How pathogens made the modern world

When it finally reached Ireland, it caused potato crop failures that killed around one million people between 1845 and 1852, mostly because of epidemics of typhus (caused by Rickettsia prowazekii bacteria) and a bacterial infection known as relapsing fever. [...]even if a decrease in population did occur on that scale - and there is plenty of circumstantial evidence that economic and other activities were not that severely affected - correlation is not causation. The reduction in tuberculosis infections in the United Kingdom might be partly thanks to improved public-health regulations, but probably mainly because of the increased availability of affordable protein-rich food: by 1910, there were 25,000 fish and chip shops in the country.