Germ theory, long before it led to medical treatments, drove down mortality rates by revolutionizing sanitation and hygiene

Draining the swamp. Jason Crawford. The Roots of Progress, Jan 28. https://rootsofprogress.org/draining-the-swamp

Excerpts (the original link has references & lots of charts... interesting throughout):

And the surprising thing I found is that infectious disease mortality rates have been declining steadily since long before vaccines or antibiotics.

I was surprised to learn that sanitation efforts began as early as the 1700s—and that these efforts were based on data collection and analysis, long before a full scientific theory of infection had been worked out. James Riley, in “Insects and the European Mortality Decline”, writes:3

In the later decades of the seventeenth and early decades of the eighteenth century, a number of internationally renowned physicians … formulated specific measures of intervention. Relying on Hippocratic tradition, specifically, on its suggestion that endemic and epidemic diseases are caused by forces in the environment, and influenced by Renaissance efforts at urban sanitation, these physicians proposed to discover the meteorological and topographical forces that might be blamed for the onset of epidemics. Toward this end, they and their followers embarked on a vast campaign to assemble qualitative and quantitative data about epidemics, climate and weather, geographical and topographical signs, and other features of the habitat. Their aim was to find conjunctures or correlations in the data, occasions when epidemics occurred after the same complex of environmental forces. Early signs of such a complex would offer warnings and allow the adoption of measures of prevention and avoidance. This body of medical theory failed to produce a coherent list of correlations, but it did provide a specific body of measures of avoidance and prevention.

In particular, they proposed (each bullet quoted from the article):

. to drain swamps, bogs, moats, and other sites of standing water
. to introduce hydraulic devices that would circulate water in canals and cisterns
. to flush refuse from areas of human habitation
. to ventilate living quarters and meeting places and to burn sulfur sticks or apply other insecticidal measures in houses, hospitals, prisons, meeting halls, and ships
. to inter corpses outside the city
. and by other measures, including refuse burial, to detach humankind from organic waste

These reforms were implemented starting in the 1740s, some by local and central governments, others by “humanitarians acting on private initiative”.

What broad changes were actually implemented, and is it plausible that they had a significant impact?

To have had a significant effect on insect numbers, the measures proposed by the environmentalists [the physicians advocating environmental cleanup] would have had to have been broadly applied across western Europe. Two measures, lavation and drainage, are particularly important in insect control, and we can focus on examples of their application. Lavation combines programs taking three forms: flushing filth from urban sites, collecting and disposing of refuse, and introducing devices to agitate or circulate standing water. By these means, which would cleanse streets, industrial sites, and buildings, and transform standing water in canals and cisterns into moving water, the environmentalists argued, the city might be made as healthy as the countryside. One model for these proposals was the naturally washed site of the town of Chester, England, where rain periodically flushed refuse into a subterranean drainage network cleansed by tidal action. The objective of the environmentalists was to introduce the same action by hydraulic engineering. Another model was the program followed in Hamburg to collect and dispose of refuse outside the city each day. A third was the improvement of streets by paving and widening, and of urban drainage networks by constructing or expanding sewage systems. Measures of one or another variety were adopted in many British cities and towns in the Improvement Acts of the 1760s and thereafter, and observers, such as William White in York, attributed declines in mortality specifically to them. In Paris, the drainage system was improved in 1740, and later in the century, other measures, including the emptying of cesspits and the installation of sewers, followed. In the Austrian Empire, Johann Peter Frank directed a broad campaign of medical policing, which included projects for refuse collection and disposal.

These efforts affected not only diseases such as malaria, where insects are the primary vector of infection, but also others such as dysentery in which insects (especially flies and cockroaches) can distribute the disease throughout the environment, e.g., from waste to food. Pest control thus provides the best explanation I’ve found for reductions in the mortality rate from the mid-1700s to early 1800s.

Cutler & Miller estimate10 that

the introduction of water filtration and chlorination systems led to major reductions in mortality, explaining nearly half of the overall reduction in mortality between 1900 and 1936. Our results also suggest that clean water was responsible for three-quarters of the decline in infant mortality and nearly two-thirds of the decline in child mortality. The magnitude of these effects is striking. Clean water also appears to have led to the near eradication of typhoid fever, a waterborne scourge of the 19th and early 20th Centuries.

Finally, the germ theory led to public health efforts to educate the populace on good general hygiene. A policy brief by Samuel Preston says:9

Enlightened public health officials were quick to recognize how the germ theory should guide their practice. Furthermore, by the time of the first White House Conference on Infant Mortality, held in 1909, they realized that rapid advances in longevity required that public officials go beyond their normal domain of public works and attempt to change the personal health practices of individuals. The germ theory provided a number of powerful weapons for doing so. These included boiling bottles and milk, washing hands, protecting food from flies, isolating sick children, and ventilating rooms. Public health officials launched massive campaigns to encourage these practices. In New York City, milk depots were established with the ostensible purpose of distributing milk to indigent mothers but with the real purpose, according to the director, of instructing mothers in hygienic practices. The New York City Department of Health produced one of the nation’s first motion pictures, entitled The Fly Pest. At the national level, the new Children’s Bureau adopted a primary focus on child health. Its pamphlet called Infant Care became the largest selling volume in the history of the Government Printing Office, with some 12 million copies sold by 1940. By the 1920s, the bureau was receiving and answering over 100,000 letters a year from parents seeking child care advice.

Thus the germ theory, long before it led to medical treatments, drove down mortality rates by revolutionizing sanitation and hygiene.