According to the Centers for Disease Control and Prevention, an epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in a population living in a particular area. A disease is considered an epidemic if it spreads over an area (like an entire country) and affects many people simultaneously. Sometimes a disease, especially those that are very contagious, can spread so fast it covers an even larger area, often affecting many countries around the world. An epidemic that spreads over several countries, or continents usually affecting a larger number of people all at the same time is called a pandemic. The World Health Organization (WHO) declares an epidemic officially a pandemic when it spreads globally.
21st Century Pandemics
On March 11, 2020, the (WHO) officially declared the coronavirus outbreak a pandemic after reaching 114 countries and infecting more than 118,000 people worldwide. What started as an outbreak in Wuhan China spread throughout Asia, to neighboring countries like Japan, Taiwan, Korea, and Singapore. Eventually, it reached even countries like Italy and Spain in Europe and then the US among others.
In 2009, the world experienced the first influenza pandemic of the 21st century. The H1N1 pandemic of 2009-2010 was caused by an influenza virus according to the WHO. “While most cases of pandemic H1N1 were mild, globally it is estimated that the 2009 pandemic caused between 100,000 to 400,000 deaths in the first year alone,” the WHO adds.
20th Century Influenza Pandemics
Three influenza pandemics occurred during the 20th century. The most recent was the 1968 flu pandemic also known as the Hong Kong Flu Pandemic of 1968. It lasted until 1969-1970 and was caused by the influenza H3N2 virus. Although it caused fewer deaths compared to other influenza pandemics of the 20th century, the 1968 flu was so contagious it affected 500,000 people in a matter of weeks. It spread rapidly to other countries in South East Asia before reaching the United States, Europe, Africa, and South America among other areas.
Another 20th-century influenza pandemic was the 1957 flu pandemic also known as the Asian Flu of 1957. It was caused by the influenza A subtype virus and was first detected in Guizhou Province of southwestern China. It emerged sometime in February 1957. It killed an estimated 70,000 Americans and up to four million people worldwide.
The worst and deadliest pandemic in history, however, was the Spanish flu of 1918. It infected an estimated 500 million people and killed around 20 to 40 million people worldwide. It was caused by an H1N1 virus with genes of avian origin, according to the CDC. Scientists are still unsure about its origin but the 1918 flu was first diagnosed in parts of Europe, America, and some parts of Asia before it quickly spread throughout the world. It came in waves, the first came in the spring of 1918 and was considered rather mild, the second wave occurred in the summer of the same year and was more lethal—it killed people within 24 hours after first showing symptoms. But it didn’t end there, a third wave occurred in the winter and spring of the following year killing even more people. Many scientists believe that the virus became deadlier and more virulent after it evolved sometime between the first and the second wave.