duplication. Since 2016, viruses with a partial duplication comprise the most frequent HMPV A sequences globally and have displaced other HMPV A viruses in Asia, Europe, and South America; no sequences of viruses with partial duplication have been reported in North America or Africa so far. Continued surveillance of HMPV is required to identify the emergence and spread of epidemiologically relevant variants.

Influenza is a leading cause of respiratory tract infections worldwide and there is limited information on the impact of the influenza A(H1N1)pdm virus on mortality after the 2009 pandemic. Using national mortality register data through 1998-2015 in Mexico, influenza-associated mortality was estimated for respiratory, cardiovascular, and all-cause events. The proportion of influenza-associated respiratory and cardiovascular deaths among different age groups were compared. There were 8,853,986 death registries included for the 1998-2015 winter seasons, average influenza-associated respiratory, cardiovascular, and all-cause mortality rates were 5.2, 6.3, and 19.6 deaths/100,000 population, respectively. The largest number of respiratory influenza-associated deaths occurred in adults 60 years of age and older, followed by children <5 years of age; during the 2009 pandemic, 2011-2012, and 2013-2014 winter seasons there was a larger number of deaths in the 20-59 years old group. Influenza-associated mortality rates showed a continuous reduction in children <5 years of age. After the 2009 pandemic, influenza A(H1N1)pdm09 virus-associated mortality in Mexico showed a persistent change in the demographic pattern of the most severely affected population, particularly during the 2013-2014 season. Influenza associated-mortality has decreased in children <5 years of age and continue to be elevated in adults >60 years of age.