IT was during a beach clean last week that we noticed them – first a dead guillemot, washed up on the sand, then another dead bird, further down a beach, and yet another, so decayed it was hard for us to tell what it was. I wondered then if this was avian flu, if the disease that had already had a catastrophic impact on Shetland’s seabird population. Now, here, killing the birdlife in the Firth of Forth?

But we didn’t report them to DEFRA’s hotline, as I now realise we should have done. Rather we just stared at the bodies in sadness. Then the news emerged that the outbreak epicentre had moved south and it seemed clear that those birds must have succumbed to the disease experts are calling highly pathogenic avian influenza.

This current epidemic is predominantly caused by a new, particularly deadly and pathogenic variant of the avian flu virus H5N1 – and widely understood to have originated in intensive farming in East Asia before being passed on to wild birds. The result is, as Dr Peter Walton, Head of Species and Habitats for RSPB Scotland, has put it, a “new and unprecedented” impact on bird populations.

More than 383,000 bird deaths from the virus have been counted by the World Organisation for Animal Health (WOAH) since October last year. This might seem relatively small, given that we are now used to talking about global deaths of over 6 million humans through Covid, but it is devastating.

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Huge numbers of barnacle geese were killed by the virus in the Solway, with an estimated loss of around a third of the Svalbard population. Some experts believe that 10 percent of UK gannets may have been lost to the disease. When a disease has that kind of impact, it can be hard for the population to recover, particularly when gannets live for 17 years and only lays one egg per year.

These seabirds, of course, are not only threatened by avian flu – but also by climate change, and the shift of their food source, fishing and other human disturbances.

Those wet carcasses washed up on our beaches, aren’t just sad – they speak of a world we have cultivated. Avian flu may not itself be human-made, but, as a UN Food and Agriculture Organisation report recently described, such highly pathogenic avian influenza outbreaks are typically associated with “domestic poultry production”. When the viruses spill back over into wild bird populations – as they have done numerous times since the 2000s – the disease can be carried trans-continentally by bird migrations.

Attempts, of course, have been made to try to stop the spread of the disease in and through poultry farming in the UK. It was only in May that, after five months of mandatory indoor housing of poultry, farms were allowed to rear them outdoor again. The UK has recorded 121 cases of bird flu on farms since October, ten of which were in Scotland. The poultry sector is naturally concerned that restrictions will be imposed again

So far, this avian flu virus has remained entirely based within bird populations and the risk to humans is considered very low – but not zero. With so much virus circulating in birds across the globe, there is good reason for concern that, through mutations and genetic exchanges, this virus may at some point gain the ability to jump to humans and then transmit between humans.

China, for instance, has reported 20 human cases of H5N6 bird flu this year (almost all of which had exposure to live poultry) though no confirmed cases of human-to-human transmission.

The coronavirus pandemic has raised awareness of how interactions between humans, wild animals and intensive agriculture may all be part of the story of how disease mutates, spills over and spreads. Covid alerted us to how much infectious disease is rooted in ecological change and food production. Studies have found that zoonosis emergence is often “linked to agricultural intensification and environmental change”.

One of the questions we must ask ourselves is whether it is how, globally, we farm poultry that is part of the problem. Another is whether climate change is part of this story. Many experts say it is. Climate and environmental change creates movement and migration – generating situations where species make new contacts and pathogens jump more easily to new susceptible hosts.

Increasingly, the UN and WHO are talking of a “one health” strategy – in which the health of humans, of our agricultural animals, and of wildlife and wider planet are considered one and connected. Such a joined-up approach is vital. We are all connected, and avian flu is just another reminder of how we create the conditions of disease, not just for animals, but for ourselves.