A pandemic is an outbreak of an infectious disease that affects a large proportion of the population in multiple countries or worldwide. Human populations have been affected by pandemics since ancient times. These include widespread outbreaks of plague, cholera, influenza and, more recently, HIV/AIDS and COVID-19. In order to slow or stop the spread of disease, governments implement public health measures that include testing, isolation and quarantine. In Canada, public health agencies at the federal, provincial and municipal levels play an important role in monitoring disease, advising governments and communicating to the public.
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What Is a Pandemic?
A pandemic is an outbreak of a disease that causes serious illness or death among a high proportion of the population in multiple countries or continents. Pandemics are global events caused by bacteria and viruses that are highly contagious in human populations. It is the most widespread state of a disease.
Levels of Disease
Sporadic: A sporadic disease appears occasionally. It is not usually concentrated in a specific geographic area.
Endemic: This refers to the constant presence or usual prevalence (or frequency) of a disease within a certain area.
Epidemic: An increase in the number of cases of a disease, above what is usual for a certain area. This increase is often sudden.
Pandemic: An epidemic that has spread to other countries or continents.
Main Features of a Pandemic
Pandemics can spread rapidly across the globe, often within less than a year, and an estimated one-quarter of the human population contracts the illness. Pandemics typically start abruptly, peak rapidly and subside fairly quickly. However, they also tend to recur in waves that begin simultaneously in different regions. These waves, which may include second and third waves, can cause even more serious disease.
The first pandemic in recorded history is the plague, an infectious disease caused by bacteria called Yersinia pestis, which are found in rodents, especially rats, and in the fleas that feed on them. Plagues have occurred since ancient times and continue to affect communities in Africa to this day. The most well-known plague, though, was the pandemic that began in the early 14th century in Asia and was subsequently introduced into Europe. This bubonic plague, known as the “Black Death,” eventually killed more than one-third of the European population. (Bubonic plague is highly contagious and characterized by fever, delirium and swollen lymph nodes, called buboes.) The Black Death was transmitted to humans from rodents via fleas. Fleas served as vectors, or carriers of the infection, for the disease in humans. At the time, however, no one understood how the disease was transmitted, and no one knew how to prevent or treat it. It would be centuries before researchers discovered the role of bacteria in causing disease. Effective antibiotics were not developed until the 20th century. Governments therefore responded to the 14th century plague by isolating victims and developing and implementing a quarantine system.
Plague epidemics continued throughout the early modern period, affecting countries around the world, including those in Europe. For example, London, England, suffered nearly 40 outbreaks between the 15th and 17th centuries. In 1665, around 100,000 Londoners (about 20 per cent of the population) died within seven months in the city’s last plague outbreak.
As Europeans began immigrating to North America in large numbers around this time, colonial governments became worried that they might also bring plague — as well as other diseases like typhus fever and smallpox. In response, they inspected ships before passengers were landed on shore. This became more routine in New France starting in 1710. In 1721, the colonial government passed a quarantine act in response to fears that the plague would be brought over from Europe. A more comprehensive law followed in 1795: the Quarantine Act of Lower Canada. This legislation became a template for colonial governments in British North America as they developed their own laws. (See also Quarantine Act.)
Cholera Pandemics (19th Century)
Cholera first reached Canada in 1832, brought by immigrants from Britain. This was part of the second cholera pandemic, which began in the 1820s in India and spread to Central Asia, the Middle East, Europe and North America. (The first cholera pandemic began in 1817 but didn’t spread as far.)
Cholera was feared because it was deadly, and no one understood at first how it spread or how to treat it. The main public health response was quarantine. Grosse Île, near Quebec City, became a quarantine station in 1832 and all ships stopped there for inspection. However, apparently healthy (but infectious) people passed inspection and brought the disease with them. Human wastes from the ships also infected the St. Lawrence River. As a result, the disease spread to Montreal and Upper Canada. By the time the epidemic had ended, about 10 per cent of the population of Quebec City and almost 15 per cent of the Montreal population had died of cholera. Cholera epidemics also broke out in 1834, 1849, 1851 and 1854 in Canada, killing at least 20,000 people in total.
In 1854, British physician John Snow proved that cholera was a waterborne disease. This eventually led to improved sanitation and water supply systems, which in turn helped prevent the disease’s spread. However, cholera still affects communities around the world.
Influenza Pandemic of 1918–20
The influenza pandemic commonly known as the Spanish flu developed at the end of the First World War. Its origins are debated. The first outbreaks of the disease occurred in the spring of 1918. The infection travelled back and forth between Europe and North America on the ships carrying troops fighting in the First World War. These troops then introduced the disease into Asia and Africa. The Spanish flu eventually killed about 50 million people worldwide (although estimates range from 20 to 100 million). In Canada, about 50,000 people died, and all parts of the country were affected. The timing of this flu’s development was critical to the eventual success of the virus because there were many people travelling from one part of the world to another. The 1918 flu is widely recognized as the most devastating pandemic in history.
Did you know?
The name “Spanish flu” emerged as the result of media censorship by the military in Allied countries during the war. These countries suppressed the reporting of the viral infection and death of soldiers. However, in Spain, which was neutral during the First World War, the media widely reported the high incidence of death from the illness. The name of the virus became associated with Spain as a result.
H1N1 or Swin Flu (2009)
The H1N1 flu virus was first reported in Mexico in February 2009. Initially referred to as the “swine flu,” the virus had never been seen before in either animals or humans. However, it was thought to be most closely related to influenza viruses found in pigs in North America and Eurasia.
On 26 April 2009, Canada’s Public Health Agency reported the country’s first case of H1N1. By 11 June 2009, 74 countries had confirmed cases of the virus, and the WHO announced a pandemic. Unlike the seasonal flu common during the winter, many Canadians contracted H1N1 during the summer months. A second wave of the virus followed in the winter of 2009. However, by January 2010 the Public Health Agency had begun to scale back its response to the pandemic. By July 2010, more than 200 countries or territories had reported cases of the virus. More than 18,000 people died of H1N1 worldwide. This included 428 Canadians. (See also Influenza.)
The HIV/AIDS pandemic does not fit the pattern of most worldwide outbreaks. The disease is transmitted primarily through sexual intercourse or the sharing of drug injection equipment with infected persons. It has also affected less than one-quarter of the global population. Despite this, HIV/AIDS is widely considered a pandemic, as millions of people worldwide have been affected by the disease.
The first cases of AIDS were reported in the United States in 1981. Canada reported its first case in March 1982. By the end of 1990, more than 307,000 AIDS cases had been reported worldwide. However, the World Health Organization (WHO) estimated that the total number was closer to one million and that eight to ten million were infected by HIV, the virus responsible for the disease. In 2018, an estimated 37.9 million people were living with HIV worldwide. According to the WHO in 2018, 75 million people have been infected by HIV since the pandemic began. Of these, about 32 million have died. In the 21st century, low-income countries, particularly those in the WHO African region, have suffered disproportionately from the disease. The availability of HIV testing, counselling and antiretroviral therapy plays an important role in the prevention and control of HIV/AIDS.
In Canada, the number of HIV-infected patients increased in the 1980s, slowed down in the mid-1990s, but then rose again toward the end of that decade. Since 2014, the number of new cases of HIV has risen every year in Canada. By the end of 2016, it was estimated that more than 63,000 Canadians were living with HIV. Experts have suggested that the increase may be the result of new HIV infections, increased HIV testing and reporting, and an increase in the number of HIV-infected people migrating to Canada. In addition, more effective treatment options have resulted in fewer deaths due to the disease. In total, almost 25,000 Canadians have died of AIDS and related causes since the pandemic began.
In December 2019, an outbreak of a newly discovered coronavirus was reported in Wuhan, China. Coronaviruses are a family of zoonotic viruses. Zoonotic viruses are those that can be transmitted from animals to humans. This group of viruses can cause a range of respiratory ailments, including the common cold. Symptoms of the disease, which was named COVID-19, are similar to a cold or flu and may include cough, fever, difficulty breathing and, in more severe cases, pneumonia. On 11 March 2020, the WHO declared a pandemic, as 118,000 cases of the disease had been reported in 114 countries, killing 4,291 people. As of early March 2023, there were more than 758 million confirmed cases of COVID-19 and 6.87 million deaths worldwide. During the same period, there were approximately 4.6 million confirmed cases and 51,447 deaths reported in Canada.
Epidemiology and Prevention
Epidemiology is the study of disease in human populations, including the causes, distribution patterns and control of disease. It is an important aspect of public health research across the world. Canada and many other countries cooperate with the WHO to research potential pandemics and the transmission of diseases from one species to another.
The outbreaks of severe acute respiratory syndrome (SARS) and COVID-19 in the early 21st century renewed interest in the 1918 flu. These viral infections originated from mutated animal viruses. Animal viruses are not usually contagious in humans, and a virus must undergo certain changes in genes, or mutations, to become infectious. Scientists do not understand the exact mutations involved, but research into historical diseases such as the 1918 flu may help develop new theories and potential treatments.
Canada began planning for pandemic influenza viruses in 1983. The federal, provincial and territorial health agencies work together to plan a coordinated response to a potential pandemic. Immunization is an essential aspect of preparation for any viral infection. Coordination between all levels of government is key to running an effective vaccination program that can help prevent future pandemics.
Bacteria - Bacteria are microscopic single-celled organisms that can cause serious infectious diseases.
Epidemic - A widespread outbreak of an infectious disease in a population at a particular time.
Pandemic - An outbreak of an infectious disease, usually caused by a new virus or bacterium, or a novel strain, that affects a large proportion of the population in multiple countries or worldwide.
Public Health - Health services, usually preventative in approach, provided by a government to improve the health of citizens on a population level.
Quarantine - The separation of an individual, or a group of people, from a surrounding population and the restriction of their movement to prevent the introduction and spread of a disease.
Vaccine - A preparation made from killed or weakened bacteria or virus, or their specific antigens, that stimulates the body to develop immunity to that same bacteria or virus.
Virus - An organism, too small to be seen with a typical microscope, that can multiply inside the cells of its host and usually causes disease.
Zoonotic Virus - A virus that can be transmitted from animals to humans.