Data Sheet 1_From molecular evolution to the school health room: the role of community-based public health nurses (helsesykepleiere) in one health communication on cross-species influenza transmission in Norway.docx

<p>Highly pathogenic avian influenza (HPAI) A(H5N1) clade 2.3.4.4b viruses have undergone an unprecedented expansion of host range since 2021, moving from wild birds and poultry into dairy cattle, domestic cats, and other mammals, with sporadic human infections in Europe and North America (Food and Agriculture Organization et al., 2025a; Rolfes et al., 2025). This expansion is underpinned by well-characterised molecular mechanisms of influenza A virus evolution — antigenic drift, gene segment reassortment, and receptor-binding adaptation — that shape the frequency and direction of cross-species spillover (McDonald et al., 2016; Steel and Lowen, 2017; Man et al., 2026).

Norwegian wild-bird and mammalian surveillance data document recurrent incursions of clade 2.3.4.4b viruses, and international risk assessments continue to describe low, but non-zero, human risk concentrated among individuals with close animal contact (World Health Organization, 2025–2026; Ytrehus et al; European Food Safety Authority et al., 2025a). Translating this fast-moving virological and epidemiological evidence into everyday protective behavior for children, adolescents, and families remains an underdeveloped link in pandemic preparedness, compounded by documented gaps in adolescent One Health literacy (Zucca et al., 2021).