The 7 Most Dangerous Viruses in the World

As humankind continues to battle the COIVD virus, we are faced with a future of mystery and wondering exactly what to expect. How will our lives be affected when we get past this threat?
Perhaps one way to get a clue lies in how we have dealt with deadly viruses in the past.

Human beings have fought viruses for thousands of years. For some of these viral diseases, science has developed antiviral medicines and vaccines that have effectively prevented infections from spreading and even allowed infected people to fully recover. And in the case of smallpox, the disease was once totally eradicated and removed from the world entirely.

7 Most Deadly Viruses

Yet we are nowhere near winning the war against viruses altogether. In the last few decades, we have witnessed many deadly viruses that leaped from animals to humans and created massive viral outbreaks, and claimed the lives of thousands of people.

Here are seven (7) of the most deadly viruses the world has ever seen. These are based on both its ability to infect humans and its ability to kill humans once they become infected.

Dengue (Mortality Rate: 20%)


Dengue is a viral infection that is transmitted by mosquitoes. There are a total of four dengue virus (DENV) serotypes — which means a person can get infected four times by DENV.

While most of these DENV infections result in just a mild illness, a few cases can result in acute flu-like illnesses. These cases are complicated are can be quite lethal. They are referred to as severe dengue.

It is this form of severe dengue that is the main cause of serious illness and death in many Latin American and Asian countries. These cases must be treated by medical professionals.
Unfortunately, there is not currently a specific treatment for severe dengue. If a severe case of dengue is detected early enough, its mortality rate can be lowered to around 1%. But left untreated, its mortality increases to around 20%.

Dengue is most prevalent in climates that tropical or sub-tropical, and most cases are found in urban areas. Unfortunately, the infection of this virus has grown incredibly in the last few decades. It is believed that over half of the world’s entire population is threatened by DENV. Presently, there are 100–400 million people who are infected annually by this deadly virus.

Smallpox (Mortality Rate: 30%)


Smallpox began its deadly assault on humans several thousands of years ago. It caused tremendous numbers of deaths from time to time throughout history.

Smallpox was one of the most infectious diseases that caused fever along with a distinctive skin rash. It was circulated primarily by direct face-to-face interactions among people — especially prolonged contact. People became contagious the minute that sores popped up in their throat and mouth. They then spread the deadly virus by sneezing or coughing which caused droplets to be spread to others.

While most people recovered from this virus, around 3 out of 10 infected people died. But lots of survivors from smallpox were left with permanent scars all over their bodies, particularly on their faces. Some of these people were left blind by their smallpox infections.

Rotavirus (Mortality Rate: 33%)


Rotavirus is the primary cause of severe diarrhea in infants and children in the world. It is estimated that around 200–400 million children under the age of five die annually from this deadly virus. The overwhelming majority of these child deaths take place in developing countries.

Rotavirus is spread by fecal-oral transmission. This means it comes from the human waste of an infected person to the mouth of another person. Since it is typically passed among children, there are many potential paths of infection beginning with unclean hands. And unwashed hands can contaminate objects like toys, playground equipment, and clothes. The disease spreads very quickly and easily among groups of children.

Around one Rotavirus case out of 50 will cause severe dehydration from vomiting and crippling diarrhea. Hospitalization is almost always necessary in cases like these, where children can be rehydrated intravenously. Quick and prompt rehydration therapy typically results in a positive outcome, but deaths still occur in developing countries.

Hantavirus (Mortality Rate: 36%)


During the early 1990s, a deadly disease outbreak took place in the region of the Four Corners — which is Colorado, Arizona, Utah, and New Mexico. This mysterious virus was referred to as the Sin Nombre virus, which turned out to be part of the Hantavirus family.

While the other strands of Hantaviruses can be quite fatal, none are as deadly as the strand from the Four Corners outbreak. This lethal disease became known as Hantavirus pulmonary syndrome (HPS).

While rats and mice tend to spread Hantaviruses between themselves, their droppings, saliva, and urine are loaded with viral particles. Even though bites from infected rats or mice are extremely rare, the real danger to humans comes from inhaling airborne dust that has come in contact with rodent droppings.

Even the healthiest people in a community can inhale Hantavirus particles and can get a fatal infection. But the virus is not spread from human to human — rodents are the only means of transmission.

Marburg virus (Mortality Rate: 50%)

marburg virus

The Marburg virus was first discovered by scientists in 1967 when lab workers in Germany experienced small outbreaks after being exposed to infected monkeys that came from Uganda⁵. Like Ebola, the Marburg virus can induce hemorrhagic fever. This means that those who are infected can experience high fever and bleeding all through their bodies, often leading to organ failure, shock, and ultimately death.

While its average mortality rate is around 50%, it rose to more than 80% during the 1998–2000 outbreak that took place in the Democratic Republic of Congo. The mortality rate was equally as high during a 2005 outbreak in Angola.

The Marburg virus is transmitted from person to person either through direct contact, broken skin, sexual relations, secretions, mucous membranes, and other bodily fluids from infected people. It can also be contracted from objects and surfaces that have been contaminated by these infected fluids.

Unfortunately, there is no proven treatment for the Marburg virus. But several potential treatments are currently being evaluated.

Ebola virus (Mortality Rate: 50%)


The very first outbreaks of the Ebola virus took place in the year 1976 in the Democratic Republic of Congo and the Republic of Sudan.

This virus is a severe illness that causes hemorrhagic fever, which attacks the body’s immune system. It causes an extreme loss of fluid and is a severe illness that attacks the immune system. The virus can cause extreme fluid loss as well as death in many cases.

Ebola interferes with the body’s ability to naturally clot blood which can cause severe external and internal bleeding. Shortly after a person has been infected, they usually experience fever, headaches, sore throats, and muscle pain. This is generally followed by a rash, diarrhea, vomiting, and bleeding.

These symptoms occur about 8–10 days coming in contact with the Ebola virus. Fatalities often result from severe dehydration and usually take place less than a week after initial symptoms occur.

The Ebola virus is spread by coming in contact with infected blood or other body fluids of others. The disease can also be contracted by coming in contact with contaminated animals or ingesting contaminated food. Bats and sometimes primates are the main animal carriers of Ebola. The bodies of infected humans and animals remain contagious after death.

However, in comparison to other viruses and diseases, the Ebola virus is relatively hard to contract. This is because it is not airborne like many viruses.

Rabies (Mortality Rate: over 90%)


Rabies is a virus that comes from the scratch or bite of an infected animal. It can be so deadly that when symptoms finally appear, it is usually too late to save the life of the victim.

Rabies is an RNA virus that comes from the rhabdovirus family. If it is not treated early enough, it is usually fatal. This dead virus can affect the human body in two different ways.
It can directly enter the peripheral nervous system (PNS) and move to the brain from there.

It can replicate within the tissue of human muscle tissue, where it’s protected from the body’s immune system. From this point, it will invade the nervous system via the neuromuscular junctions.

After it penetrates the body’s nervous system, the virus creates acute inflammation in the brain. Coma and death come shortly thereafter.

Stray dogs are the world’s biggest spreaders of rabies. These rabid animals are most prevalent in Africa and Asia.