A Review of Global Epidemics

Transmission electron micrograph of the H1N1, or swine flu, virus that was rampant in 2009. Swine flu was one of the world’s most recent epidemics.

Transmission electron micrograph of the H1N1, or swine flu, virus that was rampant in 2009. Swine flu was one of the world’s most recent epidemics.


The word epidemic comes from the Greek words “epi” and “demos,” which translate to “upon people.” Epidemics are commonly referred to as outbreaks; however, the general public usually associates outbreaks with smaller, more contained cases. In contrast, “pandemic” describes a large and often devastating epidemic. The field of epidemiology is dedicated to the study of epidemics and their causes.

Epidemics have plagued mankind, killing millions of people over thousands of years. In the process, they have reformed society as we know it, playing a pivotal role in changing and developing the sciences, religion, and governments around the world.


Epidemics have left a significant mark on human history. Mankind has progressed from the nomadic hunter-gatherers to the vaccinated epidemiologist through lessons learned from past pandemics. The following endemic diseases are a few of the most significant in human history:

Bubonic Plague

The most devastating recorded pandemic was the bubonic plague, also known as the “Black Death.” The bubonic plague is a bacterial disease caused by Yersinia pestis. It typically affects wild rodents and is spread by fleas (1). If the bacteria enter the lungs, the affected individual will develop the pneumonic plague, a severe type of lung infection, which transmits through coughing. Symptoms do not arise for seven to 10 days after infection, but individuals can die within 24 hours of developing the plague.

Patients were nearly incurable during the Middle Ages. Fortunately, the bubonic plague can now be treated with antibiotics, but the mortality rate of patients who develop the plaque remains high. The telltale sign of the plague were buboes, or swelling lymph nodes, in the groin, neck, and armpits that oozed pus and bled when irritated (1).

The plague is estimated to have killed between 75 to 200 million people in Europe over a five-year span from 1347 to 1352. Conservative estimates state that roughly one-third of the European population was decimated by the bubonic plague. More liberal estimates place that number around 60 percent. Given these statistics, it took another 150 years for Europe to replenish its population (1).


The viruses Variola major and Variola minor cause smallpox. While the former has historically killed 30 percent of all the infected, the latter has killed less than one percent (2).

Smallpox is typically spread through the air or through contact with mucus or bodily fluids of a diseased person. The disease exhibits four different types: ordinary, modified, malignant, and hemorrhagic. Each type represents fluctuations in the presentation of the virus, with some more serious than others. Ordinary type smallpox represents approximately 90 percent of unvaccinated cases (2).

After an incubation period of approximately 12 days, initial common symptoms include high fever, muscle aches, nausea, and vomiting. The symbolic symptom of smallpox is the growth of a maculopapular rash, a thick red rash with small raised bumps, which soon developed into fluid-filled blisters. Modified type smallpox is characterized by markedly repressed symptoms, which rarely result in death. Malignant type smallpox is nearly always fatal and represents five to 10 percent of cases. Lastly, hemorrhagic smallpox is represented by hemorrhaging under the skin, giving it the name “black pox.” It is also often fatal (2).

Although smallpox was a reoccurring epidemic that struck several continents, the more significant outbreaks occured in the Americas. From the 16th century until its eradication in the mid-20th century, smallpox ravaged the American native and colonial population. In particular, it played a significant role in destroying the native civilizations of South and Central America. During the late 16th century, explorers from Europe brought smallpox to the natives, killing an estimated 90 percent of the local population (2).

Over two centuries later, the first major breakthrough in epidemic containment occurred when Edward Jenner, an English physician, vaccinated a young boy with cowpox, a relative of smallpox. and then inoculated the boy with smallpox. The world’s first vaccination, derived from Latin vacca or cow, represented the first step of many to combat smallpox and epidemics in general. After a successful worldwide vaccination program, smallpox was completely eradicated in the United States in 1949 and worldwide in 1977, lending continued hope for the eradication of other epidemics and diseases (2).

Spanish Influenza

The Spanish Influenza epidemic of 1918 was a particularly devastating incidence of an influenza pandemic. Influenza, more commonly known as the flu, is caused by RNA viruses. Common symptoms include nausea, vomiting, fatigue, headache, chills, fever, and sore throat. Influenza is a seasonal disease typically transmitted via air pathways and through nasal secretions. It targets individuals without existing antibodies (3).

The flu is typically considered a relatively mild disease; however, extremely virulent forms can have devastating effects. In particular, the Spanish flu killed between 25 and 50 million people between 1918 and 1920, a range of three to five percent of the entire world population. The virus was particularly devastating in that it primarily affected healthy younger adults rather than children and the elderly, wh are more often targeted by influenza (3)

The flu, named for its extensive media coverage in war-neutral Spain, coincided with World War I. The mortality rate of this disease was estimated to be between two and 20 percent, proving that even the flu could grow to be catastrophic.


Poliomyelitis, also known as polio, is a viral disease known for causing acute paralysis of the legs. Polio is an infectious disease transferred through oral contact with fecal matter, either through polluted water or other methods. The virus does not exhibit symptoms in all who are infected, but, for the unfortunate few, it can enter the central nervous system and destroy motor neurons, which leads to paralysis and muscle weakness (3).

At the onset of the 20th century, polio began to surface in Europe and the United States, proving to be an epidemic that paralyzed thousands of adults and children. Consequently, a race to eliminate polio began, culminating in the invention of the polio vaccine in the 1950s (4).

The endemic disease eradication effort again showed promise; polio was declared eradicated in the United States in 1994. While polio has not completely disappeared, many organizations such as the World Health Organization (WHO), Rotary International, and UNICEF are confident that the virus will be vanquished in the near future, as it only exists in fewer than 20 countries today (4).


Over the past few decades, the field of epidemiology has expanded rapidly. An increased understanding of biological mechanisms for infectious diseases, coupled with a general surge in government and public interest in public health, has increased research on the causes and containment of epidemics. Surveillance of infectious disease epidemics has also increased (2).

Recent discoveries of vaccines and advancements in the field of epidemiology have rendered many of yesterday’s dangerous diseases harmless. Consider that AIDS, one of the largest pandemics of modern time, currently affects less than one percent of the world population, whereas the bubonic plague, uncontrollable at the time, was responsible for killing up to one third of the world’s population.

Modern organizations and government agencies, such as the World Health Organization and the Centers for Disease Control and Prevention, limit the spread of epidemics, educate the public about current diseases, and continue to research new solutions to these endemic issues. Additionally, the World Health Organization has implemented guidelines, classifications, and preventative measures for pandemics such as the recent Avian Flu and Swine Flu. Although no catastrophic pandemics have cleaved through the human race today, recently several epidemics have made headlines.


Acquired immunodeficiency syndrome (AIDS) is a disease caused by infection with human immunodeficiency virus (HIV). HIV is a retrovirus that, when contracted, causes symptoms of fever, inflammation, and a maculopapular rash. Eventually, HIV will progress to AIDS when T-cells, an important type of white blood cell, count drops below a certain level. AIDS patients display symptoms of cachexia, or muscle wasting, pneumocystis pneumonia, and an increased risk of developing certain cancers.

HIV is spread by unprotected sexual intercourse, exposure to bodily fluids, or via mother to child during pregnancy, delivery, or breastfeeding. AIDS came to the United States in 1976 and was first discovered in 1981. Since then, it has killed around 30 million people worldwide. Currently, 34 million people live with either HIV or AIDS worldwide.

Swine Flu

Swine flu, also known as Influenza A H1N1, is a strain of influenza that originates from pigs. The disease mirrored the behavior of the seasonal flu except that no vaccine for it existed. The major cause for concern lay in the virus’s potential for mutation—it could become a disease as lethal and widespread as the Spanish Influenza. Mutations that increase transfer rate or severity could prove devastating, especially in undeveloped countries. By May of 2010, the World Health Organizaiton declared the pandemic to be over. The estimated death total worldwide was between 151,700 and 575,400 people (4).


Severe acute respiratory syndrome, or “SARS,” is a respiratory disease caused by the coronavirus. This virus induces symptoms of fever, muscle pain, coughing, and sore throat. Although the SARS virus ultimately was not a pandemic due to the size and scale of the disease, it had the potential to become one. SARS was responsible for 775 deaths worldwide, a paltry number at first glance but far more significant after factoring in the 9.6% fatality rate. No vaccine has been discovered, but research is underway (4).


Several factors play a role in determining whether humans will be able to overcome the next major pandemic.

Antibiotic and Antiviral Resistance

The “plague” has resurfaced several times over the last millennium. There is always a possibility that it could develop drug resistance and once again become an extreme health risk. In fact, the Chief Medical Officer of the United Kingdom, Sally Davies, stated, “Antimicrobial resistance is a ticking time bomb not only for the UK but also for the world”, adding that “we need to work with everyone to ensure the apocalyptic scenario of widespread antimicrobial resistance does not become a reality” (5). Widespread antibiotic and antiviral resistance is an obstacle for eliminating many infectious diseases. Continued evolution would complicate development and further slow down scientists, who are already hindered by a declining budget and decreased urgency (5).

Biological Warfare

Throughout history, biological warfare has been a significant threat to global prosperity. Professor Andrew Eaton, a researcher of infectious diseases at the University of Warwick, stated, “When people see the fatalities that can occur within a disease outbreak they understand the damage that can be caused to the enemy” (6). During the French and Indian War, smallpox was used as an agent of biological warfare in order to inoculate the natives (6).

Smallpox has since been eradicated, but two known frozen cultures have been preserved—one in the US and one in Russia. If they were to fall into the wrong hands, disaster could ensue. Furthermore, if other common diseases such as malaria or influenza were modified in a scientific setting, scientists could effectively mold the perfect pandemic and the ideal biological weapon (6).

Smallpox and other known diseases are not the only possibly terrifying biological weapons. New diseases are continuously being discovered, and each could be utilized as a weapon of mass destruction (7).

Eradication of Additional Diseases

Although many significant diseases have been safely shelved away in most parts of the world, a good number of other infectious diseases continue to cause chaos around the world. According to Marc Strassburg, in order to decide the next disease to be eradicated as a priority, the following factors must be discussed: “(1) the degree of understanding of the natural history of the disease; (2) types of appropriate control measures available; (3) mortality produced by the disease; (4) morbidity, including suffering and disability; (5) availability of adequate funding; (6) the cost-benefit of such an eradication effort; and (7) the probability of success within a given time period” (7).

He goes on to state that the reason malaria, one of the most morbid diseases of modern day, has not been eliminated is due to the potential budget. More than one billion dollars would be needed to establish the first year of a vaccination program. Other diseases also continue to exist because of limited funding (7)


Scientific progress bodes well for the eradication of current pandemics as well as protection against those in the future. Nevertheless, continuous scientific advances and innovation will be required to combat a constantly evolving array of infectious diseases.


Contact Harrison Han at



1. Plague. Available at http://www.who.int/topics/plague/en/ (31 March 2013).

2. Smallpox Disease Overview. Available at http://www.bt.cdc.gov/agent/smallpox/overview/disease-facts.asp (31 March 2013).

3. R. A. Goodman, Epidemic, AccessScience@McGraw-Hill (2012). Available at: http://www.accessscience.com. (25 March 2013).

4. http://www.cdc.gov/flu/spotlights/pandemic-global-estimates.htm. (9 April 2013).

5. N. Stafford, Antibiotic Resistance a ‘ticking time bomb’ (13 March 2013).  Available at http://www.rsc.org/chemistryworld/2013/03/antibiotic-resistance-ticking-time-bomb (31 March 2013).

6. P. Jenkins, Biological Warfare. Available at http://www2.warwick.ac.uk/knowledge/themes/terror/biologicalwarfare/. (31 March 2013).

7. M. A. Strassburg, The global eradication of smallpox, American Journal of Infection Control, 10, 2, (May 1982)

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