What is Pandemic? Pandemic is an epidemic occurring on a scale that crosses International Boundaries, usually affecting a large number of people. Pandemics can also occur in important agricultural organisms (livestock, crop plants, fish, tree species) or in other organisms. A disease or condition is not a pandemic merely because it is widespread or kills many people; it must also be infectious.
What is the difference between a Pandemic and an Epidemic? An Epidemic is an outbreak of disease that spreads quickly and affects many individuals at the same time. A Pandemic is a kind of Epidemic; one which has spread across a wider Geographic range than an Epidemic, and which has affected a significant portion of the population.
List of Deadly Outbreaks of the last 100 Years : Plague, smallpox, cholera, bubonic and influenza are some of the most brutal killers in human history. And Deadly Outbreaks of these diseases across international borders, are properly defined as pandemic, especially smallpox, which throughout history, has killed between 300-500 million people in its 12,000 year existence.

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A Timeline of Historical Pandemics
Disease and illnesses have plagued humanity since the earliest days, our mortal flaw. However, it was not until the marked shift to agrarian communities that the scale and spread of these diseases increased dramatically.
Across the board exchange made new open doors for human and creature communications that accelerated such pandemics. Jungle fever, tuberculosis, infection, flu, smallpox, and others originally showed up during these early years.
The more humanized people became – with bigger urban communities, progressively fascinating exchange courses, and expanded contact with various populaces of individuals, creatures, and biological systems – the almost certain pandemics would happen.
Here are a portion of the significant pandemics that have happened after some time:

Spanish flu: The Spanish flu (also known as the 1918 flu pandemic) was an unusually deadly influenza pandemic. Lasting from January 1918 to December 1920, it infected 500 million people—about a quarter of the world's population at the time World War I.
Asian flu: A pandemic of influenza A (H2N2) in 1957-58. First identified in China in late February 1957, the Asian flu spread to the United States by June 1957 where it caused about 70,000 deaths. Also known as Asian influenza.
Hong Kong flu: The Hong Kong flu was a category 2 flu pandemic whose outbreak in 1968 and 1969 killed an estimated one million people all over the world.
HIV/AIDS: HIV (human immunodeficiency virus) is a virus that attacks cells that help the body fight infection, making a person more vulnerable to other infections and diseases. If left untreated, HIV can lead to the disease AIDS (acquired immunodeficiency syndrome)
Swine Flu: A human respiratory infection caused by an influenza strain that started in pigs. Swine flu was first recognised in the 1919 pandemic and still circulates as a seasonal flu virus. Swine flu is caused by the H1N1 virus strain, which started in pigs.
SARS : SARS appeared in 2002 in China. It spread worldwide within a few months, although it was quickly contained. SARS is a virus transmitted through droplets that enter the air when someone with the disease coughs, sneezes or talks. No known transmission has occurred since 2004.
Ebola: Ebola is a rare but deadly virus that causes fever, body aches, and diarrhea, and sometimes bleeding inside and outside the body. As the virus spreads through the body, it damages the immune system and organs. Ultimately, it causes levels of blood-clotting cells to drop
MERS: Middle East respiratory syndrome-related coronavirus, or EMC/2012, is a species of coronavirus which infects humans, bats, and camels. The infecting virus is an enveloped, positive-sense, single-stranded RNA virus which enters its host cell by binding to the DPP4 receptor.
COVID-19: Coronavirus disease (COVID-19) is an infectious disease caused by a new virus.
The disease causes respiratory illness (like the flu) with symptoms such as a cough, fever, and in more severe cases, difficulty breathing. You can protect yourself by washing your hands frequently, avoiding touching your face, and avoiding close contact (1 meter or 3 feet) with people who are unwell.
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