Author: Dr. Ronald St. John
Throughout history there have been outbreaks of infectious diseases. The well-known plague epidemic (Black Death) was a devastating global epidemic of bubonic plague that struck Europe and Asia in the mid-1300s, wiping out an estimated one-third of the population. Disease outbreaks, when large in scope, have been referred to as epidemics. More recently, epidemics that have involved or might involve the global population have been labelled as pandemics.
When does an epidemic become a pandemic? There is no single accepted definition of the term pandemic (ref: Journal of Infectious Diseases, Vol. 200:7, 1 October 2009). Some considerations for labelling an outbreak as a pandemic include outbreaks of diseases:
For purposes of this paper, a pandemic is an epidemic occurring worldwide, or over a very wide area, crossing international boundaries and usually affecting a large number of people.(1)
The worst kinds of pathogens — ones with the highest mortality rates and limited countermeasures — are increasing due to population increases, population density, more global travel, and changing migratory and environmental patterns that result in encroachment upon animal and other populations.
Until some of the basic conditions that favour the expansion of an epidemic to a pandemic are addressed, future pandemics are inevitable. Early detection and coupled with efficient and effective management of a rapid response to contain a disease outbreak at the local level will hopefully minimize the health impact on the global population.
However, much more attention is warranted. Many pandemics are zoonoses — diseases that can be transmitted to humans from animals. Influenza, tuberculosis, bubonic plague, and AIDS (Acquired Immune Deficiency Syndrome) are examples. In fact, today the most promising work on the spread of infectious diseases is being carried out by physicians specializing in epidemiology, veterinary and environmental medicine, working jointly as an inter-disciplinary approach called “One Health.” As wildlife habitats are destroyed to make room for human settlements, and as local climates change with global warming, there are new opportunities for zoonoses to spread. One Health researcher seek to identify these situations quickly, as they emerge worldwide.
In previous times, some virulent diseases had a self-limiting effect; infected people might die quickly -—before they had time to spread their pathogens widely. However, the ease of air travel now makes it possible for infected persons to spread a disease to other continents even before showing symptoms themselves. Thus, the risk of pandemics remains high, despite the spread of advanced medical technology.
Estimates about the probability of a virulent global pandemic are only guesses, but even the most ominous predictions cannot be dismissed. Bill Gates, who is allocating large funds to solving global health problems, sees pandemics as the greatest immediate threat to humanity. He warns that an influenza epidemic alone may kill over 30 million people in six months.(5) Another researcher, David Mannheim, predicts an even more dire possibility. Noting that it is more difficult than ever before to contain an epidemic through local quarantines, he argues that “the evolving nature of the risk means natural pandemics may pose a realistic threat to human civilization.(6).
References for this article can be seen at the Footnotes 3 page on this website (link will open in a new page).