c. 460 BCE Hippocratic medicine links health and environment Texts associated with the Hippocratic tradition relate health to water, air, and place, anticipating later public-health thinking. 1377 Ragusa adopts quarantine measures The Adriatic port of Ragusa institutes isolation measures for arrivals from plague-affected areas, a milestone in quarantine history. 1662 John Graunt analyzes Bills of Mortality Graunt's statistical study of London mortality records helps found demography and epidemiology. 1796 Jenner performs the first successful vaccination Edward Jenner's cowpox experiment leads to the development of vaccination against smallpox. 1842 Chadwick publishes report on sanitary conditions Edwin Chadwick's report links disease to poverty and unsanitary urban living conditions and drives sanitation reform. 1848 Britain enacts the Public Health Act The Public Health Act creates a national framework for sanitary reform in Britain. 1854 John Snow investigates the Broad Street outbreak Snow's cholera investigation in Soho becomes a foundational case in modern epidemiology. 1867 Major London sewer works are completed The completion of Joseph Bazalgette's main sewer system becomes a landmark in urban sanitation. 1876 Koch identifies the anthrax bacillus Robert Koch's work strengthens germ theory and transforms disease control and public-health science. 1902 Pan American Sanitary Bureau is founded The bureau, later the Pan American Health Organization, is established for international disease coordination in the Americas. 1906 Pure Food and Drug Act becomes law The United States adopts federal regulation of food and drug safety after years of reform campaigning. 1918 Influenza pandemic spreads worldwide The 1918 influenza pandemic demonstrates the global scale of modern public-health emergencies. 1946 Centers for Disease Control is founded The Communicable Disease Center is established in the United States and later becomes the CDC. April 7, 1948 World Health Organization is established The WHO comes into force as the principal international body for public health. 1955 Salk polio vaccine rollout begins Mass vaccination campaigns using the Salk vaccine become a major public-health achievement. 1978 Alma-Ata Declaration emphasizes primary health care A WHO and UNICEF conference in Alma-Ata declares primary health care central to public health strategy. 1981 First official reports of AIDS appear The early recognition of AIDS marks the start of a major global public-health crisis. 1988 Global Polio Eradication Initiative launches International agencies begin a coordinated campaign to eradicate polio worldwide. 2005 Revised International Health Regulations are adopted WHO member states adopt revised International Health Regulations to strengthen global outbreak reporting and response. March 11, 2020 WHO declares COVID-19 a pandemic The World Health Organization characterizes COVID-19 as a pandemic, marking a defining moment in twenty-first-century p…