# Expanding Horizons: Host Range Evolution and Treatment Strategies for Highly Pathogenic Avian Influenza H5N1 and H7N9

## TL;DR

This paper discusses the evolving host range of H5N1 and H7N9 avian influenza viruses and their implications for public health and treatment strategies.

## Contribution

The paper highlights recent mammalian adaptations and transmission patterns of H5N1, emphasizing the need for surveillance to prevent pandemics.

## Key findings

- H5N1 has infected U.S. dairy cattle and caused 71 human infections, with cow-to-cow transmission observed.
- Mammal-to-mammal transmission has been documented in foxes and marine mammals.
- Standard pasteurization effectively inactivates the virus in milk.

## Abstract

Avian influenza viruses (AIVs), including H5N1 and H7N9, from the Orthomyxoviridae family present substantial public health concerns. The predominant circulating clade 2.3.4.4b has demonstrated enhanced capacity for mammalian adaptation, raising concerns about potential reassortment with human seasonal influenza viruses. Unlike H7N9’s limited host range, H5N1 infects birds, various mammals, and humans. Recent concerns include widespread H5N1 infection of U.S. dairy cattle across 18 states, affecting over 1000 herds with 71 human infections (70 H5N1 and 1 H5N5). Key observations include cow-to-cow transmission, viral presence in milk, and transmission to humans, mainly through occupational exposure. Evidence of mammal-to-mammal transmission has been documented in European and Canadian foxes and South American marine mammals. Standard pasteurization effectively inactivates the virus in milk. The continuing mammalian adaptations, particularly mutations like PB2-E627K, PB2-D701N, and PB2-M535I, suggest potential for further evolution in new hosts, emphasizing the need for enhanced surveillance to mitigate pandemic risks.