“The avian influenza virus continues to spread in the European Unionand elsewhere, causing high mortality among wild birds, spillovers (species jumps, ed.) between wild and domestic mammals and outbreaks on farms”. This was highlighted by the European Food Safety Authority EFSA, in a note in which he takes stock of what emerges from a scientific report, signed together with the European Center for Disease Prevention and Control (ECDC), in which the risk factors for a potential influenza pandemic and related mitigation measures.
How transmission occurs
What are the drivers that could drive viral evolution? Experts have identified “some species of farmed fur animals (e.g. mink or foxes), which are highly susceptible to influenza viruses as possible spreading factors,” the note highlights. “Although mammal-to-mammal transmission has not yet been confirmed, wild mammals could act as 'bridge' hosts between wild birds, domestic animals and humans. Even companion animals, such as cats, that live in home and have access to the outside, in open air environments they can be a potential transmission vehicle”, warn the EU authorities.
Farming in areas rich in waterfowl, with outdoor production and/or poor biosecurity “may facilitate the introduction of the virus onto farms and its further spread”, continues EFSA. “Extreme weather events and climate change play an additional role in the evolution of the situation because they can affect the ecology and demography of wild birds and thus influence how the disease develops over time, the experts found.”
Outbreaks on farms
This is therefore the current situation illustrated by the two EU bodies. A picture that sees “avian influenza viruses remaining prevalent among wild bird populations in the EU and the European Economic Area”. An element to which is added the observation of “transmission phenomena between species of birds and mammals, in particular on fur farms, where outbreaks have been reported. Although transmission from infected birds to humans is rare – we read in an extract from the report which also takes stock of mitigation measures and the importance of a 'One Health' strategy – cases of exposure have occurred since 2020 to these viruses without any symptomatic infections having been reported in the EU/EEA”.
However, the authors warn, “these viruses continue to evolve globally and, with the migration of wild birds, new strains carrying potential mutations may be selected for adaptation to mammals. If avian influenza A/H5N1 viruses If they acquired the ability to spread efficiently between humans, large-scale transmission could occur due to the lack of immune defense against H5 viruses in humans. The emergence of avian influenza viruses capable of infecting mammals , including humans, can be facilitated by various factors.”
Measures to mitigate the spread of avian flu
One Health measures to mitigate the risk of these viruses adapting to mammals and humans “focus on limiting exposure and preventing spread,” it says. Key options are “strengthening surveillance, targeting humans and animals, ensuring access to rapid diagnosis, promoting collaboration between the animal and human sectors and implementing preventive measures such as vaccination”. “Effective communication” should then be promoted, as well as the “strengthening of veterinary infrastructures, the application of biosecurity measures on farms and the reduction of contact between wildlife and domestic animals. For effective risk reduction, an 'careful planning of poultry and fur farming activities, especially in areas with a high density of waterfowl.'
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