Updated joint FAO/WHO/WOAH assessment of recent influenza A（H5N1） virus events in animals and people

Investment Rating - The global public health risk of influenza A(H5N1) viruses is assessed as low, with a low to moderate risk of infection for occupationally exposed individuals depending on risk mitigation measures in place [2][31][30]. Core Insights - The A(H5N1) virus has been detected in various animal species, including dairy cattle, leading to significant ecological consequences and health risks in both wildlife and livestock [3][12][14]. - Human infections with A(H5N1) viruses have been limited, with 35 cases reported since 2021, primarily associated with exposure to infected animals or contaminated environments [20][29]. - The ongoing spread of A(H5N1) in dairy cattle in the USA has raised concerns about potential zoonotic transmission, necessitating a One Health approach to effectively manage avian influenza [4][30]. Summary by Sections Infections in Animals - A(H5N1) viruses, particularly clade 2.3.4.4b, continue to diversify and spread, causing mass die-offs in wild birds and infections in various mammal species [11][12]. - As of July 2024, 162 dairy cattle herds in 13 states in the USA tested positive for A(H5N1), with clinical signs observed in 10 to 15% of affected cows [14][31]. Detections in Humans - Since 2021, 35 human cases of A(H5N1) have been reported, with most cases linked to direct exposure to infected animals [20][29]. - The majority of human cases have been asymptomatic or mild, with no evidence of sustained human-to-human transmission [22][25]. Virus Characteristics - Virus sequences from human cases have not shown markers for reduced susceptibility to antiviral treatments, indicating limited adaptation to mammalian hosts [26][30]. - Genetic markers associated with mammalian adaptation have been identified in some cases, warranting ongoing monitoring [17][26]. Recommended Actions - Increased surveillance for A(H5) influenza viruses in domestic and wild birds is recommended, along with prompt reporting of HPAI events [34][35]. - Countries are advised to implement biosecurity measures in livestock holdings and ensure proper hygiene practices when handling animal products [35][37].