Multiple introductions of highly pathogenic avian influenza H5N1 clade 2.3.4.4b into South America

Since 2020, multiple outbreaks of the clade 2.3.4.4b of the highly pathogenic avian influenza (HPAI) viruses of the H5N1 subtype have been reported in many countries in Europe, Asia, Africa, and North America [1]. This specific clade has led to great concern due to its rapid intercontinental distribution, transmission efficacy in new species of birds and the frequent infection of different wild terrestrial and marine mammals with atypical neurotropism and the concerning sporadic human cases [2]. The clade 2.3.4.4b arrived to the Americas in late 2021, causing high mortalities in domestic and wild birds since then [3]. According to the CDC, in April 26, 2023, more than 6715 cases has been reported in Wild birds; 58,789,351 poultry affected and 1 human case in the US and the numbers continues growing (https://www.cdc.gov/flu/avianflu/avian-flu-summary.htm). In October 2022, HPAI reached South America and was officially reported for the first time in Colombia and later in Peru, Ecuador, Venezuela, Chile, Argentina, Bolivia, and Uruguay.