Pandemics, Epidemics, Endemics, The Fundamentals
Epidemiology, Infectious Disease Spread and Dissemination Principles
Apr 26, 2009
Epidemiology is a word of Greek origins. It means epi- (among), demos- (population, people), -ology (from logos, study of), therefore, the study of the spread of disease among the people. There are all kinds of epidemics, including famines or food epidemics, overeating epidemics, drug epidemics and, most importantly, infectious disease epidemics.
Endemic, Epidemic and Pandemic
Imagine a person, living and surviving, isolated and alone, camped out in a tent in a large forest with no one around for hundreds of miles. Imagine another person, scurrying to and fro in a city of 10-20 million. This person eats, talks, socializes, transports publicly on a train and bus, and lives a full life of constant, high-intensity human to human contact, directly and indirectly, every day for a year. Oh, by the way, imagine each of these two persons has active, untreated tuberculosis, wherein a single bacterium is capable of initiating TB in a susceptible human. Indeed, one does not have to imagine a nightmare worse than this to see the devastation of epidemic. In the first case, it matters little, no one else is around. In the second case, it matters much, multitudes are involved.
Epidemiologists are those professionals who find, track and attempt to curtail or thwart disease among populations or people. Epidemiologists ask such questions as:
- What is going on here?
- What is causing this?
- Who has this and how many have this?
- Where is it, where has it been, and where is it going?
- Can it be curtailed, stopped or treated?
- What preventive measures can be taken, must be taken?
This is all about What?, Who?, When?, and Where?. These are simple questions seeking answers. Ultimately, it is all about stopping the infectious disease in the case of influenza, tuberculosis, AIDS, chickenpox or whatever. It is aimed at preventing illness (morbidity) and death (mortality).
The following definitions are relevant:
- Endemic, the normal disease situation in a defined location or place. This means the normal incidence of infectious diseases such as hepatitis, or influenza, or salmonellosis, etc..
- Epidemic, an outbreak, an increase above normal epidemic levels. Epidemic might be a few cases, if there are none normally, or currently. It might be a dozen, a hundred, or several thousand.
- Pandemic, disease spreading, or threatening to spread, throughout the globe, covering the entire planet. The epidemic flu of 1918–1919 was a true pandemic. AIDS is a pandemic.
Understanding New and Old Epidemics
Remember these basic ideas and any epidemic becomes more understandable:
- Epidemics have a beginning. See Figure photos below for influenza and a mold epidemic.
- Epidemics may begin and end quickly. Food poisoning due to infected potato salad at a picnic would be such a case.
- Epidemics and pandemics may extend for weeks, months, years or decades. Influenza epidemics are months to a year and there are usually periods where there is local epidemic, but no pandemic. Then, a new epidemic may spread world-wide. Swine flu, avian flu, or a new human flu may suddenly emerge. AIDS is a clear example of ongoing, expanding and uncontrolled pandemic now approaching 30 years since it was first recognized. Tuberculosis is an ongoing, chronic pandemic.
- Knowledge of the disease and agent of the infectious disease is important as Robert Koch was able to prove with his Postulates. These two ideas enable all to learn how to prevent infection and disease, what are the treatments, and what precautions need to be taken. Treatment might include anti-viral agents, antibiotics, preventative vaccines, or other medical interventions.
Role of CDC, WHO, National CDC and the Media in Epidemiology
Being uniformed about disease is not an option in the modern world. Viruses and bacteria can travel at the speed of an international flight, a trade wind or the jet stream today. Thousands to millions of people can become quickly exposed to infectious entities and soon a whirlwind of epidemic is sewn. The role of state, federal, national and world organizations is more important than ever. Heeding advice as it is forthcoming can save a life. Radio, television, the Internet, phones are all valuable in this close-knit world.
Stay tuned, remember in life, and epidemiology, it is important to be alert, informed, concerned, active, and resourceful – human lives depend on these attitudes now, and in the future.
Sources:
CDC (US). 2009. Human Swine Influenza Investigation.
Greenberg, R.S. et al. 2001. Medical Epidemiology. Third Ed., Lange Medical Books/McGraw-Hill, New York. 215 pp.
 |
 |
 |
 |
 |
