Top 10 Deadliest Viruses To Ever Exist

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By Addah Arcilla | July 31, 2014 4:19 PM EST

REUTERS/Saliou Samb
Workers from Doctors Without Borders unload emergency medical supplies to deal with an Ebola outbreak in Conakry, Guinea, March 23, 2014. Health officials fighting an outbreak of Ebola in Guinea on Sunday dispatched specialised medical equipment, imposed restrictions on funerals and sought to contain panic to prevent the fever from spreading. There have been 29 confirmed deaths from the haemorrhagic fever among 59 people killed by a mysterious illness in southeastern Guinea since early February, international medical charity Medecins Sans Frontieres (MSF) said. Picture taken March 23, 2014. REUTERS/Saliou Samb

An out of control Ebola outbreak that is being called the biggest in history is wrecking havoc in West Africa and experts fear that it's far from over. As of July 23, 2014, according to the World Health organization, the Ebola virus disease has claimed 672 lives and has infected 1,201 people. Ebola is highly contagious with a death rate of 90%. Only a mere 10% of its victims survive. It is transferred through direct contact with the blood, secretions and other bodily fluids of infected animals and humans.

Scary as it might sound Ebola is not the only deadly virus known to man. Scientists estimate that there exists about 1031 viruses on earth and here are a few of its deadliest.

1.  Marburg Virus

The Marburg virus causes a rare, but severe hemorrhagic fever that has a fatality rate of 88%. It was first identified in 1967 when outbreaks of hemorrhagic fever cropped up simultaneously in Marburg, where the disease got its name, Frankfurt in Germany and Belgrade, Serbia.

Marburg and Ebola came from the Filoviridae family of viruses. They both have the capacity to cause dramatic outbreaks with the greatest fatality rates. It is transmitted to humans from fruit bats and spreads to humans through direct contact with the blood, secretions and other bodily fluids of infected humans. No anti-viral treatment or vaccine exists against the Marburg virus.

 2. Crimean-Congo hemorrhagic fever (CCHF)

The Crimean-Congo hemorrhagic fever is a common disease transmitted by a tick-Bourne virus. The virus causes major hemorrhagic fever outbreaks with a fatality rate of up to 30%. It is chiefly transmitted to people through tick and livestock. Person-to-person transmission occurs through direct contact with the blood, secretions and other bodily fluids of an infected person. No vaccination exists for both humans and animals against CCHF.

3.  Avian Influenza (Bird Flu)

Avian influenza is an infectious viral disease commonly found in birds, particularly wild waterfowls such as ducks and geese. It can spread to domestic poultry and cause major outbreaks

Most avian viruses are harmless to humans. However, A(H5N1) and A(H7N9) have caused severe infections in people. The fatality rate for A(H5N1) and A(H7N9) is higher than seasonal influenza. The viruses are transmitted through direct contact with live or dead poultry or exposure to the contaminated environment, such as poultry farms and live poultry markets.

4.  SARS

SARS or severe acute respiratory syndrome is a severe respiratory disease caused by coronavirus. It was first reported in Asia before it spread to North America, South America and Europe in a world-wide outbreak in 2003. According to WHO, a total of 8,098 people worldwide were infected during the 2003 outbreak. 774 of these had died.

The SARS virus is transmitted through respiratory droplets produced when coughing or sneezing. Infection occurs when droplets from the cough or sneeze of an infected person lands in the mouth, eyes or nose of another person. Infection can also occur when a person touches an object or a surface contaminated with infectious droplets and then touches the mouth.

5.  Malaria

Malaria is a serious disease caused by Plasmodium parasites that infects Anopheles mosquitoes which feeds on humans. Initial symptoms include high fever, shaking chills, headache and vomiting - symptoms that may be too  mild to be identified as malaria. If not treated within 24 hours, it can progress to severe illnesses that could lead to death.

The WHO estimates that malaria caused 207,000,000 clinical episodes and 627,000 deaths, mostly among African children,  in 2012. About 3.5 billion people from 167 countries live in areas at risk of malaria transmission.

6. Typhoid fever

Typhoid fever is a serious and potentially fatal disease caused by the bacterium Salmonella Typhi. This type of bacteria lives only in humans. People sick with typhoid fever carry the bacteria in their bloodstream and intestinal tract and transmit the bacteria through their stool. 

A person can get typhoid fever by drinking or eating food contaminated with Salmonella Typhi or if contaminated sewage gets into the water used for drinking or washing dishes.

Typhoid fever symptoms include high fever, weakness, headache, stomach pains or loss of appetite. Typhoid fever is determined by testing the presence of Salmonella Typhi in the stool or blood of an infected person. Typhoid fever is treated with antibiotics.

7.  Cholera

Cholera is an acute intestinal infection caused by a bacterium called Vibrio cholera. It has an incubation period of less than a day to five days and causes painless, watery diarrhea that quickly leads to severe dehydration and death if treatment is not promptly given.

Cholera remains a global problem and continues to be a challenge for countries where access to safe drinking water and sanitation is a problem.

8.  Yellow fever

Yellow fever is a hemorrhagic fever transmitted by infected mosquitoes. The yellow is in reference to the yellow colour (jaundice) that affects some patients. The virus is endemic in tropical areas in Africa and South America.

The disease typically occurs in two phases. The first phase typically causes fever, headache, muscle pain and back pain, chills and nausea. Most patients recover from these symptoms while 15% progresses to the toxic second phase. High fever returns, jaundice becomes apparent, patient complains of abdominal pain with vomiting, and bleeding in the mouth, eyes, nose or stomach occurs. Blood appears in the stool or vomit and kidney function deteriorates. 50% of the patients that enter the toxic phase die within 10 to 14 days.

There is no treatment for yellow fever. Patients are only given supportive care for fever, dehydration and respiratory failure. Yellow fever is preventable through vaccination.

9.  Anthrax

Anthrax is a severe infectious disease caused by the bacteria Bacillus anthracis. This type of bacteria produces spores that can live for years in the soil. Anthrax is more common in farm animals, though humans can get infected as well. Anthrax is not contagious. A person can get infected only when the bacteria gets into the skin, lungs or  digestive tract.

There are three types of anthrax: skin anthrax, inhalation anthrax and gastrointestinal anthrax. Skin anthrax symptoms include fever, muscle aches, headache, nausea and vomiting. Inhalation anthrax begins with flu-like symptoms, which progresses  with severe respiratory distress. Shock, coma and then death follows. Most patients do not recover even if given appropriate antibiotics due to the toxins released by the anthrax bacteria. Gastrointestinal anthrax symptoms include fever, nausea, abdominal pain and bloody diarrhea.

Anthrax is treated with antibiotics.

10. HIV

HIV stands for human immunodeficiency virus and it is the causal agent of AIDS. It attacks the immune system, weakening a person's ability to fight infections and disease. HIV is typically caught through contact with blood, semen or vaginal fluid of an HIV-positive person. It can also be passed on by sharing infected needles and from an HIV-positive mother to her baby.

HIV is a worldwide epidemic. According to WHO, 35.0 million people in the world are living with HIV with 2.1 million people getting newly infected by the end of 2013.

HIV/AIDS still has no cure.

(Photo: REUTERS/Saliou Samb / )
Workers from Doctors Without Borders unload emergency medical supplies to deal with an Ebola outbreak in Conakry, Guinea, March 23, 2014. Health officials fighting an outbreak of Ebola in Guinea on Sunday dispatched specialised medical equipment, imposed restrictions on funerals and sought to contain panic to prevent the fever from spreading. There have been 29 confirmed deaths from the haemorrhagic fever among 59 people killed by a mysterious illness in southeastern Guinea since early February, international medical charity Medecins Sans Frontieres (MSF) said. Picture taken March 23, 2014. REUTERS/Saliou Samb
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