2023-05-25 17:00:00
Since society is organized in territorial nuclei, diseases have been part of our day to day; above all, the contagious. These can simply pass through our body discreetly or, on the contrary, trigger a pandemic put the whole planet on alert.
A pandemic is considered when the outbreak affects more than one continent and the cases are no longer imported but caused by community transmission.
The last episode with these characteristics was that of SARS-CoV-2, also known as COVID-19: a virus that caused more than 600 million cases in the world and more than 6.8 million dead. However, the death count and the case fatality rate of the coronavirus – which circulates among one 0.8 and 1.1%and rises to 12-16% in those over 80- are far from resembling the figures for these 3 pandemics that even changed the demographic structure of entire continents.
3. Smallpox
Smallpox is caused by a virus called variola, which exclusively affects humans. The disease manifests itself through fever, headaches, vomiting and spots on the skin that later become blisters. Until its eradication in 1977, it was a serious condition that it expanded massively when the conquistadors traveled to America and they infected the local population, which had very low defenses.
Fortunately, a vaccine promoted by Lady Montagu and tested by Edward Jenner in 1796 progressively stopped the advance of this disease. This does not mean that the figures for this pandemic are heartbreaking: around 500 million deaths in the world and one case fatality rate of 30%.
![Mrs](https://www.nationalgeographic.com.es/medio/2023/05/25/vruela_29a21149_230525102904_800x618.jpg)
CC
2. Black fish
This pandemic – which peaked between 1347 y 1353– is considered the most devastating in the history of mankind. It originates from the bacillus Yersinia pestis, which was transmitted by rat fleas (Xenopsylla cheopis).
One of the best-known images of the Black Death is that of the beaked masks. These were used because, due to the lack of knowledge about the disease at the time, it was believed that the infection was caused by the poisoned air. For this reason, to treat patients, doctors placed herbs in the extension of the mask, believing that in this way they created a kind of barrier that protected them from contagion.
It was later found that neither the masks nor the methods were effective. With which, in just 6 years, European demography passed from 80 to 30 million of people, and in the Iberian Peninsula he died between the 60 y 65% Of the inhabitants.
![over black](https://www.nationalgeographic.com.es/medio/2023/05/25/peste-negra_f0db29bd_230525103249_800x1072.jpg)
1. AIDS
Since it was detected in New York and California in 1981, AIDS has killed more than 40.1 million people Worldwide. That is why it continues to be considered a pandemic whose incidence, in addition, is growing back in certain countries.
This disease is caused by the HIV (Human Immunodeficiency Virus) that is not lethal by itself, but by its consequences: the virus attacks the immune system and weakens it, making it easier for the patient to catch other infectious diseases that are fatal in most cases. When the condition evolves to this point is when it is called Acquired immunodeficiency syndrome (SO).
The virus is transmitted through bodily fluids from infected people, such as blood, breast milk, semen, and vaginal secretions. Although AIDS there is no curehealth advances have allowed patients to have a long and dignified life thanks to new treatments, early diagnosis and, above all, prevention strategies and awareness.
However, some areas with fewer opportunities to access medical care continue to fight the disease. In this sense, according to the latest WHO data, it is estimated that by the end of 2021 there were 38.4 million of people living with HIV, and more than two thirds of them were in Africa.
![VIH virus](https://www.nationalgeographic.com.es/medio/2023/05/25/virus-vih_00000000_5f7f2877_230525113546_800x450.jpg)
Photo: Istock
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