The Ebola epidemic in 2014 grew to be the largest Ebola outbreak in history, affecting multiple West African countries and killing more than
How deadly a virus is can be measured by how many it’s killed or what percentage of people die after contracting the virus. With that in mind, here are the 10 most lethal viruses of all time – including many that remain lethal despite the availability of a vaccine.
The 2014 outbreak of Ebola in West Africa led to 28,638 cases and resulted in 11,316 deaths over two years. Prior to that, the biggest outbreak was in Uganda in 2000-2001 when 425 cases including 224 deaths were reported.
The majority of outbreaks have resulted in less than 100 cases. The severity of the virus, spread by contact with blood or other body fluids, differs depending on the strain, with the Zaire strain being the worst. About 50 to 90 percent of people die from Ebola depending on the strain. While one of the most lethal viruses of all time, it’s also one of the rarest. Severe symptoms include a high fever, vomiting and bleeding internally and out of the eyes and mouth.
9. Yellow Fever
Infected mosquitoes spread yellow fever, one of the most dangerous infectious diseases in the 18th and 19th centuries. It remains one of the most lethal viruses of all time, resulting in about 200,000 cases and 30,000 deaths each year. Yellow fever, called that because symptoms in some patients include jaundice or a “yellowing” of the skin, results in a more toxic phase in about 15 percent of patients that affects several body symptoms including the kidneys. Other symptoms may include bleeding from the mouth, nose, eyes and stomach. According to the World Health Organization, up to 50 percent of people who become severely infected and are not treated will die from yellow fever.
Rabies claims about 55,000 lives a year. Rabies is transmitted through animal bites and, if not treated quickly, attacks the brain and almost always causes death. Rabies can cause violent movements, uncontrollable excitement, acute pain, and inability to swallow water, and that’s just the beginning. It then causes mania followed by a coma and death, often from respiratory problems.
7. Hepatitis C
The hepatitis C virus is the leading chronic virus infection leading to death in the United States. While deaths from HIV have been dropping in the United States, deaths from hepatitis C have been steadily increasing. The World Health Organization estimates that about 150 million people are chronically infected with hepatitis C and more than 350,000 people die from hepatitis C-related liver diseases each year. People may be infected for years or decades before symptoms appear. Deaths are usually caused by cirrhosis or liver cancer. People who inject drugs and people who received blood transfusions before 1992, which blood screening was improved, are the most at risk while the disease can also spread through contact with bodily fluids.
Nearly every child in the world becomes infected at least once by rotavirus, the most common cause of vomiting and diarrhea among infants and young children. Following infections are less rare, and adults are rarely infected. While easily managed in countries with adequate health care, the death toll in other countries is what makes it one of the most lethal viruses of all time. The World Health Organization estimates that more than 450,000 deaths occur because of the virus each year.
Influenza, the symptoms of which were first described more than 2,400 years ago by Hippocrates, is one of the oldest of the most lethal viruses of all time. Between 20 million and 100 million deaths were blamed on the Spanish flu outbreak in 1918, the most deadly pandemic on record. Vaccinations are available in developed countries, but different vaccines must be produced each year because new strains emerge. About 3 to 5 million severe illnesses and 250,000 to 500,000 deaths are attributed to influenza worldwide each year.
Measles remains one of the leading causes of death among young children and one of the most contagious diseases worldwide. The CDC estimates that 400 children die each day – 16 per hour – from measles worldwide despite the existence of a safe and effective vaccine for more than 50 years. About 114,900 people, mostly children under 5 years old, died from the measles in 2014. The World Health Organization estimates that 17.1 million deaths were prevented by vaccinations between 2000 and 2014. Complications including severe diarrhea, dehydration, severe respiratory infections like pneumonia and encephalitis, an infection that causes brain swelling, cause most measles-related deaths.
3. Hepatitis B Virus
The World Health Organization estimates that more than 780,000 people die each year from complications of hepatitis B. The virus is spread through contact with blood or other body fluids, making it an occupational hazard to health workers. The disease infects the liver and, like hepatitis C, can result in cirrhosis or liver cancer. While a highly effective vaccine is available, the majority of chronic cases are reported in areas with low access to healthcare.
The Human Immunodeficiency Virus, which causes AIDS and may shut down a person’s immune system, has killed an estimated 34 million people worldwide according to World Health Organization statistics. About 36.9 million people – including an estimated 2.6 million children – were living with the virus in 2014. According to a UNAIDS report, about 17.1 million of that 36.9 million do not know they have the virus and about 22 million do not have access to HIV treatment. People with early diagnosis and effective treatment can live healthy lives. The disease is commonly spread through contact with blood or other body fluids, can also be spread through infected needles, syringes, or from mother to child through pregnancy, birth or breastfeeding.
Smallpox, one of the most lethal viruses of all time, is no more. Smallpox is one of only two infectious diseases considered eradicated by humans thanks to successful vaccinations in the 19th and 20th centuries. Smallpox, which possibly stretches as far back as 10,000 BC, killed about 400,000 Europeans including five reigning leaders during the final years of the 18th century. About 20-60 percent of those infected, increasing to more than 80 percent of infected children, died.
Estimates for smallpox deaths were 300-500 million during the 20th century. About 50 million cases were estimated in the world each year in the early 1950s. A total estimate is not available because of how long the virus was in existence.