The word pandemic arises from Greek voices, specifically from the word "πανδημία" which means "gathering of the people", lexically composed of "pan" which means "totality", "dem" which refers to "people", by Hence its etymology gives it the meaning of "the entire town"; other sources state that the entry actually derives from the Greek "pandêmon nosêma" and according to this etymological origin it is a disease that is supposed to affect the entire world. The dictionary of the real Spanish academy exposes the term referring to the field of medicine as an epidemic-type condition that spreads around several countries or, for its part, that affects the majority of the people of a territory or nation.
For 2009, especially in May, the World Health Organization, also known by its acronym WHO, changed the meaning of the term pandemic to describe it as "the worldwide spread of a new disease"; but it should be noted that before this change they defined the word as "Infection by an infectious agent, simultaneous in different countries, with a significant mortality in relation to the proportion of the infected population". The significant change this organization made was to rule out or exclude the "mortality" characteristic.
Throughout history, varieties of pandemics such as tuberculosis and smallpox have emerged. Other registered examples of important pandemics that have marked the history of humanity, often caused by the attempt to domesticate certain animals, are influenza and the aforementioned tuberculosis; others of great importance were the well-known Plague of Athens that occurred during the Peloponnesian War in 430 BC. C., consisted of a typhoid fever that killed a quarter of the Athenian troops and about a quarter of the population during a period of 4 years. Between the years 165 and 180 the Antonine Plague manifested, whose possible cause was smallpox that was leaked in Italy, thanks to the soldiers who returned from the Middle East at that time.
Years later, the first outbreak of the bubonic plague emerged in Egypt, specifically in the year 541 also known as the Plague of Justinian, then spread to Constantinople. The Black Death was another great epidemic that began in the year 1300, killing about 75 million people. A characteristic pandemic that also ended the lives of millions of people, occurred between 1918 and 1919 was the famous Spanish flu.
Recently, or a few years ago, two conditions emerged that are considered pandemics, of which one of them is AIDS, caused by a virus called HIV virus, which began in the African continent and then reached Haiti, then It spread around the world around 1969. The other more recent pandemic is influenza A (H1N1), which is also known as swine flu, discovered in April 2009.
