The first pandemic on record was the Plague of Justinian in 541. It frequently recurred for another 200 years until it finally disappeared around 750. But pandemics have become a recurring feature of human history for the last 1,500 years—not as persistent as the Plague, but not something that comes along once every couple of centuries either. 

Pandemics result from viruses, bacteria or other pathogens that have mutated and spread quickly through the human population. The word pandemic comes from the Greek pandemic, which means "to spread all at once". As we continue to expand and explore, pathogens have more opportunities to spread, and new technology and travel have made it easier for them to do so. This article will explore some of the most significant pandemics in history, their causes and effects, and what we can do about them moving forward.

The Spanish Influenza Pandemic of 1918-1919

Many different pandemics have occurred throughout history, but the Spanish Flu pandemic of 1918-1919 is the most recent and deadly pandemic we've faced other than COVID-19. It was fatal compared to other pandemics, killing as many as 50 million people worldwide, or 2% of the world's population. Efforts to understand what caused this pandemic are tricky because there are only a few samples of the virus remaining; researchers think it was caused by an H1N1 influenza A virus. 

Typically, Influenza A viruses cause seasonal flu epidemics each year, but occasionally one of the variants will mutate and become more virulent, leading to a pandemic. When the pandemic peaked, the infection rate was about 2.5% of the world's population, meaning almost one in 40 people was infected. It was the deadliest in Asia, where about 10% of the population was infected. In the United States, about 1 in 50 people were infected.

Ebola Virus Pandemic of 2014-2015

The 2014-2015 Ebola pandemic was caused by the Ebola virus, which targets human and non-human primates. It's one of the rarer types of pandemics, but as we expand into more tropical regions, we will encounter it more often. Ebola is one of the rarer types of pandemics that have existed for centuries but has only been known to cause pandemics since the 1970s. It mainly affects sub-Saharan Africa, though it has also spread to Asia and Europe. If a pandemic occurred, the virus would be highly virulent, killing between 50-90% of those infected, though it's unlikely to spread very far beyond Africa because it is not very contagious.

The Hong Kong Flu Pandemic of 1968-1969

The Hong Kong flu pandemic was caused by an influenza A virus and was the first pandemic since the Spanish flu that scientists could study in detail. It was named after the location where it first appeared and was one of the last significant pandemics before the invention of modern antiviral drugs. In 1968, the virus spread from Hong Kong around the globe, infecting an estimated 33 million people and killing about one million. It was particularly fatal among those between the ages of 20 and 40. In the United States, there were about 34,000 deaths from the flu, while the Spanish flu killed over 700,000 people. This dramatic difference in mortality rates primarily resulted from how the pandemic was handled.

Marburg Virus Pandemic of 1967

The Marburg virus pandemic of 1967 was a deadly viral outbreak in the German town of Marburg. Scientists identified the virus behind it in the late 1960s as a newly discovered filovirus called Marburg Virus. Like Ebola, Marburg is a rarer type of pandemic that has existed for centuries but has only been known to cause pandemics since the 1960s. Regarding virulence, Marburg is similar to Ebola, killing 50-90% of those infected. This pandemic was contained in a German laboratory when an infected researcher was put in isolation, and his team of researchers became infected. Although rare, it shows how quickly a pandemic can spread with the right conditions.

Influenza A Virus Pandemic of 1900-1904

Influenza A virus pandemics occur every 10-40 years, and the last major one was in the early 1900s. The virus causes the flu; however, not all flu pandemics are caused by influenza A. 

This pandemic was particularly virulent and is estimated to have killed 3-5% of the world's population, with some estimations as high as 20%. It infected around 1 in 3 people in the United States. This pandemic was a significant contributor to the start of the "modern era of health" because it caused the government in many places to start funding and regulating public health efforts, leading to a more modernized global health system.

Smallpox Pandemic of 1879-1880

The last and deadliest of the smallpox pandemics was in 1879-1880. A few years later, people would completely eradicate the final chapter of a decade-long pandemic that killed millions worldwide. Nevertheless, smallpox was one of the deadliest pandemics ever. Without modern medicine, it killed about 1 in 3 people infected and left many survivors with disfiguring scars. This pandemic was particularly devastating in South Asia, Africa and the Middle East, though it infected people around the globe. The British Raj finally stopped the outbreak by mandating smallpox vaccinations, but there were still many deaths and survivors left disfigured.

Conclusion

Pandemics are one of the gravest threats to humanity on a global scale. As we expand our population and explore new territory, we are increasingly likely to encounter and contract new and deadly viruses. Modern technology and travel have made it easier than ever for viruses to spread. There have been many pandemics throughout history; unfortunately, there are likely to be many more. As we continue to explore, it's essential to remain prepared for pandemics, mainly by clearly understanding the potential threats and how best to respond to them.

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