In the coming weeks, bacon sandwich eaters in Newcastle and dairy farmers in California may find their pockets hit by developments thousands of miles away. The culprit is an outbreak of African swine fever which is sweeping through Asia, leading to the culling of millions of pigs in China and Vietnam, in what one expert calls the world’s biggest animal disease outbreak to date. The US and the UK are watching keenly. Denmark has built a 43-mile border fence to keep out wild boar. The devastating impact in Asia and the consequences already being felt further afield shed light on the globalisation of modern food production.

The highly infectious disease is harmless to humans but fatal to pigs; there is, as yet, no vaccine. It was first detected outside Africa in 1957, in Portugal. It re-emerged in Europe more recently. But never before has it spread so rapidly and damagingly. In China, which until this outbreak reared around half the world’s pigs, every province has been affected. The disease has already shown up in Mongolia, Cambodia and North Korea. The UN Food And Agriculture Organization says it believes the cases reported by governments are underestimates. Many farmers may quietly sell infected meat rather than relying on promises of compensation and enmeshing themselves in disease-control obligations. Officials may also be reluctant to own up to problems.

The knock-on effects are already apparent. As China looks for alternative pork sources, prices for EU-reared pork are said to be rising. In the US, dairy farmers whose whey feeds Chinese pigs fear demand is dropping. Smallholders feeding pigs swill have been implicated in this outbreak, while globalised food chains have helped spread it far and wide. Some see the solution to such problems in large-scale, industrialised production in units with thousands of pigs, in place of the family farms that have dominated production in China. The country has already been following the lead of the US and then Europe in supersizing its livestock farms, with the aim of stabilising food prices and improving biosecurity and food safety standards. For all the bucolic associations of the word “farming”, increasingly, around the world, animals are reared not on green fields but in giant sheds.

But to regard such methods as a panacea is wildly naive and potentially dangerous. Experts have long acknowledged the specific health risks posed by intensive units, including the opportunities they provide for pathogens to mutate. In 2015, agricultural officials following the bird flu outbreak in America’s midwest noted that backyard flocks seemed mostly unscathed while intensive farms had been badly hit. When a disease does hit a megafarm, it is likely to spread faster through densely concentrated herds and the scale of the units means that many more animals are affected. Campaigners say that animals are also more susceptible to falling sick due to stress from their cramped, grim and inhumane surroundings, and the fact that they are bred for fast growth rates and large litter sizes, with scant regard for their health. Industrial farming tends to rely on just a few breeds, with further potential to reduce resistance. And its heavy reliance on antibiotics, with the routine dosing of large herds, has been linked to the rise in antibiotic resistance.

Larger companies are easier to inspect and hold accountable, and more likely to be able to afford disease control measures. But they too have profits to protect, and more political clout. This is why campaigners fear that Brexit could lead to lowered standards, closer to those of the US than the EU, in terms of animal welfare, food safety (chlorine-washed chicken), environmental and other concerns – whether through a trade deal with the US, shaped by its megaproducers, or a race to the bottom to produce cheap food.

This time, the impact has been on the welfare of pigs and the finances of humans. We may not be so lucky with another disease. What happens in Guangxi or Iowa now has implications for the rest of us, not only in the price we pay for our food, but also for our health and wellbeing. Our modern system of food production comes at a cost, and not only to the animals that are its raw materials.