The early 1900s represented a public health environment vastly different from today, characterized by a persistent struggle against immediate biological threats. Life expectancy for a newborn in the United States around 1900 hovered at only 47.3 years of age. This low average was largely a consequence of extremely high mortality among infants and young children; nearly 40% of all deaths occurred in children under the age of five. The leading causes of death were fundamentally different from the chronic conditions that dominate modern mortality statistics.
Infectious Diseases as the Primary Mortality Threats
Acute infectious diseases were the single greatest threat to life in the early 20th century, collectively accounting for approximately one-third of all deaths. The three most common causes of death were Pneumonia and Influenza, Tuberculosis, and Diarrhea and Enteritis. These transmissible diseases spread rapidly through communities, often striking down individuals within days or weeks.
Pneumonia and influenza were the top killers, especially during seasonal outbreaks, demonstrated by the 1918 influenza pandemic. Tuberculosis, often called “consumption,” was a lingering bacterial infection that primarily affected the lungs. At the turn of the century, this single disease was responsible for 194 deaths per 100,000 residents. Diarrhea and enteritis were severe gastrointestinal infections, frequently transmitted through contaminated food and water, and were particularly lethal to infants. Even heart disease was often linked to infectious agents, as conditions like rheumatic fever frequently led to long-term cardiac damage.
Societal Conditions Fueling High Death Rates
The widespread prevalence of these infectious diseases was supported by the societal and environmental conditions of the era. Rapid urbanization resulted in severely overcrowded living arrangements, which facilitated the easy transmission of airborne diseases like tuberculosis. Poor housing conditions allowed germs to spread efficiently between individuals living in close proximity.
Sanitation infrastructure lagged behind the pace of population growth in cities, creating environments where waterborne diseases flourished. Many communities lacked centralized sewer systems and filtration for public drinking water supplies. This failure meant that diseases like typhoid and gastrointestinal infections were a constant hazard. Furthermore, there were virtually no effective medical treatments to stop these infections once they took hold, as the development of antibiotics was still decades away.
The Epidemiological Transition
A historic shift began to occur in the subsequent decades, fundamentally altering the pattern of mortality in the United States—a process known as the Epidemiological Transition. The leading causes of death transitioned from acute, communicable infections to chronic, degenerative diseases. This change was driven primarily by major public health reforms.
Widespread implementation of water chlorination and the construction of effective sewer systems drastically reduced waterborne diseases. Improved food handling, better nutrition, and personal hygiene contributed to lowering infection rates. The later introduction of mass vaccination programs and the development of antibiotics provided the medical breakthroughs necessary to conquer remaining infectious threats. As infectious disease deaths plummeted, the average lifespan increased dramatically, rising from 47.3 years to over 78 years. This extended lifespan meant people lived long enough to succumb to conditions associated with aging, leading to heart disease, cancer, and stroke becoming the primary mortality concerns.