Industrial chicken farming is accelerating the spread of the world’s most common bacterial cause of diarrhoea, scientists have found. The study found a dramatic increase in the exchange of campylobacter strains between wild birds and chickens as farming has intensified, creating ideal conditions for the bacteria to mix, spread and acquire new traits. The latest work suggests that the evolution of the infection is being fuelled by the unprecedented scale of chicken production. Since the 1960s, global chicken numbers have increased seven-fold to approximately 27 billion birds, accounting for about 70% of all bird biomass on earth. The industrialisation of chicken farming has led to affordable animal protein at scale, but also presents new health risks.