The word epidemic is derived from Greek word ‘epi’ meaning upon or above and ‘demos’ meaning people. The term is used to describe a situation where a disease spreads rapidly to a large number of people in a given population over a short time period. When the term epidemic is used in connection with infectious disease, it is due to the sudden rise in cases usually resulting from a new infectious agent or a change in an existing agent. Epidemic can follow predictable patterns and these trends are often used to monitor, predict and control the spread of the infection. A typical example of this is “seasonal flu”.
The word pandemic is derived from Greek word ‘pan’ meaning all and ‘demos’ meaning people. The term is used to describe the rapid spread of a transmissible infection or communicable disease worldwide. Once an epidemic becomes global and affects a large percent of the population, it becomes known as Pandemic.
The terms pandemic and epidemic are used to describe the rate and distance of the spread of the disease and not the severity of the disease.
Significant features of Pandemic:
- Affects a wider geographical area, often global.
- Infects a very large number of people.
- Often caused by a new virus or a new star in of a virus that has been dormant for many years.
- Spreads quickly in humans as there is little to no existing immunity.
- It causes high number of deaths.
- Due to the need to control the spread of the disease, there is often social disruption, unrest and economic loss.
Stages of Pandemic:
The WHO has identified six phases that it follows before declaring a pandemic.
- Phase I: A virus is seen I animals but has not been showing infections in humans.
- Phase II: A known animal virus has caused an infection in humans.
- Phase III: Scattered or isolated incidents of cases or small clusters of the disease occurs in humans; possible cases of human to human transmission is seen, but not at a level to cause community level outbreaks.
- Phase IV: Human to human transmission starts at a rate that causes an outbreak in communities.
- Phase V: The spread of the disease between humans is evident in more than one country.
- Phase VI: Community level outbreaks are in at least one additional county other than the one seen in phase V.
Once phase VI is reached preparation is then made for a global pandemic. The most recent example of a pandemic is Covid 19.