Causative agents

• Hunter Gatherers - ten thousand years ago humans were hunter- gatherers. They had a short span, but not because of epidemics, their primary problem was just finding enough food to eat. They lived and travelled in small groups and hunted and foraged for food. Their mixed diet was probably fairly balanced and nutritionally complete. Since they lived in small groups and moved frequently, they had few problems with accumulating waste or contaminated water or food.
• Mythology, Superstition and Religion - early explanations of occurrence of disease focused on superstition, myths and religion. Primitive people believed in natural spirits that were sometimes mischievous or vengeful. The Greeks believed that the god Jupiter was angry about man accepting the gift of fire. The story is long and complicated, but Zeus crammed all the diseases, sorrows, vices and crimes that afflict humanity into a box and gave it Epimetheus, the husband of Pandora. Pandora wanted desperately to know what was in the box, she waited until Epimetheus was gone. She opened the box, and all of the ills of the world flew out and spread throughout the human world.
• The Agricultural Revolution - the shift from the hunter-gather mode of living to an agricultural mode provided a more secure supply of food and enabled expansion of the population. However, domesticated animals provided not only food and labor; they also carried diseases that could be transmitted to humans. People also began to rely heavily on one or two crops, so their diets were often lacking in protein, minerals and vitamins. People began living in larger groups and staying in the same place, so there was more opportunity for transmission of diseases. Garbage and waste accumulated, and rodents and insect vectors were attracted to human settlements, providing sources of disease.
• The Hippocratic Corpus - for many centuries explanations for disease were based not on science, but on religion, superstition, and myth. The Hippocratic Corpus was an early attempt to think about diseases, not as punishment form the gods, but as an imbalance of man with the environment. Although it was unsophisticated by today's standards, it was an important step forward. By considering the possibility that diseases were associated with environmental factors or imbalances in diet or personal behaviors, the Corpus also opened up the possibility of intervening to prevent disease or treat it.
• Bubonic Plague


  An acute infectious disease caused by the bacterium Yersinia pestis. The bacteria live in the intestines of fleas and are transmitted to rats by flea bites. The rats therefore, serve as a natural reservoir for the disease, and fleas are the vectors. Occasionally, an infected flea would jump to a human and introduce the bacteria when the blood meal was taken. The bacteria would then spread to the regional lymph nodes and multiply, causing dark, tender, swollen nodules (buboes). As the infection spread, the victim would experience headache, high fever, delirium, and finally death in about 60% of cases.
• Cause of the Plague and Strategies for Prevention - the cause of plague was not known, but there were many theories. The most popular explanation was that it was caused by "miasmas", invisible vapors that emanated from the swamps or cesspools and floated around in the air, where they could be inhaled. Others thought it was spread by person to person contact, or perhaps by too much sun exposure, or by intentional poisoning. The miasma theory was the most popular, however.
• While most believed that plague was caused by miasmas, the primary mode of transmission was actually via flea bites, and, in sense, the real causes were increased population density and failure to dispose of garbage. Accumulations, of garbage attracted rats and enabled the rat population to explode. Rats had harbored fleas and Yersinia pestis for many years without major difficulty, and plague epidemics in humans didn't occur until human behaviors created environments that brought people into proximity with rats, fleas and Yersinia pestis. These were the real causes of plague epidemics.
• Causative agent, Vector, Species, Reservoir

  • Yersinia pestis
  • Rats and Rodents
  • Bacteria
  • Garbage
• Systematic thinking about how to establish the determinants of health and disease was not suddenly invented by a single individual. It evolved over centuries. One can see sparks of insights intermittently over time. In the 1700s and 1800s one can see attempts to examine the causes of disease and the effectiveness of prevention and treatment in a systematic way.
• John Graunt - The Bills of Mortality (1662)


  Graunt made a number of observations regarding common causes of death, higher death rates in men, seasonal variation in death rates, and the fact that some diseases had relatively constant death rates, while others varied considerably. Graunt also estimated population size and rates of population growth, and he was the first to construct "life table" in order to address the issue of survival from the time of birth.
• Anton van Leeuwenhouk (1670s)


  Van Leeuwenhouk's accomplishments were preceded by those of Robert Hooke, who had published "Micrographia" in 1665. Hooke devised a compound microscope and used it to examine and describe the structure of nature on a microscopic level, including insects, feathers and plants. In fact, it was Hooke who discovered plant cells and coined the term "cells". Anton van Leeuwenhouk of Holland was the "father of microscopy". He used these to create the first useful microscopes. Using his inventions, he was the first to see bacteria (1674), yeast, protozoa, sperm cells, and red blood cells.
• John Pringle and "Jail Fever" (1740s)


  John Pringle was a Scot who served as physician general to British forces during the Was of the Austrian Succession (1740-48). He proposed a number of measures aimed at improving the health of soldiers including improvements in hospital ventilation and camp sanitation, proper drainage, adequate latrines, and the avoidance of marshes. He wrote expensively on the importance of hygiene to prevent "typhus" or "jail fever", which was a common malady among soldiers and prisoners in jails. Pringle also coined the term "ïnfluenza".
• James Lind and Scurvy (1754)


  Scurvy is due to deficiency in vitamin C that results in weak connective tissue and abnormally fragile capillaries that rupture easily, causing bleeding, anemia, edema, jaundice, heart failure and death. Scurvy was a huge problem in sailors several centuries ago, because of the chronic lack of fresh fruit and vegetables during a long sea voyages. James Lind, a Scottish naval surgeon, suspected that citrus fruits could prevent it base on some anecdotal observations.
• Francois Broussais & Pierre Louis (1832)

  Francois Broussais used blood letting to treat many diseases, including cholera. It is believed that his vigorous use of blood letting to treat victims of a cholera epidemic in Paris substantially contributed to the mortality rate. Pierre Louis was a contemporary of Broussais's who believed in using numerical methods to evaluate treatment. Louis studied bloodletting and found it ineffective, by many dismissed his conclusions.
• Ignaz Semmelweis and Oliver Wendell Holmes (1840s)


  Ignaz Semmelweis was a Hungarian physician wo practiced in the maternity department of Vienna General Hospital in the 1840s. postpartum sepsis (puerperal fever) was a common occurrence and was almost invariably fatal. He required attendants to wash hands with chlorinated water to control spread of infection.

  Oliver Wendell Holmes, Sr. was an American physician, professor, lecturer and literary author. He advocated for medical reforms and was a strong proponent of the idea that doctors and nurses could carry puerperal fever from patient to patient. In 1843, he presented a paper entitled "The Contagiousness of Puerperal Fever" at the Boston Society for Medical Improvement.
• John Snow - The Father of Epidemiology


  John Snow was a physician in London who spent several decades studying cholera in a systematic way. He is most often credited with solving and outbreak of cholera that occurred in London in 1854.
• Edwin Chadwick and the Sanitary Idea

  in 1842, Sir Edwin Chadwick, a social reformer, published a report entitled the "Report into the Sanitary Conditions of the Labouring Population of Great Britain" proving that life expectancy was much lower in towns than in the countryside.

  Chadwick was instrumental in creating a central public health administration that paved the way for drainage, sewers, garbage disposal, regulation of housing, and regulations regarding nuisances and offensive trades. This "sanitary idea" resulted in remarkable improvements in health and well-being.
• Louis Pasteur (late 1800)

  Louis Pasteur was a French biologist and chemist who made enormous contributions to germ theory, to prevention of food spoilage, and to the control of disease. In 1853 Pasteur began studying fermentation in wine and beer and rapidly concluded that microorganisms were responsible. He also discovered that microbes in milk could be killed by heating to about 130 degrees Fahrenheit, a process which is now known as 'pasteurization'. He discovered that some microorganisms require oxygen (aerobic organisms), while others reproduce in the absence of oxygen (aerobic).

  Pasteur pioneered the idea of artificially generating weakened microorganisms as vaccines. Edward Jenner's work had demonstrated the principle with the naturally occurring cowpox, which could be used to vaccine against smallpox. Pasteur was able to artificially weaken strains of anthrax and cholera in order to generate vaccines.
• What is Public Health?

  Public health is the "science and art of preventing disease, prolonging life and promoting human health through organized efforts and informed choices of society, organizations, public and private, communities and individuals."

  In 1920 Charles Edward A. Winslow defined public health as "the science and art of preventing disease, prolonging life, and promoting physical health and efficiency through organized community efforts, control of community infections, the education of the individual in principles of personal hygiene, the organization of medical and nursing service for the early diagnosis and preventive treatment of disease, and the development of the social machinery which will ensure to every individual in the community a standard of living adequate for the maintenance of health." While most would include mental health as an important aspect of public health today, Winslow's definition is still relevant today.
• Health is dependent on a complex interplay among an array of genetic, environmental, and lifestyle factors. As a result, public health is built on expertise and skills from many areas, including biology, environmental and earth science, sociology, psychology, government, medicine, statistics, communication and many others. This complexity makes it difficult for the general public to understand exactly what is public health and what it does.
• The strategy employed by public health

  1. Identify and define health problems

  2. Identify the determinants, i.e. the factors associated wit the problem (risk factors)

  3. Develop and test interventions to control or prevent the problem

  4. Assess the effectiveness of interventions
• Achievements of public health

  • Decline in death from cardiovascular disease
  • Improvements of maternal and child health
  • Family planning
  • Fluoridation of drinking water
  • Reduction in the prevalence of tobacco use
• Community


  A group of people who share a common place, experience or interest. We often use this term for people who live in the same area: the same neighborhood, the same city or town, and even the same state or country.
• Community health


  A major field of study within the medical and clinical sciences which focuses on the maintenance, protection and improvement of the health status of population groups and communities as opposed to the health of individual patients. It is a distinct field of study that may be taught with a separate school of public health or environmental health.
• Public health includes community health. It is concerned with threats to health based on population health analysis. Public health incorporates the interdisciplinary approaches of epidemiology, biostatistics and health services, environmental health.
• Examples of communities people may see themselves as part of

  • Racial or ethnic community (e.g. Filipino community, Chinese community)
  • Religious community (e.g. Muslim community, Christian Community, Hindu Community)
  • Community of people with disabilities (e.g. those with visual impairments, developmental disabilities, or mental illness)
• Community health


  A major field of study within the medical and clinical sciences which focuses on the maintenance, protection and improvement of the health status of population groups and communities as opposed to the health of individual patients
• Public health


  Includes community health, concerned with threats to health based on population health analysis, incorporates interdisciplinary approaches like epidemiology, biostatistics, health services, environmental health, community health, behavioral health, health economics, public policy, insurance medicine and occupational health
• Community health


  A discipline concerned with the study and improvement of the health characteristics of different communities, tends to focus on geographical areas
• The world today faces threats like HIV/AIDS, diabetes, waterborne diseases, zoonotic diseases, and antibiotic resistance leading to the re-emergence of infectious diseases such as tuberculosis
• Primary healthcare


  Health interventions that aim to reduce risk factors and increase health promotion and prevention
• Secondary healthcare


  Acute care administered in hospital department settings
• Tertiary healthcare


  Highly specialized care usually involving disease or disability management
• Referral process


  Begins at home where patient experiences illness, patient seeks care from health professional, performs self-care/self-medication or seeks alternative treatment, if necessary patient is brought to health station/unit, if critically ill patient is transported to referral facility, if higher level of care is required patient is brought to hospital
• First delay


  Delay in patient deciding to seek care from health professional
• Second delay


  Delay in transporting patient from health unit/clinic to referral facility
• Third delay


  Delay in provision of healthcare to patient at hospital
• Quarantine is the separation of an individual who has possibly been exposed to disease, while isolation is the separation of an individual who has the disease
• Quarantine dates back to the 14th century during the Black Death pandemic, when lepers were isolated from healthy individuals
• Public health


  The science and art of preventing disease, prolonging life, and promoting physical health and efficiency through organized community efforts