Answer:
There were several endeavors in the 20th century that led to drastic reductions in the mortality from infectious disease in the United States. Here are three examples:
Improved public health infrastructure: The establishment of public health agencies and the implementation of effective disease prevention and control measures, such as vaccination programs and clean water initiatives, played a major role in reducing the mortality from infectious disease in the United States.
Antibiotic development: The discovery and development of antibiotics in the mid-20th century revolutionized the treatment of bacterial infections and significantly reduced mortality from infectious disease.
Improved sanitation and hygiene: Improved sanitation and hygiene practices, such as the widespread use of hand washing and the implementation of effective sewage treatment systems, also contributed to the reduction of mortality from infectious disease in the United States.