Since before the evolution of our species, humans have been fighting viruses. Vaccines and antiviral medications have been able to prevent some viral diseases from spreading and have helped people who are ill recover. We have been able eradicate smallpox, thereby eradicating the threat to the entire world.
We are still far from being able to defeat viruses. Many viruses have spread from animals to people over the past decades, causing large outbreaks that claimed thousands of lives. The virus that caused the 2014-2016 Ebola epidemic in West Africa is estimated to have killed as many as 90% of those it infected, making it the most deadly member of the Ebola clan.
Related: 20 of The Worst Pandemics and Epidemics in History
There are many other viruses that can be equally deadly and even more dangerous. While some viruses are less deadly than others, such as the novel coronavirus, which is currently causing outbreaks all over the world, they still pose a threat to public safety and health because we don't have the resources to fight them.
These are the 12 most deadly killers. They are ranked based on how likely it is that someone will die from one of them, how many people they have killed, as well as whether or not they pose a growing threat.
Marburg virus
Marburg virus causes hemorhagic fever in non-human primates and humans. Image credit: ROGER HARRIS/SCIENCE PHOTO LUBARY via Getty Images
According to the World Health Organization (WHO), scientists first discovered the Marburg virus in 1967 when small outbreaks were reported among German lab workers who had been exposed to infected monkeys from Uganda. Marburg virus symptoms can be similar to Ebola. Both viruses can cause hemorhagic fever. Infected individuals can experience high fevers and bleeding throughout their bodies that can lead to shock, organ failure, or death.
According to WHO, the case fatality rate for the first epidemic (1967) was 24%. However, it was 83% for the 1998-2000 DRC outbreak and 100% for the 2017 Ugandan outbreak.
In August 2021, the first Marburg virus epidemic in West Africa was reported. A male from South-West Guinea was the victim. He suffered from a fever, headache and fatigue as well as severe gingival hemorhage. According to Reuters, the outbreak lasted six weeks. Although there were 170 high risk contacts, only one confirmed case was reported.
Ebola virus
Microscopic image showing an Ebola virus. Image credit: Shutterstock
In 1976, the Republic of the Sudan and the Democratic Republic of Congo experienced the first Ebola epidemics. Ebola can be spread by contact with blood, other bodily fluids, or tissue of infected animals or people. Elke Muhlberger of Boston University, an expert on Ebola virus and associate professor in microbiology, said that the deadlines for different strains are very different.
Essential Human Virology (2016) claims that Ebola Reston is the only strain that can make people sick. The fatality rate for the Bundibugyo and Sudan strains is as high as 50%.
According to WHO, the West African outbreak began in 2014 and is the most severe and complex.
The Ervebo vaccine received approval from the U.S. Food and Drug administration in December 2020. This vaccine is used to protect against Zaire's ebola virus. A global stockpile was created in January 2021.
Rabies
The electron microscope shows the rabies virus particles as well as the Negri bodies (which contain virus proteins) in this image. Image credit: CDC/ Dr. Fred Murphy
Although the introduction of rabies vaccines to pets in the 1920s has made the disease far less common in developed countries, it is still a problem in India and other parts of Africa.
After a bite or scratch, this virus can infect you. The brain and nerves can be damaged. According to the National Health Service, almost all deaths occur once symptoms start to manifest.
Muhlberger stated that rabies can cause brain damage and is a very, very serious disease. She said that there is a vaccine for rabies and antibodies against it. This means that if someone is bitten by a rabid creature, they can treat them.
She said that if you do not get treatment, there is a 100% chance you will die.
HIV
This scan electron microscope image shows how the human immunodeficiency viruses (HIV) infects a cell. (Image credit Cynthia Goldsmith, Centers for Disease Control and Prevention).
HIV is the most deadly virus in the modern world. "It's still the most deadly," Dr. Amesh Adalja said, an infectious disease physician who is also the spokesperson for the Infectious Disease Association of America.
Since the early 1980s, HIV has claimed the lives of 32 million people. Adalja stated that HIV is the most serious infectious disease currently affecting mankind.
People can live with HIV for many years thanks to powerful antiviral medications. However, the disease continues its devastating impact on many low- and medium-income countries where 95% of new HIV infections are occurring.
According to the WHO, nearly one in 25 African adults is HIV-positive. This means that more than two-thirds worldwide are living with HIV. There were 680,000 HIV-related deaths in 2020.
Smallpox
A smallpox vaccine (Image credit: CDC/ J. Nakano).
The World Health Assembly declared smallpox free in 1980. According to BBC, smallpox killed approximately 1 in 3 people it infected. Many people were blinded or left with permanent scarring.
Mortality rates in countries other than Europe were much higher because people had not been exposed to the virus before they arrived. According to historians, 90% of America's native population died of smallpox brought by European explorers. According to the BBC, 300 million people died from smallpox in the 20th century.
Adalja stated that the disease was a major burden on the Earth, causing not only death, but also blindness. This is what prompted the campaign to eradicate it from the Earth.
Hantavirus
This image is a transmission electron microscope view of the hantavirus, also known as Sin Nombre virus (SNV). This virus was responsible for an outbreak in the Four Corners area of the United States in November 1993. Image credit: Cynthia Goldsmith. CDC/ Brian W.J. Mahy, PhD; Luanne H. Elliott, M.S.)
According to the Centers for Disease Control and Prevention, the CDC, Hantavirus pulmonary Syndrome (HPS), was first recognized in the United States in 1993. Shortness of breath was a common symptom in a young Navajo couple. Health authorities discovered hantavirus in a deer mouse that had been living in the home and later isolated it from the patient. According to the CDC, HPS has now infected more than 600 Americans and caused 36% of deaths.
The virus cannot be transmitted from one person or to another. Instead, the disease is contracted by people who are exposed to the droppings infected mice.
According to a paper published in Clinical Microbiology Reviews in 2010, a different strain of hantavirus was responsible for an outbreak during the Korean War. Over 3,000 United Nations troops were infected and approximately 12% died.
Although the virus was not yet known to Western medicine at the time it was discovered in the U.S. however, researchers later realized that Navajo medical traditions described a similar disease and were able to link the disease with mice.
Influenza
This image, digitally colored, shows the H1N1 flu virus under a transmission electron microscope. This virus, then known as the swine influenza, caused a pandemic in 2009 and has been estimated to have killed more than 200,00 people around the world. (Image credit to National Institute of Allergies and Infectious Diseases - NIAID).
According to WHO, flu season can see up to 650,000 deaths worldwide. However, pandemics can occur when there is a new strain of flu. This results in a rapid spread of the disease and often higher mortality rates.
According to CDC, the most severe flu pandemic in history, also known as the Spanish flu, occurred in 1918. It affected up to 40% of the population and killed an estimated 50 million people.
Muhlberger stated that he believes it is possible for an outbreak of the 1918 flu to occur again. "We would be in serious trouble if a new strain of influenza found its way into the human population. It could easily spread between people and cause severe illness.
Dengue
This image shows round, dengue virus particles under transmission electron microscope. The bite of infected mosquitoes transmits dengue virus to humans. (Image credit: Frederick Murphy. Provided by CDC/ Frederick Murphy and Cynthia Goldsmith
Clinical Microbiology Reviews reports that dengue virus was first discovered in the Philippines and Thailand in the 1950s. It has since spread to other tropical and subtropical areas of the world, as well, according Clinical Microbiology Reviews. According to Nature, up to 40% of the world’s population lives in areas where dengue virus is endemic. The disease is expected to spread further as the world heats.
According to WHO, 100-400 million people are affected by dengue fever each year. Although dengue fever has a lower mortality rate than other viruses (around 1%), the virus can still cause Ebola-like diseases like dengue hemorhagic fever. This condition, which is fatal if not treated, has a 20% mortality rate. Muhlberger stated that dengue virus poses a threat to the world and called for more attention.
According to the CDC, a vaccine against dengue was approved by the U.S. Food and Drug Administration in 2019. It is intended for children aged 9-16 years who live in areas where dengue is common and have a history of infection. A vaccine for dengue is available in some countries. However, the recipients must have had a confirmed case of dengue previously. If the vaccine is not given, those who have never been infected could become severely dengue-infected.
Rotavirus
Here are Rotaviruses particles under very high magnification at 455,882X. (Image credit: CDC/ Dr. Erskine L. Palmer)
There are two vaccines available now to protect children against rotavirus. This is the leading cause for severe diarrheal disease among children and babies. Researchers call this the fecal–oral route, which means that tiny particles of feces can be consumed and spread quickly.
Rotavirus infection is rare in children living in developed countries. However, it can be fatal in developing countries where there are few rehydration treatment options.
According to the WHO, there are approximately 25 million outpatient visits each year and 2 million hospitalizations due to rotavirus infection. The vaccine has been shown to reduce the number of rotavirus-related deaths and hospitalizations in countries that have adopted it.
SARS-CoV
(Image credit to CDC/ Dr. Fred Murphy
According to WHO, the virus that causes severe acute respir syndrome (SARS) was first discovered in 2003 in China during an epidemic. According to the Journal of Virology, the virus was first found in bats, but then it jumped into nocturnal mammals called civets, before infecting humans. History.com reports that SARS was first reported in China and spread to 26 other countries. It infected more than 8000 people, and killed more than 770, over several months.
SARS causes body aches and fevers, as well as chills and body pains. It can also progress to pneumonia, which is a serious condition where the lungs inflamed and become filled with pus. According to the CDC, SARS has a 9.6% mortality rate. However, there have not been any new cases since 2000.
SARS-CoV-2
This transmission electron microscope image shows SARS CoV-2, the virus responsible for COVID-19. It was isolated from a US patient. Image credit: NIAID - RML
SARS-CoV-2 is part of the same large virus family as SARS-CoV. It was first discovered in December 2019, in Wuhan, China. Nature suggests that the virus could have originated in bats, and then passed on to humans through intermediate animals.
An extensive quarantine was put in place in Wuhan and other cities. Travel restrictions were also imposed to the affected countries. A worldwide effort was launched to develop vaccines and diagnostics. The virus has claimed more than four million lives since its inception.
According to WHO, people with underlying conditions are at greater risk of contracting the disease SARS-CoV-2 (also known as COVID-19). Common symptoms include a cough, shortness of breath, and loss of taste or scent. More serious symptoms include breathing problems, chest pain, and mobility loss.
The first COVID-19 vaccine was approved by the U.S Food and Drug Administration on August 23, 2021. It was called Pfizer BioNTech. According to Nature, this vaccine was approved in December 2020 after a large clinical trial.
MERS-CoV
Illustration of the MERS virus (a type of coronavirus). (Image credit: Shutterstock)
MERS (the virus that causes Middle East respiratory Syndrome) was first reported in Saudi Arabia in 2012. It also caused an epidemic in South Korea in 2015. MERS is part of the same virus family as SARS-CoV-2 and SARS-CoV-CoV. WHO states that the MERS virus infects camels before it reaches humans. It can cause fever, coughing, and shortness or breath in infected individuals.
MERS is most prevalent in the Middle East. It can lead to severe pneumonia, and has a death rate of approximately 35%. According to the NHS, there is no vaccine to prevent this disease. To reduce your chances of getting infected, you should wash your hands frequently, avoid coming into contact with camels, and refrain from eating products made from raw milk.
Original publication on Live Science
