Prevalence of the H5N8 influenza virus in birds: Systematic review with meta-analysis

Introduction: Avian influenza viruses are members of the Orthomyxoviridae family, considered highly pathogenic (HPAI). They result from genetic variations from their low virulence predecessors. HPAI is a global problem. Large outbreaks of HAPI have significant health and economic impacts. Objective: The objective of this study was to assess the prevalence of the H5N8 Influenza virus in birds, as well as to assess its variability according to the countries and years. Methods: A systematic review of the literature was carried out in six databases (Web of Sciences, Scopus, PubMed, SciELO, Lilacs and Google Scholar) to evaluate the proportion of birds infected with the H5N8 Influenza virus, by molecular and immunological techniques. A meta-analysis was performed using a random-effects model to calculate the pooled prevalence, 95% confidence intervals (95%CI). A 2-tailed 5% alpha level was used for hypothesis testing. Measures of heterogeneity were estimated and reported, including the Cochrane Q statistic, the I² index, and the tau-squared test. In addition, bird species performed subgroup analyzes. Results: 152 data groups were analyzed, a combined prevalence of 1.6% (95% CI 1.3–1.9%) was found for molecular studies, and the ELISA study yielded a seroprevalence of 66.7%; those results of molecular detection varied by year, from 0.2% in 2014 to 52.6% in 2020 and 96.9% in 2015. Conclusion: The combined prevalence was substantial because large outbreaks have caused severe economic repercussions. In addition, it is considered a serious concern for public health due to its possible zoonotic activity.