Causes and management of epidemics and pandemics

Definitions

An epidemic is a contagious, infectious, or viral disease affecting a disproportionate number of persons in a community, region, or population at the same time. A pandemic is a contagious, infectious, or viral disease occurring over a large geographical area or affecting a high proportion of a certain population.

Although both the terms "epidemic" and "pandemic" refer to a disease spreading through a population, a pandemic usually indicates either a larger geographical area or a higher number of people affected, or sometimes both. For example, a disease, such as influenza, may occur in a limited geographical area in many more people than would be expected. If the disease never spreads widely (perhaps only a few other cases appear nationwide), this situation would be an epidemic. However, if the disease spreads into a larger geographical area, for example, across an entire continent, with many more people contracting the disease than would be expected, this episode would then be termed a pandemic.

Another use of the term "pandemic" occurs when the disease affects an inordinate amount of people in a localized population. For example, in some areas of Africa, nearly 100 percent of the population may be infected with the human immunodeficiency virus (HIV), making the situation a pandemic. Generally, a pandemic starts as an epidemic that, because of poor management, negligence, or ignorance, spreads into a larger area or affects a larger percentage of a population.

The application of the words "epidemic" and "pandemic" also depends on what is expected or what has been experienced in the past. For example, the common cold is a virus that is experienced worldwide; however, it is expected and it is known, from experience, that many people contract the virus that leads to the common cold. Even though the cold is a widespread illness, it is not a pandemic, or even an epidemic. Conversely, hantavirus infection, being very rare and neither expected nor experienced by many, becomes epidemic when a few people do become infected.

The words "epidemic" and "pandemic" are also often used in connection with diseases or conditions, such as diabetes or obesity, that are not infectious. In their true scientific senses, epidemic and pandemic refer only to conditions that are contagious or transmittable from one person to another.

Causes

Disease epidemics have been recorded since at least the time of the pharaohs in ancient Egypt, and there are biblical references to plagues and diseases that spread rapidly and decimated human populations. Some of the most striking examples of past epidemics and pandemics include the Black Death, an outbreak of bubonic plague that spread through Europe in the fourteenth century; the smallpox epidemic that affected American Indians at first contact with Europeans; and the Spanish flu, a form of influenza that spread around the world in 1918, killing millions of people in just eighteen months.

Epidemics can be spread by many different means, including by an infectious carrier, contamination, mutation of an infectious agent, human behavior, and environmental change.

Infectious carrier. Sometimes animals carry disease that can spread rapidly through a population. For example, the bubonic plague, which killed an estimated one of every four people in Europe and one of every two people in Venice alone in 1347–48, is thought to have been spread by rats carrying fleas infected with the disease. These fleas easily made the transition from being carried by rats to being carried by people, and through their bites, the fleas spread this disease. Other examples of vectors (organisms that carry disease) are the ticks that carry Lyme disease. Scientists believed the coronavirus disease 2019 (COVID-19), which first began spreading around the world in early 2020, originated in animals and jumped to humans at a live animal market in Wuhan, China, although experts are unsure as to the exact source of the contagion.

It is also possible for a person to be a vector, to carry a disease without becoming or being infected. These carriers can infect others unknowingly. For example, in the early twentieth century case of Mary Mallon (also known as Typhoid Mary), who worked as a cook. Mallon infected more than forty people with typhoid fever. She was immune to typhoid, even though she carried the disease.

Contamination. Contamination of water or food can also be a source of epidemics, such as cholera, which is transmitted through contaminated water. Strange cases of outbreaks can be tied to contamination. For example, an outbreak of cases involving Salmonella bacteria in Minnesota in 1994 was traced back to a particular brand of ice cream. However, Salmonella can be found only in poultry and eggs. Because the ice cream contained neither, the outbreak was puzzling. Further investigation revealed that the ice cream was created with a mix that had been carried by trucks that had previously carried unpasteurized eggs. Another factor was inadequate cleaning, which had contaminated the ice cream mix.

Mutation of an infectious agent. Even when the infectious agent is known, as are the Plasmodium microbes that cause malaria, an agent’s ability to quickly mutate to survive can foil attempts to prevent the spread of disease. These microbes reproduce so rapidly and change genetic material so often that it is difficult for malarial medicine to keep up with the changes. Another problem that continues the spread of malaria is that involving the mosquitoes that carry the disease; they too can quickly mutate and thus survive the application of pesticides, making it difficult to control the population of the infected vectors. Mutated variants of COVID-19 included the highly contagious Delta and Omicron variants that proved to be capable of infecting even those who had been vaccinated against the disease.

Human behavior. Social and political issues also affect how disease is spread. For example, even though many studies have shown that the best way to prevent the spreading of disease is frequent hand-washing, other studies show that people do not always comply with hand-washing recommendations. Another example is the refusal by some parents to vaccinate their children against diseases, even though the benefits of immunization and vaccination far outweigh the risks. Also, sexual contact can transmit certain infectious diseases; some people refuse to practice safer sex, even though doing so has been proven to reduce sexually transmitted diseases (STDs). Lack of education and access to medications are other issues that allow disease to spread.

Another factor in the spread of disease is the introduction of new diseases by nonindigenous populations. For example, American Indians had contact with early settling Europeans, who had gained immunity to but still carried infectious agents, causing American Indians—who had never been exposed to the smallpox virus and thus had no opportunity to develop immunity to it—to contract severe and oftentimes fatal infections from their first exposure. This type of disease transmission still occurs today. With more people traveling the globe, diseases are spread more quickly among populations; for example, severe acute respiratory syndrome (SARS) spread rapidly throughout the world in early 2003 because of the high number of international travelers who were infected.

Political issues also interfere with disease control. US President Woodrow Wilson was roundly criticized for his policies during the influenza outbreak of 1918. Even though many people were dying from influenza, he refused to move resources focused on fighting in World War I to fighting the disease, thus possibly contributing to the spread of the disease and to many more deaths. Poor domestic health services and ineffective response coordination contributed to the epidemic of ebola hemorrhagic fever in several West African countries beginning in 2013; the complications of international politics also delayed efforts to contain the disease. The COVID-19 outbreak showcased a variety of political and societal responses to a pandemic, with nations that displayed unified commitment to combating the spread, such as South Korea, generally facing less severe conditions than nations with more mixed responses, such as the United States.

In 2022 a study conducted by the University of Chicago provided insight into how political ideology in the United States impacted perceptions and responses to COVID-19. Respondents who were described as politically conservative reported to being less worried about the impacts of COVID-19. This group also believed preventative actions against the coronavirus would have a lesser impact. Those identifying as Liberals were more in favor of collective actions. This group was also more likely to engage in preventative measures.

Environmental change. A short-term or long-term change in environmental conditions can contribute to the spread of a disease. An example of environmental change contributing to an epidemic is that of the hantavirus. This virus mysteriously appeared in the American Southwest in 1993, infecting three healthy people and rapidly killing them. The virus then spread through the local population.

Through a series of investigations, epidemiologists discovered that after years of drought, a snowy winter and wet spring had led to an increase in pinion nuts in the area, which, in turn, led to an increase in mice that ate these nuts. The hantavirus can be carried in the feces and urine of these mice. Infection occurred when people cleaned up the mouse droppings, inhaled the virus that was in the contaminated dust, and then passed the virus to other humans. Because of the change in weather, the mice, who had always been in the area, increased in numbers. This led to greater contact with the human population.

Environmental change contributed to the spread of disease among the people of the Lyme, Connecticut, area. People began building homes farther into the woods, which led to more contact with deer that were native to the area. These deer carried ticks that, in turn, carried the bacterium Borrelia burgdorferi. When the ticks began to leave their deer hosts and to infect humans with this bacterium, humans contracted what came to be called Lyme disease. On a larger scale, global warming resulting in milder winters contributed to the spread of ticks, including those carrying Lyme disease, into more and more areas.

Management

Seventeenth-century Dutch scientist Antoni van Leeuwenhoek first looked into his microscope and saw "little animals," thus inspiring scientists such as Robert Koch and Louis Pasteur to study and understand that microbes can cause diseases that can be transmitted from one person to another. Scientists still work at creating antibacterials, antivirals, and vaccines that will prevent people from getting or spreading disease.

However, even with all the medications that are available, there are other hurdles to overcome in managing diseases. Often, medications are too expensive, or, as in cases of war or other civil disruptions, medications do not get to those who need them. Also, a decline in sanitary conditions can lead to outbreaks of disease. Vaccination programs can fail to reach a critical mass of people to keep infectious diseases under control.

Public health agencies also have a role to play in managing disease. Physician John Snow has been credited with pioneering public health action in managing the spread of disease after he investigated the London cholera outbreak in 1854. Cholera was raging through the city, and many still believed that disease was caused by bad air or humours. Snow, however, plotted the cholera outbreak by using a map to pinpoint the cases of the disease. He noticed that many of the people with the disease were getting water from the Thames River through a pump; the river, at the time, was severely polluted with human waste. Even though he made his findings public, some people refused to believe that the polluted water was causing their illnesses. The Reverend Harry Whitehead found Snow’s evidence compelling and worked with Snow to convince city officials to remove the handle of the pump, rendering it unusable. This public health intervention led to a rapid decline in the cases of cholera in the area and to an overhaul and general cleanup of London water sources.

These types of outbreaks still occur, and public health officials resort to seemingly drastic measures to try to control the spread of disease. For example, during a cryptosporidium outbreak in 2007, public health officials in Utah intervened to ensure public safety by asking that children younger than age five, persons wearing a diaper, and persons with diarrhea avoid using public swimming pools. Even after the outbreak subsided, small children were required to wear a swim diaper and plastic pants to help curb the disease.

The larger scale of pandemics, compared to epidemics, means that management efforts generally must also be broader in scope. In some cases major international interventions have targeted localized breakouts or epidemics to prevent the disease from spreading widely. The West African Ebola outbreak of 2013–16 is one example, as the coordinated efforts of governments and groups such as the World Health Organization (WHO) managed to prevent this extremely deadly disease from proliferating out of control around the world by monitoring cases, restricting travel, and imposing quarantines. In contrast, authorities were unable to keep the COVID-19 outbreak localized to its origin point in China, leading the WHO to declare a pandemic in 2020. This put the challenges of global-scale disease management in the spotlight, as different countries implemented different procedures. Some places, such as China, instituted mandatory lockdowns and other strict measures, while other governments, such as in Brazil, downplayed the severity of the crisis. In the United States, management varied from state to state, with governors in the worst affected areas declaring emergencies and restricting travel even as people in other areas of the country remained skeptical about such measures. Nonetheless, by 2023 over one million American deaths had been attributed to COVID-19 with global fatalities nearing seven million persons.

In any infectious disease outbreak, experts emphasize the importance of "flattening the curve" of new cases. This refers to slowing the spread of the disease, which can not only help lower the total number of infections but also help prevent medical facilities from being overwhelmed by a surge in patients. The policy of "social distancing" that was encouraged around the world during the COVID-19 pandemic illustrates this management strategy. By limiting social interaction, people can lower their chances of infection and of infecting others. Other preventative measures utilized during the COVID-19 pandemic included the often-times mandatory wearing of masks, and the prohibition of gatherings such as for sporting events. A number of treatments have become available for COVID-19. Most are intended for use by adults, although children typically older than 12 can also be deemed eligible. These include antiviral drugs such as Paxlovid, Remdesivir, and Molnupiravir.

Impact

Epidemics have raged through populations since the beginning of human existence, and the future will be no different. The ability of infectious agents to propagate and mutate far outstrips the human immune system’s ability to adapt to and fight contagious diseases. In addition to the lives lost due to illness, epidemics and pandemics can have huge societal and economic consequences. For example, the Black Death deeply influenced European culture in the Middle Ages, while the COVID-19 pandemic led to a drastic stock market decline and spike in unemployment as well as more long-term consequences, such as a shift in the ways many people worked, from working in offices to working remotely.

Fear and ignorance of how disease is transmitted can also have a significant impact. For example, misunderstandings of how a particular disease is transmitted led to fear of touching persons with AIDS at the beginning of the AIDS pandemic. More recently, misunderstandings of how the H1N1 virus is transmitted led to the slaughter of pigs in certain countries. Neither of these actions impacted the infection rates of these diseases. On the other hand, unfounded skepticism in some circles about the seriousness and even the very existence of COVID-19—a problem compounded by mixed messaging from the highest levels of the US government—contributed to the spread of the disease in some areas as people ignored public health guidelines.

The keys to preventing epidemics and pandemics include understanding how a particular disease is transmitted and spread through a population; using public health pathways to provide and act upon scientifically proven information, both in controlling a disease and preventing it in the first place; and educating the public on good health practices, both socially and physically.

Bibliography

Baker, Robert. Epidemic: The Past, Present, and Future of the Diseases that Made Us. London: Vision, 2008. Print.

Barry, John M. The Great Influenza: The Story of the Deadliest Pandemic in History. New York: Penguin Books, 2005. Print.

Bisen, Prakash S., and Ruchika Raghuvanshi. Emerging Epidemics: Management and Control. Hoboken: Wiley, 2013. Print.

Caceres, Vanessa. "What's the Difference Between and Epidemic and a Pandemic?" US News & World Report, 13 Mar. 2020, https://health.usnews.com/conditions/articles/whats-the-difference-between-an-epidemic-and-pandemic. Accessed 8 Apr. 2020.

“CDC Museum COVID-19 Timeline.” Centers for Disease Control and Prevention, 16 Aug. 2022, www.cdc.gov/museum/timeline/covid19. Accessed 7 Mar. 2023.

DeSalle, Rob, ed. Epidemic! The World of Infectious Disease. New York: New Press, 2000. Print.

"Disease Outbreaks." World Health Organization, 2020, www.who.int/emergencies/diseases/en/. Accessed 8 Apr. 2020.

Doherty, P. C. Pandemics. Oxford: Oxford UP, 2013. Print.

Giles-Vernick, Tamara, and Susan Craddock, eds. Influenza and Public Health: Learning from Past Pandemics. London: Earthscan, 2010. Print.

Hardt, Mark D. History of Infectious Disease Pandemics in Urban Societies. Lanham: Lexington, 2015. Print.

Herring, Ann, and Alan C. Swedlund. Plagues and Epidemics: Infected Spaces Past and Present. New York: Berg, 2010. Print.

Johnson, Steven. The Ghost Map: The Story of London’s Most Terrifying Epidemic, and How It Changed Science, Cities, and the Modern World. New York: Riverhead Books, 2007. Print.

Maxmen, Amy. "Wuhan Market Was Epicentre of Pandemic's Start, Studies Suggest." Nature, 27 Feb. 2022, www.nature.com/articles/d41586-022-00584-8. Accessed 15 Apr. 2022.

McKenna, Maryn. Beating Back the Devil: On the Front Lines with the Disease Detectives of the Epidemic Intelligence Service. New York: Free Press, 2008. Print.

Moore, Peter. Little Book of Pandemics. New York: Harper, 2008. Print.

"Outbreaks, Epidemics and Pandemics—What You Need To Know." Association for Professional in Infection Control and Epidemiology, 2020, apic.org/monthly‗alerts/outbreaks-epidemics-and-pandemics-what-you-need-to-know. Accessed 8 Apr. 2020.

Pendergrast, Mark. Inside the Outbreaks: The Elite Medical Detectives of the Epidemic Intelligence Service. Boston: Houghton Mifflin Harcourt, 2010. Print.

“Preventing the Spread of the Coronavirus.” Harvard Health Publishing, 28 Feb. 2022, www.health.harvard.edu/diseases-and-conditions/preventing-the-spread-of-the-coronavirus. Accessed 7 Mar. 2023.

Specktor, Brandon. "Coronavirus: What Is 'Flattening the Curve,' and Will It Work?" LiveScience, 16 Mar. 2020,www.livescience.com/coronavirus-flatten-the-curve.html. Accessed 8 Apr. 2020.

”Total Number of U.S. COVID-19 Cases and Deaths February 22, 2023.” Statista, 27 Feb. 2023, www.statista.com/statistics/1101932/coronavirus-covid19-cases-and-deaths-number-us-americans. Accessed 7 Mar. 2023.