Global Respiratory Virus Activity Weekly Update N° 488 Summarizing data through Week 31, ending 04 August 2024 Summary Influenza In the Northern hemisphere, activity in temperate countries remained at interepidemic levels. Activity was elevated in a few countries in Central America and the Caribbean, Middle Africa, Western Africa, Southern Asia and South East Asia. Influenza A(H3N2) viruses predominated except in Western Asia, South East Asia and Southern Asia where A(HIN1)pdm09 viruses predominated. Activi ...

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].