Definition
Between 16th and 17th, Pandemic was the first use of this word and referred to “a Pandemick, or Endemick” (Harvey, 1666). Later in 18th (precisely in 1828), the epidemiologist and lexicographer “Noah Webster” listed epidemic and pandemic in her first edition of Webster’s Dictionary, as synonymous terms (Webster, 1828). By the early 19th century, the term epidemic had become the accepted term for what we would call now both an epidemic and a pandemic (Morens, Folkers, & Fauci, 2009).
Epidemic is an outbreak of infectious diseases occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people” (S. S. Harris, 2000). The term “pandemic” is the form of a large epidemic that occur worldwide, or over a very wide area, crossing international boundaries, through human population, and affecting a large number of people (Ghendon, 1994; S. S. Harris, 2000; Last, 2001; Muthu, 2014).
The classical definition, do not take into consideration several factors such as virology and disease severity. Given that seasonal epidemics spread and cross international boundaries by affecting a lot of people, so pandemics can be said to occur annually. However, seasonal epidemics and some diseases are not considered pandemics (Kelly, 2011). As like cancer, is a dangerous disease but is not considered a pandemic because is not infectious and it can kill few persons.
Use of the term “pandemic” by scientists and health agencies often seemed to be at odds for many reasons: i) some scientists supported that declaration of a pandemic need a level of explosive transmissibility, but ii) others experts supported that severity of infection should also be considered (Altman, 2009; Morens et al., 2009).
To understand this concept better, there are eight key features of a pandemic: wide geographic extension, disease movement, novelty, severity, high attack rates and explosiveness, minimal population immunity, infectiousness and contagiousness (Qiu, Rutherford, Mao, & Chu, 2017).