What are the most dangerous viruses in the history of mankind?

The history of humanity is marked by pandemics that have claimed the lives of millions of people around the world.

Among these diseases, those caused by viruses have had a significant impact, mainly due to their high rate of mutation and spread.

The history of humanity is marked by pandemics that have claimed the lives of millions of people around the world. Among these diseases, those caused by  viruses have had a significant impact, mainly due to their high mutation rate and the fact that they can spread easily.

A very recent example can be found in the covid-19 pandemic , during which more than 700 million people around the world have been infected and more than 15 million have lost their lives . However, although this has been a highly mediated pandemic, it is not the first time that a virus has threatened humanity.

On occasions, viruses with a high lethality have also appeared, which, however, have not had such a great impact on society due to their low rate of spread. Even so, its seriousness means that taking measures to limit its contagion continues to be relevant.

This is important in today’s world, where factors such as globalization, climate change, and deforestation can contribute to increased contact between species that do not normally interact. This increases the likelihood of virus transmission between species.

These are some of the deadliest and most dangerous viruses that have hit mankind.

The smallpox virus

The smallpox virus is the causative agent of smallpox, an infectious disease that has affected humans for thousands of years. It is characterized by the appearance of painful skin rashes all over the body and by causing the death of approximately one third of infected people.

Fortunately, smallpox was eradicated in 1980 thanks mainly to vaccination. It is the first (and so far the only) human disease to be eradicated.

The eradication of smallpox is an unprecedented achievement in human history and a good example of what can be achieved with coordinated global efforts.

However, despite the fact that the disease has been eradicated, there is a possibility that the virus could reappear in the future or even be used as a bioweapon. Therefore, samples of the virus still exist in high-security laboratories so that researchers can continue to study it and develop new vaccines and treatments.


Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is a highly contagious virus that causes the disease known as covid-19 . This virus was first identified in Wuhan, China, at the end of 2019 and has become a global pandemic that has affected millions of people around the world. So far the virus has infected more than 700 million people and killed more than 15 million.

Although most people infected with covid-19 recover without the need for special treatment, the disease can be severe and life-threatening in older people and people in risk groups. For example, those with pre-existing medical conditions.

Today we have several vaccines available whose objective is to reduce the risk of suffering severe forms of the disease and dying from covid-19.

The covid-19 pandemic has had an unprecedented impact on the world and has caused significant changes in the way we live and interact. On the other hand, this pandemic has also demonstrated the importance of international collaboration in the fight against infectious diseases and has revealed what can be achieved in research if the necessary resources are used.

The hiv

The human immunodeficiency virus (HIV) is the virus that causes acquired immunodeficiency syndrome (AIDS), the most advanced stage of the infection. When a person is infected with HIV and does not receive treatment, the virus attacks and destroys cells of the immune system, weakening our body’s defenses against other infections and certain types of cancer.

Despite being officially identified in 1983, HIV remains one of the world’s biggest public health problems, as there is still no vaccine or cure for the infection. It is estimated that the virus has so far infected 81 million people and claimed approximately 40 million lives.

While it is true that there have been some cases of people being cured of the infection, these are isolated cases and not considered to be a widespread cure. Specifically, so far there are three people who have been cured of HIV infection .

There are antiretroviral treatments that are very effective in controlling HIV infection. These drugs are capable of inhibiting the replication of the virus and reducing the viral load in the body, which in turn prevents the progression of the disease towards AIDS and its transmission.

The flu virus

The flu is a contagious disease that affects the respiratory system and is caused by influenza viruses . These viruses are highly contagious and can spread rapidly from person to person, especially in closed environments.

Throughout history there have been several flu pandemics. The most devastating was that of 1918 , when a strain infected a third of the world’s population and caused the death of around 50 million people.

Influenza continues to be a major public health problem around the world. The World Health Organization estimates that each year there are between three and five million severe cases of influenza, and that the disease causes between 290,000 and 650,000 deaths worldwide.

There are steps that can help prevent the spread of the flu. These include annual vaccination and adopting proper hygiene practices, such as frequent hand washing and covering your coughs and sneezes.

the ebola virus

The Ebola virus is a zoonotic virus that causes a serious illness known as Ebola hemorrhagic fever, with a fatality rate of up to 90%. This virus is transmitted through contact with blood, organs, or bodily fluids from an infected animal or person.

The largest epidemic outbreak originated in December 2013 in Guinea. Later it spread to Liberia, Sierra Leone, Nigeria, Senegal, the United States, Spain, Mali and the United Kingdom. This outbreak highlighted the need for a more effective global response to control and prevent the spread of the virus.

So far there is no cure for the disease or a vaccine available that offers complete protection. Therefore, infection prevention and control are essential in the fight against the virus. Research is ongoing to develop effective therapies and vaccines against this infection.

polio virus

The polio virus is the pathogen that causes poliomyelitis, a disease that mainly affects children under five years of age and can cause muscle weakness, irreversible paralysis, and death in the most severe cases. This virus is not one of the most dangerous on this list, but it is one of the most fearful in the population in recent history, especially in the 1940s and 1950s.

Most people infected with the polio virus are asymptomatic. In a small percentage, the virus can enter the central nervous system and destroy motor nerve cells, causing paralysis and muscle atrophy.

Thanks to research, surveillance, rapid response to outbreaks, and the development of different polio vaccines , this virus has been nearly eradicated from much of the world. However, there are still some countries where the disease remains endemic, even detecting a case of polio in the United States in 2022 and traces of the virus in London sewage. Therefore, it is important to continue working to achieve the complete eradication of the disease.

The viruses mentioned in this article are just a few examples of dangerous viruses that have directly affected humans throughout history, but they are not the only ones. Other viruses such as Zika virus, dengue fever, Middle East respiratory syndrome coronavirus (MERS-CoV) and the most recent flu pandemics have taught us the importance of continuing to research and develop treatments and vaccines for these diseases.The Conversation

Jose Manuel Jimenez Guardeño , Ramón y Cajal Researcher, University of Málaga and Ana María Ortega-Prieto , Postdoctoral research associate, University of Málaga