Epidemics and the Global Village

The agitating Ebola emergency has captured headlines. There are some who undoubtedly assume that this kind of epidemic is unusual. However, localized epidemic disease has been a part of the biological system of the planet since the origin of life. Pandemics in which the spread of disease can encompass a continent or the world are just as ancient a process.

We humans have an extensive acquaintance with epidemics and pandemics. Many occurred long before the modern era with its current ease of global travel or any concerns about a changing climate. Our written record of epidemics can be traced as far back as the Ten Plagues of Egypt, which devastated livestock and humans. There are extensive and graphic descriptions of the prior pandemic spread of bubonic plague in Europe and Asia in the Middle Ages that occurred in successive waves.

In more recent history, during the First World War in the fall of 1918, influenza ravaged populations worldwide accounting for an estimated 20-40 million deaths. It moved with astounding speed and at such a pace that more American troops died of influenza than in battle. Although there had been mild outbreaks of influenza in the spring of 1918, few deaths had occurred. However, within a short interval, a new strain of influenza virus emerged and was incredibly lethal, often leading to death within hours of symptoms caused by uncontrollable hemorrhage into the lungs. This pandemic was so sudden and unprecedented, and it exerted its worldwide effect with such fury, a state of panic and chaos was experienced by many communities across the globe. Fatalities were not confined to the very young, elderly and infirm, as is the typical distribution for influenza. Instead, it disproportionately afflicted young adults and the previously healthy. This reversed the normal pattern of mortality so that its impact on the infrastructure of society had critical socioeconomic reverberations.

Now Ebola has raised global alarm. Although the spread of Ebola does not appear to follow the same mode of transmission as influenza, there are certain commonalities among any of the diseases that are currently considered to have the potential for worldwide spread. Both influenza and Ebola are zoonoses, just like the viruses that spread HIV, SARS (Severe Acute Respiratory Syndrome), MERS (Middle East Respiratory Syndrome), or West Nile Virus. A zoonosis is an infection spread from one species to another, from animals to man or from man to another animal. The majority of human pathogens are zoonotic and nearly all the emerging diseases are caused by zoonotic pathogens.