Humans have been fighting viruses since the species has existed. For some viral diseases, vaccines and antiviral drugs have prevented widespread infection or helped people recover. And we've even been able to eradicate one disease — smallpox.
Some viruses pose a bigger threat than others. The viral strain that drove the 2014-2016 Ebola outbreak in West Africa kills up to 90% of the people it infects, making it the most lethal member of the Ebola family.
But there are other viruses that are are even deadlier. Some viruses, including the novel coronavirus currently driving outbreaks around the globe, have lower fatality rates, but still pose a serious threat to public health because they infect so many people.
Here are the 12 worst killers, based on the likelihood that a person will die if they are infected with one of them, the sheer numbers of people they have killed and whether they represent a growing threat.
According to the World Health Organization (WHO), the Marburg virus was first identified by scientists in 1967, when small outbreaks occurred among lab workers in Germany who were exposed to infected monkeys imported from Uganda. Marburg virus symptoms are similar to Ebola in that both viruses can cause hemorrhagic fever, meaning that infected people develop high fevers, and bleeding throughout the body that can lead to shock, organ failure and death, according to Mayo Clinic.
The case fatality rate in the first outbreak (1967) was 24%, but it was 83% in the 1998-2000 outbreak in the Democratic Republic of Congo, and 100% in the 2017 outbreak in Uganda, according to the WHO.
The first known Marburg virus outbreak in West Africa was confirmed in August 2021. The case was a male from south-western Guinea, who developed a fever, headache, fatigue, abdominal pain and gingival hemorrhage before ultimately dying of the disease. This outbreak lasted for six weeks and, while there were 170 high-risk contacts, only one case was confirmed, according to Reuters.
In 1976, the first known Ebola outbreaks in humans struck simultaneously in the Republic of the Sudan and the Democratic Republic of Congo. Ebola is spread through contact with blood or other body fluids, or tissue from infected people or animals. The known strains vary dramatically in their deadliness, Dr. Elke Muhlberger, an Ebola virus expert and associate professor of microbiology at Boston University, told Live Science.
One strain, Ebola Reston, doesn't even make people sick, though it is deadly to other primates, according to Essential Human Virology (2016). But for the Bundibugyo strain, the human fatality rate is up to 25%, and it is up to 90% for the Zaire strain.
The largest Ebola outbreak on record emerged in West Africa in early 2014 and took two years to resolve. During that time, it infected 28,652 people and claimed 11,325 lives, according to the Centers for Disease Control and Transmission (CDC).
In December 2020, the Ervebo vaccine was approved by the U.S. Food and Drug Administration. This vaccine helps to defend against the Zaire ebola virus and a global stockpile became available from January 2021.
Dr. Elke Mühlberger is a professor of microbiology and the director of Integrated Science Services at the National Emerging Infectious Diseases Laboratories (NEIDL) at Boston University.
Dr. Mühlberger is a renowned expert in the field of BSL-4 hemorrhagic fever viruses. She has a strong research focus on the highly pathogenic filoviruses, Ebola and Marburg virus. She received her PhD in Virology from the Philipps University Marburg, Marburg, Germany in 1993 and continued to work on filoviruses as an independent PI and group leader in Marburg. In 2008, she joined the Department of Microbiology at Boston University.
Although rabies vaccines for pets, which were introduced in the 1920s, helped to make the disease extremely rare in the developed world, this condition remains a serious problem in India and parts of Africa. About 59,000 people die every year from the virus, according to a 2019 study in the CDC's Morbidity and Mortality Weekly Report.
Infection from this virus develops after a bite or scratch from an infected mammal. Once a person is bitten, they must immediately get rabies vaccines or antibody treatments to prevent the disease from progressing. If they don't, the virus will damage the brain and nerves. Once symptoms begin to show, death almost always follows; the virus has a 99% fatality rate, according to the CDC.
"It destroys the brain, it's a really, really bad disease," Muhlberger said. "We have a vaccine against rabies, and we have antibodies that work against rabies, so if someone gets bitten by a rabid animal we can treat this person," she said.
However, she said, "if you don't get treatment, there's a 100% possibility you will die."
In the modern world, the deadliest virus of all may be HIV.
"It is still the one that is the biggest killer," Dr. Amesh Adalja, an infectious disease physician and spokesman for the Infectious Disease Society of America told Live Science.
An estimated 32 million people have died from HIV since the disease was first recognized in the early 1980s. "The infectious disease that takes the biggest toll on mankind right now is HIV," Adalja said.
Powerful antiviral drugs have made it possible for people to live for years with HIV. And in rare cases, stem cell transplants have cured the disease. But the disease continues to devastate many low- and middle-income countries, where 95% of new HIV infections occur.
Nearly 1 in every 25 adults within the World Health Organization Africa region is HIV-positive, meaning that there are over two-thirds of the people living with HIV worldwide, according to the WHO. In 2021, there were 650,000 HIV-related deaths worldwide.
Dr. Amesh Adalja is an infectious disease physician specialising in emerging infectious diseases, pandemic preparedness, and biosecurity. A Senior Scholar at the Center for Health Security at Johns Hopkins University in Baltimore, Maryland in the United States of America (USA), he is also a spokesman for the Infectious Disease Society of America.
A fellow of the American College of Physicians, and the American College of Emergency Physicians, he obtained a Bachelor of Science degree in industrial management from Carnegie Mellon University in 1995 and graduated from the American University of the Caribbean School of Medicine in 2002.
In 1980, the World Health Assembly declared the world free of smallpox. But before that, humans had battled smallpox for thousands of years, and the more severe version of the disease, Variola major, killed about 30% of those it infected, according to the WHO. It left survivors with deep, permanent scars and, often, blindness.
In populations outside of Europe, where people had little contact with the virus before visitors brought it to their regions, mortality rates were much higher. For example, historians estimate that smallpox, which was introduced by European explorers, killed 90% of the native population of the Americas. In the 20th century alone, smallpox killed 300 million people, according to National Geographic.
"It was something that had a huge burden on the planet, not just death but also blindness, and that's what spurred the campaign to eradicate from the Earth," Adalja said.
Hantavirus pulmonary syndrome (HPS) is a deadly disease for those who contract it, but it has killed relatively few people. It first gained wide attention in the U.S. in 1993, according to the CDC). A healthy, young Navajo man and his fiancée living in the Four Corners area of the United States died within days of developing shortness of breath. A few months later, health authorities isolated hantavirus from a deer mouse living in the home of one of the infected people. More than 833 people in the U.S. have contracted HPS as of the end of 2020, the last year that data was reported for, and 35% have died from the disease, according to the CDC.
The virus is not transmitted from one person to another, rather, people contract the disease from exposure to the droppings of infected mice.
Previously, a different hantavirus, called Korean hemorrhagic fever, caused an outbreak in the early 1950s, during the Korean War, according to a 2010 paper in the journal Clinical Microbiology Reviews. More than 3,000 United Nations troops became infected, and about 12% of them died.
While the virus was new to Western medicine when it was discovered in the U.S., researchers realized later that Navajo medical traditions describe a similar illness, and linked the disease to mice.
Influenza kills a small proportion of the people it infects, at about 1.8 in 100,000 people every year, according to the CDC. But because it infects so many people, it's one of the leading killers worldwide. During a typical flu season, up to 650,000 people worldwide will die from the illness, according to WHO.
And occasionally, a new flu strain emerges, and a pandemic spreads across the globe. Often, these new strains have higher mortality rates than endemic flu.
"I think that it is possible that something like the 1918 flu outbreak could occur again," Muhlberger said. "If a new influenza strain found its way in the human population, and could be transmitted easily between humans, and caused severe illness, we would have a big problem."
Dengue hemorrhagic fever, caused by the dengue virus, is a mosquito-borne disease that first appeared in the 1950s in the Philippines and Thailand. It has since spread throughout the tropical and subtropical regions of the globe, according to a 2009 study in the journal Clinical Microbiology Reviews. Up to 40% of the world's population now lives in areas where dengue is endemic and the disease will spread farther as climate change enables the mosquitoes that carry it to spread to other regions, according to the journal Nature .
According to WHO, dengue infects 100 to 400 million people a year. Although dengue fever has a lower mortality rate than some other viruses, at around 1%, the virus can cause an Ebola-like disease called dengue hemorrhagic fever, which has a mortality rate of 20% if left untreated. "We really need to think more about dengue virus because it is a real threat to us," Muhlberger said.
A vaccine for dengue, called Dengvaxia was approved in 2019 by the U.S. Food and Drug Administration for use in children ages 9 to16 years old living in areas where dengue is common and with a confirmed history of virus infection, according to the CDC. In some countries, an approved vaccine is available for those who are 9 to 45 years old, but again, recipients must have contracted a confirmed case of dengue in the past. Those who have not caught the virus before could be put at risk of developing severe dengue if given the vaccine.
Rotavirus is a diarrheal disease that kills about 200,000 children annually, mostly in Nigeria and India, according to PreventRotavirus, a council dedicated to widespread use of rotavirus vaccines.
The virus can spread rapidly, through what researchers call the fecal-oral route (meaning that small particles of feces end up being consumed).
Thanks to vaccines, children in the developed world rarely die from the infection. But the disease is a killer in the developing world, where rehydration treatments are not widely available.
The WHO estimates that worldwide, there are more than 25 million outpatient visits and two million hospitalizations each year due to rotavirus infections. Countries that have introduced the vaccine have reported sharp declines in rotavirus hospitalizations and deaths.
Two vaccines are now available to protect children from rotavirus, the leading cause of severe diarrheal illness among babies and young children.
The virus that causes severe acute respiratory syndrome, or SARS, was first identified in 2003 during an outbreak in China, according to the WHO. The virus likely emerged in bats initially, then hopped into nocturnal mammals called civets before finally infecting humans, according to the Journal of Virology. After triggering an outbreak in China, SARS spread to 26 countries around the world, infecting 8,096 people and killing more than 774 over the course of several months, according to the CDC.
The disease causes fever, chills and body aches, and often progresses to pneumonia, a severe condition in which the lungs become inflamed and fill with pus. SARS has an estimated mortality rate of 9.6%, however, no new cases of SARS have been reported since the early 2000s, according to the CDC.
SARS-CoV-2 may not kill a huge fraction of the people it infects, but the disease caused by the virus, called COVID-19, has become the leading viral cause of death in since it exploded onto the scene in 2020. As of October 2022, the virus has caused more than 6.57 million deaths worldwide and counting, and has infected at least 626 million people, according to OurWorldInData.
SARS-CoV-2 belongs to the same large family of viruses as SARS-CoV, known as coronaviruses, and was first identified in December 2019 in the Chinese city of Wuhan. The virus may have originated in bats and passed through an intermediate animal before infecting people, according to a 2021 study in the journal Nature.
The initial outbreak prompted an extensive quarantine of Wuhan and nearby cities, restrictions on travel to and from affected countries and a worldwide effort to develop diagnostics, treatments and vaccines.
Estimating an infection fatality rate, or the fraction of people who die after being infected, is difficult, because many mild cases are never diagnosed. But age is clearly a huge factor in the virus' lethality: One study in the journal The Lancet estimated that the virus killed about 0.0023% of children under age 7 that it infected and about 20% of those infected over age 90.
The virus also poses a higher risk to people who have underlying health conditions such as diabetes, high blood pressure or obesity, according to WHO. Common symptoms include fever, cough, loss of taste or smell and shortness of breath and more serious symptoms include breathing difficulties, chest pain and loss of mobility.
Several COVID-19 vaccines, as well as booster doses for those vaccines, are currently approved for use in both children and adults. These vaccines dramatically reduce the odds of severe disease and death, according to the CDC.
The virus that causes Middle East respiratory syndrome, or MERS, sparked an outbreak in Saudi Arabia in 2012 and another in South Korea in 2015. It has a high case fatality rate, killing about 35% of people diagnosed with it. But the virus has killed only 858 people as of 2021, because it does not spread easily between people.
The MERS virus belongs to the same family of viruses as SARS-CoV and SARS-CoV-2. According to WHO, the disease infected camels before passing into humans and can trigger a fever, coughing and shortness of breath in infected people.
MERS is deadly because, like its less lethal cousins SARS and SARS-CoV-2, it often progresses to severe pneumonia. There is no vaccine available to prevent this disease. The best way to reduce the chances of infection is to wash hands regularly, avoid contact with camels and not consume products containing raw animal milk.
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Nicoletta Lanese is the health channel editor at Live Science and was previously a news editor and staff writer at the site. She holds a graduate certificate in science communication from UC Santa Cruz and degrees in neuroscience and dance from the University of Florida. Her work has appeared in The Scientist, Science News, the Mercury News, Mongabay and Stanford Medicine Magazine, among other outlets. Based in NYC, she also remains heavily involved in dance and performs in local choreographers' work.
Not sure where the name SARS-CoV-2 came from. The official WHO name is COVID-19.Reply
Don't said:Not sure where the name SARS-CoV-2 came from. The official WHO name is COVID-19.
The name of the virus itself, free floating without having infected anyone is SARS-CoV-2 (there's also two strains of it, an S and and L strain). When someone is infected with SARS-CoV-2, the disease is called COVID-19. One is the name of the infectious particle, the other is the name of the disease.
Sorry - my mistake. You are correct. COVID-19 is the name of the illness and not the virus itself, and the article is about the viruses. Had I read more closely, my comment would have been "Not sure where the name SARS-CoV-2 came from. The official WHO name is 2019-nCoV ." I am new to all this. My background is engineering - not infectious organisms or diseases. Now having dug a little deeper, I see different groups seem to have different names for the same virus. I note that the WHO says COVID-19 is different from SARS. So that has me wondering why anyone would decide to use SARS in the name if a virus that does not (according to WHO at least) cause SARS.Meh said:The name of the virus itself, free floating without having infected anyone is SARS-CoV-2 (there's also two strains of it, an S and and L strain). When someone is infected with SARS-CoV-2, the disease is called COVID-19. One is the name of the infectious particle, the other is the name of the disease.
See here: https://www.nature.com/articles/s41564-020-0695-z" Thus, the reference to SARS in all these virus names (combined with the use of specific prefixes, suffixes and/or genome sequence IDs in public databases) acknowledges the phylogenetic (rather than clinical disease-based) grouping of the respective virus with the prototypic virus in that species (SARS-CoV). The CSG chose the name SARS-CoV-2 based on the established practice for naming viruses in this species and the relatively distant relationship of this virus to the prototype SARS-CoV in a species tree and the distance space"Don't said:Sorry - my mistake. You are correct. COVID-19 is the name of the illness and not the virus itself, and the article is about the viruses. Had I read more closely, my comment would have been "Not sure where the name SARS-CoV-2 came from. The official WHO name is 2019-nCoV ." I am new to all this. My background is engineering - not infectious organisms or diseases. Now having dug a little deeper, I see different groups seem to have different names for the same virus. I note that the WHO says COVID-19 is different from SARS. So that has me wondering why anyone would decide to use SARS in the name if a virus that does not (according to WHO at least) cause SARS.
Comment on rabies fatality rate. The classic exposure /infection/terminology is difficult to employ when speaking about rabies. Although all warm-blooded animals are thought to be susceptible to rabies, there are strains of the rabies virus ( multiple bat stains ) strains are maintained in particular reservoir host(s), with some cross over especially in the US between raccoons and skunks. Although a strain can cause rabies in other species, the virus usually dies out during serial passage in species to which it is not adapted, and non-carnivores (cows, horses, deer, groundhogs, beavers ) AND CATS, like small rodents, are dead-end hosts. The CDC estimates in the US, 1 million dollars per potential life saved is spent by post-exposure prophylaxis in cases of exposure to animals other than bats, canines, fox, raccoon, skunks. At some point, the inability to PROVE this may be trumped by statistics; when I became a veterinarian in 1975, PEP was still recommended for squirrel and gerbil bites. Hundreds of (unvaccinated) cats are infected with, and die ( or are euthanized) of rabies each year -no way every human exposure to "the kitten in the park " is tracked down. Certainly, many farmers and ranchers are unknowingly exposed. Yet almost all of the 6-9 people diagnosed in the US yearly, knew they were bitten by a dog (when outside the US) or handled a bat. And there have been several incidences since 2000, where people got rabies secondary to solid organ transplants. This had been thought only a risk when transplanting 'nerve' tissue (corneas), I wonder if this reflects better and/or different immunosuppressive drugs in recipients.Reply
Species vary in susceptibility to various strains, humans are 'most' susceptible to canine rabies and, in the US, the silver-haired bat strain. This is a solitary bat with infrequent human interaction, whereas we have much more exposure to big and little brown bats and Mexican free-tailed bats. (Only a small percentage of any of these have rabies, -it kills them too!)
The virus needs to get to a nerve, so if a bite is not deep enough, or a small viral load is deposited, or the 'victim' immune system responds - an infection will never be established. If the virus is able to get to a nerve, it attempts to travel up an axon, to the brain- again, the immune system may eliminate. As rabies is a slow virus, it can self -immunize, explaining the presence of rabies neutralizing antibodies in Amazonian Indians and others who have never been vaccinated? (The reason why a mature dog is considered immunized 28 days after its first rabies vaccination, is if it has been exposed or is 'incubating' rabies virus but the virus is more than 28 days away the vaccine will prevent infection. Although antiglobulin is given, PEP - a killed vaccine, is basically, rapid immunization. I am pulling this from memory but I believe in cases where multiple people were bitten by a rabid dog, in 15% infection was established. Once the the virus is in the brain and /or clinical signs are seen, then it is almost always, fatal. Since definitive diagnosis is made on brain biopsy, the apparent spontaneous cures or response to treatment remain unproven.
Not to diminish the threat or the misery of this disease. I don't understand why the WHO estimate of deaths has been quoted as 35,000 to 55,000 for the last 40 years - while the world population went from approximately 4 billion to 8 billion, mostly in Africa and Asia where few dogs are vaccinated and most cases are seen.
admin said:Humans have been fighting viruses throughout history. Here are the 12 viruses that are the world's worst killers, based on their mortality rates, or the sheer numbers of people they have killed.
... on COVID-19 origin
"The virus likely originated in bats, like SARS-CoV, and passed through an intermediate animal before infecting people. "
dear admin, i don't see solid evidence and facts that this new strain of virus originated from Bats, passing thru animals, then to human. Should we sample and study the Bats or animal carcasses for more evidence? Even the latest chinese scientists from Wuhan flip to suggest that other sources is potential. Indonesia market for example has high appetite for Bats as food.
It seems that humans are passing the virus to dogs and cats now. also, it is well known there is a P4 virus lab located nearby the Wuhan market. my question - is there any regulations that governs the building of such dangerous lab so close to the mass human neighbourhood?
Jim Thompson MD said:See here: https://www.nature.com/articles/s41564-020-0695-z" Thus, the reference to SARS in all these virus names (combined with the use of specific prefixes, suffixes and/or genome sequence IDs in public databases) acknowledges the phylogenetic (rather than clinical disease-based) grouping of the respective virus with the prototypic virus in that species (SARS-CoV). The CSG chose the name SARS-CoV-2 based on the established practice for naming viruses in this species and the relatively distant relationship of this virus to the prototype SARS-CoV in a species tree and the distance space"
And in any case, the World Health Organization (WHO) is not the naming authority for novel viruses — this is the job of the International Committee on Taxonomy of Viruses (ICTV) and in this case specifically the Coronaviridae Study Group (CSG, or ICTV-CSG) which concluded that the virus that causes COVID-19 should be named SARS-CoV-2
The WHO on the other hand is the naming authority for novel diseases, and the name 2019-nCoV for the virus causing COVID-19 was only of a provisional nature, signifying a novel coronavirus discovered in 2019. Official classification of viruses is a scientific process, where the degree of relatedness (of novel viruses to those previously identified) is considered. By actually comparing the genome of the novel coronavirus to the genomes of related viruses, looking at certain replicative proteins, it was clear that SARS-CoV (causing SARS) and SARS-CoV-2 (causing COVID-19) are quite close to each other genetically, even though nothing indicates that the latter is a direct descendent of the former. Both are also much more closely related to other coronaviruses, known to infect Asian and African bats respectively. In contrast, none of them are as closely related to MERS-CoV as they are to each other. On the other hand, these three are more closely related to each other, than any of them are to the other coronaviruses known to infect humans. The three previously discussed (causing major epidemics in recent decades) are zoonotic viruses, meaning they are believed to momentarily “spill over” from animals to humans. The other four coronaviruses infecting humans are common respiratory viruses that circulate continually among us, with symptoms ranging from the common cold (which can be caused by more than 200 virus strains) to more high-morbidity outcomes
it tells you that first was sars 1 that came from bats and hopped into a nocturnal mammal called videts then sars 2 or covid 19 which also came from bats and possibly hopped into other mammals like The Pangolin that has a 99% identical match to the virus. then the sars 3 they al are a family of Coronaviruses.Reply
The name given to the virus is SARS-Cov-2. The name given to the disease caused by the virus is COVID-19.Don't said:Not sure where the name SARS-CoV-2 came from. The official WHO name is COVID-19.
The name given to the virus is SARS-Cov-2. The name given to the disease caused by the virus is COVID-19.Reply