Top 10 most dangerous viruses in the world

Thinking about technological advancement, it is clear that the pace at which innovations are being developed is rapidly increasing. 

There was a time when doctors didn’t have a cure for the deadliest viruses, but now, with advancements in technology, treatments and vaccines are being developed much faster. 

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This progress has the potential to improve global health outcomes and save countless lives greatly. However, before COVID-19 came onto the scene, there were the most fatal viruses in the queue, such as Ebola, Zika, and SARS, that posed significant threats to public health. 

Want to know which are the top 10 deadliest viruses in history? Let’s take a closer look at the history of these viruses and their impact on human populations worldwide. 

List of the Top 10 Most Dangerous Viruses in the World

The following table is the list of the top 10 deadliest viruses in the world that posed or can pose significant threats to human health. These viruses have caused widespread outbreaks and have the potential to cause high mortality rates if not properly controlled and treated. 

Virus Name	Description	Estimated Deaths	First Discovered	Additional Information
Rabies	Affects the nervous system, almost 100% fatal once symptoms appear.	~59,000 annually	Ancient times	Vaccination is effective if administered before symptoms appear.
HIV	Attacks the immune system and can lead to AIDS.	~32 million since 1980	Early 1980s	Effective treatments exist, but no vaccine is available.
Smallpox	Causes severe skin lesions and high mortality.	~300 million (20th century)	Ancient Egypt	First disease eradicated by vaccination; last natural case in 1977.
Marburg Virus	Causes hemorrhagic fever with high fatality rates.	~500 (various outbreaks)	1967 (Germany)	Fatality rates can reach 90%.
Ebola Virus	Causes severe hemorrhagic fever, high mortality.	~15,000 (2014-2016 outbreak)	1976 (Sudan)	Fatality rates range from 25% to 90% depending on the strain.
Hantavirus	Causes lung disease and renal failure.	~1,000 annually	See more : Only Eagle Eyes Can Locate The Phone In This Image Within 17 Secs. Can You? Explanation To This Optical Illusion 1950 (Korean War)	Transmitted by rodent droppings; can cause Hantavirus Pulmonary Syndrome.
Bird Flu (H5N1)	Causes severe respiratory illness, high mortality.	~600 (since 1997)	1997 (Hong Kong)	Primarily transmitted from birds to humans; mortality rate around 70%.
Lassa Virus	Causes Lassa fever, endemic in West Africa.	~5,000 annually	1969 (Nigeria)	Transmitted by rodents; can lead to severe complications.
Junin Virus	Associated with Argentine hemorrhagic fever.	See more : Observation Skills Test: You have the eyes of a hawk find the Cat in 30 seconds. ~1,000 (historically)	1958 (Argentina)	Symptoms include bleeding and tissue inflammation.
Crimean-Congo Fever	Causes severe hemorrhagic fever, transmitted by ticks.	~20,000 (historically)	1944 (Crimea)	Fatality rates can reach 40%.
Dengue Fever	Causes flu-like symptoms and severe cases can be fatal.	~25,000 annually	1779 (Southeast Asia)	Transmitted by mosquitoes; severe cases can lead to hemorrhagic fever.
Zika Virus	Causes birth defects if contracted during pregnancy.	See more : Observation Skills Test: You have the eyes of a hawk find the Cat in 30 seconds. ~1,000 (historically)	1947 (Uganda)	Transmitted by mosquitoes; can lead to microcephaly in newborns.
Kyasanur Forest Virus	Causes fever and bleeding, transmitted by ticks.	See more : Observation Skills Test: You have the eyes of a hawk find the Cat in 30 seconds. ~1,000 (historically)	1957 (India)	Endemic in India; symptoms include high fever and muscle pain.
Machupo Virus	Causes Bolivian hemorrhagic fever.	See more : Observation Skills Test: You have the eyes of a hawk find the Cat in 30 seconds. ~1,000 (historically)	1963 (Bolivia)	Transmitted by rodents; can lead to severe bleeding and high mortality.
Hepatitis B	Causes liver infection, can lead to cirrhosis or cancer.	~1.5 million annually	1965 (Africa)	Transmitted through bodily fluids; chronic infection can be life-threatening.
Norovirus	Causes gastroenteritis, highly contagious.	~200,000 annually	1972 (Norway)	Common in outbreaks, especially in closed environments.
Rotavirus	Leading cause of severe diarrhea in children.	~200,000 annually	1973 (USA)	Highly contagious; can lead to severe dehydration in infants.
Influenza Virus	Causes seasonal flu outbreaks, can be severe.	~290,000-650,000 annually	1918 (Spain)	Highly contagious; mortality varies by strain and season.
SARS-CoV-2	Causes COVID-19, respiratory illness with varying severity.	~15 million (2020-2022)	2019 (China)	Highly transmissible; significant global impact on health and society.

Source: DW

Rabies

• Rabies is a viral infection caused by the rabies virus, primarily affecting the central nervous system. 
• It is typically transmitted through bites or scratches from infected animals, particularly dogs, bats, and other mammals. 
• Once the virus enters the body, it travels along the nerves to the brain, where it causes severe inflammation. 
• The incubation period can vary, ranging from a few weeks to several months, but symptoms usually appear within 1 to 3 months after exposure. 
• Early symptoms resemble flu-like signs, including fever, headache, and fatigue, followed by more severe neurological symptoms such as confusion, hallucinations, hydrophobia (fear of water), and paralysis. 
• Rabies can affect individuals of any age, but children are often more vulnerable due to their interactions with animals. Unfortunately, rabies is almost always fatal once symptoms appear, with a mortality rate nearing 100%. 
• Treatment options are limited; however, post-exposure prophylaxis (PEP) with a rabies vaccine and immunoglobulin can prevent the disease if administered promptly after exposure. 
• Preventative measures, such as vaccinating pets and avoiding contact with wild animals, are crucial in reducing the risk of rabies transmission.

HIV

• Human Immunodeficiency Virus (HIV) is a virus that attacks the immune system, specifically CD4 cells, which are essential for fighting infections. 
• HIV is primarily transmitted through sexual contact, sharing needles, and from mother to child during childbirth or breastfeeding. 
• The virus can remain dormant for years, leading to a chronic infection that may not show symptoms initially. 
• As the disease progresses, individuals may experience flu-like symptoms, fatigue, weight loss, and recurrent infections, ultimately leading to Acquired Immunodeficiency Syndrome (AIDS) if untreated. 
• HIV can affect anyone, but certain groups, such as men who have sex with men and individuals with multiple sexual partners, are at higher risk. 
• While there is no cure for HIV, it is treatable with antiretroviral therapy (ART), which helps manage the virus and allows individuals to live longer, healthier lives. 
• The mortality rate for untreated HIV is high, with AIDS-related illnesses being a leading cause of death worldwide.
• Preventative measures, including safe sex practices and needle exchange programs, are essential in reducing the transmission of HIV.

Smallpox

• Smallpox is a highly contagious and deadly disease caused by the variola virus. It was characterised by fever and a distinctive skin rash that developed into pus-filled blisters. 
• Smallpox is transmitted through respiratory droplets or direct contact with infected individuals or contaminated objects. 
• The disease has a significant history, with outbreaks causing millions of deaths before the development of a vaccine. 
• Symptoms typically appeared 7 to 17 days after exposure, initially resembling flu-like signs, followed by the characteristic rash. 
• Smallpox affected individuals of all ages, but it was particularly deadly in infants and young children. 
• The mortality rate varied, but it could reach as high as 30%. The introduction of the smallpox vaccine in the late 18th century led to a global eradication campaign, and smallpox was declared eradicated by the World Health Organisation in 1980. 
• This marked a significant achievement in public health, as it was the first disease to be eradicated through vaccination. 
• Today, smallpox remains a concern in bioterrorism discussions, but the general population is no longer at risk due to the successful eradication efforts.

Marburg Virus

• The Marburg virus is a highly lethal pathogen that causes severe hemorrhagic fever, with a mortality rate reaching up to 90%. 
• It was first identified in 1967 during outbreaks among laboratory workers in Germany who had been exposed to infected monkeys imported from Uganda. 
• The virus spreads through direct contact with the bodily fluids of infected individuals, including blood, saliva, and vomit. 
• Symptoms typically appear within 5 to 10 days and include high fever, severe headache, muscle pain, and gastrointestinal bleeding. 
• The disease can affect individuals of all ages, but the elderly and those with weakened immune systems are particularly vulnerable. 
• Currently, there is no specific antiviral treatment for the Marburg virus; supportive care is crucial to manage symptoms and improve survival chances. 
• The high fatality rate and rapid progression of the disease make it one of the deadliest viruses known. 
• Outbreaks are often localised, but the potential for rapid spread remains a significant concern, especially in areas with limited healthcare resources. 
• Public health measures, including isolation of infected individuals and contact tracing, are essential to control outbreaks and prevent further transmission.

Ebola Virus

• Ebola virus disease (EVD) is caused by several strains of the Ebola virus, with the Zaire strain being the deadliest, exhibiting a mortality rate of up to 90%. 
• First identified in 1976 near the Ebola River in the Democratic Republic of Congo, the virus spreads through direct contact with bodily fluids of infected individuals or animals, such as bats and primates. 
• Symptoms typically appear within 2 to 21 days after exposure and include fever, severe headache, muscle pain, vomiting, diarrhoea, and, in some cases, bleeding. 
• Ebola can affect people of all ages, but those with weakened immune systems are particularly vulnerable. 
• The mortality rate for Ebola varies by outbreak and strain, ranging from 25% to 90%. 
• While there is no specific antiviral treatment for Ebola, supportive care and experimental treatments, such as monoclonal antibodies and vaccines, have shown promise in improving survival rates. 
• Outbreaks are often localised, primarily occurring in Africa, and can lead to significant public health concerns.  
• Preventative measures, including vaccination campaigns and community education, are essential in managing outbreaks and preventing further transmission.

Hantavirus

• Hantavirus refers to a group of viruses transmitted primarily by rodents, with the most notable being the Sin Nombre virus, which causes Hantavirus pulmonary syndrome (HPS). 
• First recognised during the Korean War in the early 1950s, hantavirus is spread through contact with rodent urine, droppings, or saliva and can also be transmitted via inhalation of aerosolised particles. 
• Symptoms typically begin with fever, muscle aches, and fatigue, progressing to severe respiratory distress and potentially death. 
• HPS can affect individuals of any age, but those with pre-existing health conditions may be at greater risk. 
• There is no specific antiviral treatment for hantavirus infections; supportive care is essential for managing symptoms. 
• The mortality rate for HPS can be as high as 38%, depending on the severity of the disease and the promptness of medical intervention. 
• Preventative measures, such as rodent control and proper sanitation, are crucial in reducing the risk of hantavirus transmission, particularly in rural areas where human-rodent interactions are more common.

Bird Flu (H5N1)

• Bird flu, particularly the H5N1 strain, is a highly pathogenic avian influenza virus that primarily affects birds but can also infect humans. 
• The virus was first identified in 1997 in Hong Kong, where it caused severe illness in humans who had close contact with infected poultry. 
• H5N1 spreads through direct contact with infected birds or contaminated environments, and human-to-human transmission is rare. 
• Symptoms in humans can range from mild flu-like signs to severe respiratory distress and pneumonia. 
• The mortality rate for H5N1 in humans is alarmingly high, estimated at around 60%. 
• While the virus can infect individuals of any age, those with underlying health conditions are at greater risk for severe outcomes. 
• Vaccines for H5N1 have been developed, but they are primarily used in poultry to prevent outbreaks. 
• Human vaccines are available but are not widely used unless there is a significant threat of a pandemic. 
• Public health measures, including surveillance of bird populations and biosecurity in poultry farming, are essential to prevent the spread of H5N1 to humans.

Lassa Virus

• Lassa virus is an arenavirus that causes Lassa fever, a viral hemorrhagic illness endemic in parts of West Africa. 
• It was first identified in 1969 in Nigeria, where a nurse contracted the virus. 
• The primary mode of transmission is through contact with the urine or faeces of infected multimammate rats, which are common in rural areas. 
• Human-to-human transmission can also occur, particularly in healthcare settings. Symptoms typically appear 1 to 3 weeks after exposure and can include fever, weakness, and bleeding. 
• The mortality rate for Lassa fever varies but is estimated at around 1% overall, with higher rates in severe cases. 
• All age groups can be affected, but pregnant women are at increased risk of severe disease and complications.
• While there is no specific antiviral treatment for Lassa fever, supportive care and the antiviral drug ribavirin may improve outcomes. 
• Preventative measures, including rodent control and public health education, are crucial in reducing the incidence of Lassa fever in endemic regions.

Junin Virus

• The Junin virus is a member of the Arenavirus family and is responsible for Argentine hemorrhagic fever. It was first discovered in 1958 in Argentina, where it is endemic. 
• The virus is primarily transmitted through contact with infected rodents, particularly the Calomys musculinus species. 
• Human-to-human transmission is rare but can occur, especially in healthcare settings. 
• Symptoms typically appear 1 to 2 weeks after exposure and include fever, headache, muscle pain, and gastrointestinal bleeding. 
• The mortality rate for Argentine hemorrhagic fever can reach 30%, with higher rates in severe cases. 
• The virus can affect individuals of all ages, but those with weakened immune systems are at greater risk. 
• There is no specific antiviral treatment for Junin virus infections, but supportive care is crucial for managing symptoms. 
• A vaccine is available for individuals at high risk, such as healthcare workers in endemic areas. 
• Public health measures, including rodent control and awareness campaigns, are essential in preventing outbreaks and reducing transmission.

Crimean-Congo Fever

• Crimean-Congo hemorrhagic fever (CCHF) is a tick-borne viral disease caused by the Crimean-Congo virus. 
• It was first identified in the 1940s in Crimea and has since been reported in various regions, particularly in Africa, the Middle East, and parts of Asia. 
• The virus is primarily transmitted through tick bites or contact with infected animal blood or tissues. 
• Human-to-human transmission can occur through direct contact with the bodily fluids of infected individuals. 
• Symptoms typically appear 1 to 3 days after exposure and include fever, muscle aches, and bleeding. 
• The mortality rate for CCHF ranges from 10% to 40%, depending on the outbreak and the healthcare response. 
• The virus can affect individuals of any age, but those with pre-existing health conditions may be at higher risk. 
• There is no specific antiviral treatment for CCHF; supportive care is essential for managing symptoms. 
• Preventative measures, including tick control and public health education, are vital in reducing the risk of transmission in endemic areas.

Which viruses are the priority diseases at present?

According to the World Health Organisation (WHO), there are a few viruses that should be given attention since these are the ones that pose the greatest threat to global health. The list includes:

WHO Priority Diseases

• COVID-19
• Crimean-Congo hemorrhagic fever
• Ebola virus disease and Marburg virus disease
• Lassa fever
• Middle East respiratory syndrome coronavirus (MERS-CoV) and Severe Acute Respiratory Syndrome (SARS)
• Nipah and henipaviral diseases
• Rift Valley fever
• Zika
• “Disease X” (a placeholder for an unknown pathogen that could cause a serious international epidemic)

CEPI Priority Pathogens

• Chikungunya
• COVID-19
• Ebola
• Lassa Fever
• MERS
• Nipah
• Rift Valley Fever
• Novel viral threats with epidemic or pandemic potential (Disease X)

NIH ReVAMPP Network Focus

• Viruses from the Bunyavirales order (including hantaviruses, Oropouche virus, Rift Valley Fever, Crimean Congo Hemorrhagic Fever, Lassa Fever)
• Flaviviridae family (dengue, yellow fever)
• Paramyxoviridae family (measles, mumps, Nipah)
• Picornaviridae family (polio, foot-and-mouth disease, myocarditis)
• Togaviridae family (Chikungunya, Venezuelan equine encephalitis)

The WHO, CEPI, and NIH have identified these viruses as high-priority due to their epidemic potential, lack of effective countermeasures, and ability to cause severe disease and public health impact.

Ongoing research aims to develop vaccines and treatments to prepare for potential outbreaks and pandemics caused by these pathogens.

Why is “Disease X” considered a priority?

“Disease X” is considered a priority by the World Health Organisation (WHO) because it represents the potential for a serious international epidemic caused by an unknown pathogen.

This concept was introduced in February 2018 as part of the WHO’s R&D Blueprint for Action to Prevent Epidemics. The inclusion of Disease X acknowledges that future outbreaks may arise from pathogens that have not yet been identified or understood, highlighting the need for proactive measures and flexible planning in public health.

The rationale behind prioritising Disease X stems from historical patterns of emerging infectious diseases, many of which have zoonotic origins—meaning they spill over from animals to humans.

The COVID-19 pandemic, caused by the SARS-CoV-2 virus, exemplifies how an unknown pathogen can lead to widespread health crises.

Experts emphasise that the next significant outbreak could be caused by a novel virus, making it essential to invest in research and development of vaccines, diagnostics, and treatments that can be rapidly adapted to respond to such threats.

By focusing on Disease X, the WHO aims to encourage research into entire classes of viruses rather than just individual strains.

This approach enhances global preparedness and response capabilities, ensuring that health systems can swiftly address unforeseen pathogens and mitigate their impact on public health and society.

Source: https://dinhtienhoang.edu.vn
Category: Optical Illusion