About Public Health
What is public health?
Public health is the science of protecting and improving the health of a population, as well as the communities where they live, work, learn, and play.
It is achieved through promoting healthy lifestyles, conducting research on disease and injury prevention, and detecting and responding to infectious diseases. Public health connects us all.
Why is public health important?
Public health is responsible for monitoring and identifying repeating trends in a community that have or could have negative impacts on the people who live, work, play, and learn there. Public health also works to reduce health disparities in populations where one group is disproportionately affected by negative outcomes compared with another. Our goal is to prevent people from needing medical care through educational programs, policy changes, research, and the administration of preventive services such as immunizations.
As an example:
City A has a population of 50 people; 25, or 50%, died from cancer in the last 5 years. City B, which also has a population of 50 people, has 5 people, or 10%, who have died from cancer in the last 5 years. Essentially, the difference between these two populations reflects a health disparity based on where they live, work, learn, and play. Accordingly, we would attempt to identify what distinguishes the two populations.
For instance, do those in city A work in a high-risk environment, such as working with asbestos? Or do those in city B have higher access to clinical care that diagnoses and treats cancer earlier than those in city A? Evaluating these factors is essential to improving the health of the population in city A. If they lack clinical care, adding a doctor could have a profound impact on reducing the mortality rate.
Public health is also crucial for responding to threats such as natural disasters, disease outbreaks, epidemics, and pandemics.
History of public health in application
One of the most famous examples of public health in action is the lesson of Dr. John Snow and the Broad Street Pump.
John Snow was an obstetrician providing care for the residents of London, England, in the mid-1800s. He made a startling observation that changed the way we view disease and prevention. Around 1831, the first case of cholera was documented in England. Over the next 20+ years, tens of thousands of people in England died from cholera. Dr. Snow observed many cases and a significant outbreak in Soho in 1854. He postulated that the source of the outbreak was the drinking water used by the people.
In the 1800s, waste and untreated raw sewage were collected into cesspools and/or dumped in the River Thames. Dr. Snow believed that these actions had the potential to contaminate the drinking, cooking, and bathing water collected in the area wells. Additionally, water companies often bottled water from the Thames and delivered it to pubs, breweries, and other businesses where it was distributed to the populations living, working, playing, and learning there.
Testing his theory
With the Soho outbreak, he set out to prove his theory. He began his investigation by gathering information from hospitals and public records to determine the origin of the outbreak. The investigation included a geographic grid to map deaths from the outbreak and assess access to the Broad Street pump. Dr. Snow found that within 250 yards of the spot where Cambridge Street joins Broad Street were upwards of 500 fatal attacks of cholera in 10 days, the location of the Broad Street Pump. Dr. Snow also investigated people who did not have cholera to determine if they used the pump and to rule out other potential sources.
In September 1854, Dr. Snow presented his research to town officials and convinced them to take the handle off the pump, making it impossible to draw water. Although reluctant to believe him, the officials complied as a trial, and the outbreak of cholera almost immediately trickled to a stop. Learn more about Dr. Snow and the Broad Street Pump.
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- Page reviewed/updated: March 23, 2026
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Kentucky Department for Public Health