The deadliest viruses in the world

The deadliest viruses in the world

Even before our species evolved into its modern form, we were fighting viruses as humanity. Vaccines and antiviral drugs for some viral diseases have allowed us to prevent the spread of infections widely and helped heal sick people. In the case of the flower, we managed to eliminate the virus and save the world from new cases.

But we are far from winning our fight against viruses. Over the past decades, countless viruses have spread from animals to humans and have cost thousands of lives, causing serious outbreaks. The virus that caused the 2014-2016 Ebola epidemic in West Africa kills 90% of the infected people, making it the deadliest member of the Ebola family.

But there are other equally deadly viruses, and some are even more deadly. Some viruses, including coronavirus, which are now causing epidemics around the world, have lower fatality rates, but still pose a serious threat to public health because we haven’t yet figured out how to deal with these viruses.

We have listed the 12 deadliest viruses below. The ranking criteria are based on the risk of a person dying if any of these viruses are infected, the number of people killed by viruses, and whether they pose a growing threat.

Marburg virus

Scientists detected the Marburg virus in 1967, when small outbreaks broke out among lab workers who were in contact with infected monkeys brought from Uganda in Germany. The Marburg virus resembles Ebola: it causes both hemorrhagic fever (i.e. high fever is seen in the people it is infected with) and causes bleeding in the body that can lead to organ failure and death.

The mortality rate of the first epidemic was 25%, but in the 1998-2000 epidemic in the Democratic Republic of Congo and the 2005 epidemic in Angola, this rate increased to 80% according to the World Health Organization.

Ebola virus

The first known Ebola outbreaks in humans simultaneously hit the Republic of Sudan and the Democratic Republic of the Congo in 1976. Ebola spreads through contact with infected people or animals through blood or other body fluids. Known derivatives of Ebola vary in mortality.

For example, while Ebola Reston does not even make people sick, the rate of fatality increases to 50% in Bundibugyo and to 71% in Sudan derivative.

The last outbreak erupted in West Africa in early 2014 and was the largest and most complex Ebola outbreak to date.


Although rabies vaccines for pets, which were introduced in the 1920s, made the disease rare in the developed world, rabies remains a serious problem in India and some parts of Africa.

It’s a really bad disease that ruins the brain, but we have rabies vaccine and antibodies that fight rabies. So, we can cure a human bitten by a rabid animal. But if this person cannot access or receive treatment, death is certain.


The most deadly virus in the modern world may be HIV. It is still the virus with the highest mortality rate. It is estimated that 32 million people have died from HIV since it was first introduced in the early 1980s. This figure makes it the most deadly infectious disease in human history.

Although strong antiviral drugs make it possible for people with HIV to live for many years, the disease remains destructive in many low- and middle-income countries where 95% of new HIV infections occur. According to the World Health Organization, one in every 25 adults in the African region is HIV positive. So, two thirds of people living with HIV in the world are in this region.


In 1980, the World Health Assembly announced that there was no smallpox in the world. But before that, people had been struggling with smallpox for thousands of years, and the disease killed about a third of those affected. It caused deep, permanent wounds to the survivors and often blindness.

Mortality rates were much higher in non-European populations that did not come in contact with the virus before colonists brought together. For example, historians estimate that 90% of the native population of the American continent died due to the smallpox virus brought by European colonists. In the 20th century alone, smallpox cost 300 million lives.

This is a virus that is very heavy on the planet due to not only death, but also the blindness it caused, and this caused a great campaign to be erased from the world.


Hantavirus pulmonary syndrome (HPS) caught the attention of the world when a healthy young Navajo man and his fiancee died only days after applying to the hospital with a complaint of shortness of breath in 1993 in the USA. A few months later, health authorities managed to isolate the hantavirus from a mouse living in the home of one of the infected people. To date, 36% of the 600 people infected with this disease have died in the USA.

The virus is not transmitted from person to person. It is transmitted through contact with the feces and urine of infected mice.

Previously, a different type of hantavirus caused another outbreak during the Korean War, in the early 1950s. 3000 soldiers were infected with this virus and 12% died.

Although the virus was new to Western medicine when it was discovered in the U.S., researchers realized in the following years that Navajo medical traditions describe a similar disease and associate it with mice.


In a typical flu season, 500,000 people die from this disease worldwide. But sometimes a new flu virus appears, causing an epidemic where the disease spreads faster and costs more lives.

The deadliest flu pandemic, also called the Spanish flu, started in 1918 and killed 40 million people, affecting 40% of the world’s population.

Scientists find that something like the 1918 flu epidemic will recur. If the new flu virus finds its place in the human population and easily infects people from person to cause severe disease, it will be a big problem.


The Deng virus was first seen in the Philippines and Thailand in the 1950s and has since spread throughout the tropical and subtropical regions of the earth. Today, about half of the world’s population lives in areas where the dengue virus is endemic, and the disease that mosquitoes carry will likely spread further as the world warms.

According to WHO, Deng makes 50 to 100 million people sick every year. Although the mortality rate in Den fever is lower than some other viruses (2.5%), the virus can cause an Ebola-like disease called Deng bleeding fever, and if this disease is not treated, it has a mortality rate of 20%. Experts say we need to think more about this virus, which has become a real threat with global warming.

A Deng vaccine for use in children aged 9-16 years with a confirmed history of virus infection, living in areas where the Deng virus is common, was approved by the U.S. Food and Drug Administration in 2019. In some countries there is an approved vaccine for people aged 9-45, but again, those who are to be vaccinated must have been confirmed in the past. If people who have not been infected before are vaccinated, there is a risk of developing a serious Deng virus.


There are two vaccines available to protect children from rotavirus. This virus causes severe diarrhea in infants and young children and can spread very quickly. It is transmitted through the fecal-oral route, that is, by swallowing small pieces of feces.

Although children rarely die from rotavirus infection in the developed world, the disease is a serious threat in the developing world where treatments for dehydration are not widely available.

WHO estimates that 453,000 children under the age of 5 died worldwide from rotavirus infection in 2008. However, in countries that started to use the vaccine, there are serious decreases in hospitalizations and deaths due to rotavirus.


The virus, which caused severe acute respiratory syndrome (SARS), first appeared in Guandong province of southern China in 2002. The virus probably first appeared in bats, then spread to nocturnal mammals called musk cats and eventually transmitted to humans. After causing an epidemic in China, SARS spread to 26 countries and spread to 8000 people and killed more than 770 people in two years.

The disease causes fever, cold sweating and pain, and often turns into pneumonia. So, the lungs are inflamed and purulent. The mortality rate of SARS is estimated to be 9.6% and no approved treatment or vaccine has been found so far. However, no new SARS cases have been reported since the early 2000s.


SARS-CoV-2 belongs to the same virus family as SARS-CoV, known as coronaviruses, and was first detected in Wuhan, China in December 2019. The virus appeared in bats, possibly like SARS-CoV, and switched to an intermediary animal before infecting humans.

Since its emergence, the virus has been transmitted to tens of thousands of people in China and thousands of other countries. The ongoing epidemic led to the implementation of a comprehensive quarantine in Wuhan and surrounding provinces, restrictions on travel to affected countries, and worldwide efforts to improve diagnosis, treatment and vaccination.

It is estimated that the disease called COVID-19 caused by SARS-CoV-2 has a mortality rate of 2.3%. The elderly and people with health problems who are most at risk of being affected by the disease or its complications. Common symptoms include fever, dry cough, and shortness of breath, and the disease can turn into pneumonia in severe cases.


The virus that caused the Middle East Respiratory Syndrome called MERS caused an epidemic in Saudi Arabia in 2012 and in South Korea in 2015. The MERS virus belongs to the same virus family as SARS-CoV and SARS-CoV-2, and again appeared in bats. The disease is transmitted to camels before passing on to humans, leading to fever, cough and shortness of breath.

MERS often turns into severe pneumonia and has an estimated mortality rate of 30 to 40%. This ratio makes it the deadliest among known coronaviruses that pass from animal to human. As with SARS-CoV and SARS-CoV-2, MERS does not have an approved treatment or vaccine.