As the recent emergence of a new coronavirus in China sends ripples across the world, with medical personnel striving to contain the pathogen and to gauge the full extent of the danger it poses, it seems a good time to reflect that humanity has had to face far greater viral threats throughout its history.
Probably one of the most (if not the most) infamous pathogens on the planet, the plague reaped its deadly toll in most corners of the world on more than a single occasion, with the word itself becoming synonymous with disease and death.
The epidemic known as the Black Death wiped out between 30 and 60 percent of Europe's population in the 14th century, while a plague pandemic that emerged from the Chinese province of Yunnan in 19th century killed about 12 million people in India and China.
The deadly influenza pandemic that hit the world in 1918, colloquially known as the 'Spanish flu', infected about half a billion people and killed up to 50 million (a number almost as big as the current population of England).
The disease's spread was further exacerbated by the ongoing World War, and it exhibited an unusually high mortality rate among young adults who are normally less susceptible to influenza.
One of the oldest diseases in history which dates back to the prehistoric times, smallpox is estimated to have claimed between 300 million and 500 million lives in the 20th century alone.
In 1979, however, the WHO certified the global eradication of smallpox which was made possible thanks to successful vaccination campaigns in the 19th and 20th centuries.
The Human Immunodeficiency Virus is an insidious virus that wreaks havoc on a person's immune system, thus making them vulnerable to other infections and diseases.
According to WHO estimates, 75 million people have been infected with the HIV virus globally and about 32 million people have died of it, with about 37.9 million people living with HIV at the end of 2018.
A highly contagious infectious disease, measles is estimated to affect about 20 million people worldwide., causing some 110,000 deaths in 2017.
Despite being fairly uncommon in the countries that practice routine child vaccination (as the measles vaccine is very effective in preventing the disease), this pathogen made headlines last year as the number of measles cases in the United States skyrocketed.