Top 10 Most Dreaded Diseases
Nothing perhaps is worse than a mass decimation of the human population due to diseases. Hundreds of thousands of people die each year due to an outbreak of one disease or the other. History is ripe with instances of large-scale deaths brought about by diseases that have reared its ugly head with alarming regularity. It can be due any number of factors, from animals to even a single human host. Summarized below are ten such diseases, in no particular order, that have contributed to millions of deaths since earliest recorded instances.
The Black Death – 75 million Deaths
One of the deadliest epidemic ever to be recorded in the history of human civilization, The Black Death or The Black Plague probably had its origin in Central Asia before moving on to Europe in the late 1340s. It claimed an estimated 75 million people worldwide, with around 20 to 30 million deaths occurring in Europe alone, which amounts to almost one-third to about two-third of the population in Europe.
Polio – 10,000 Deaths since 1916
Poliomyelitis refers to an acute viral disease that mainly affects young children. Also called infantile paralysis or just polio, the disease is highly infectious and gets transmitted from person to person largely through the fecal-oral route. It is derived from the Greek word polio (πολίός), meaning ‘grey’, myelon (µυελός), which stands for ‘spinal cord’, and -itis, which denotes inflammation. Though almost 90% of the cases of polio infections have been found to be asymptomatic, it is common for the affected individual to exhibit a range of symptoms if the virus makes its way to the blood stream. It is only in less than 1% of polio cases, virus have been found to affect the central nervous system, thereby infecting and destroying motor neurons. This in turn leads to muscle weakness and acute flaccid paralysis.
Smallpox – Native Americans suffer a population drop from 12 Mil. to 235,000
Also known by the Latin names Variola or Variola vera, smallpox is a communicable disease that is unique to humans. It is caused by either of two virus types known as Variola major and Variola minor. Of these, Variola major is far more deadlier, with a mortality rate of 30-35%, while Variola minor is responsible for the disease in its mild form called alastrim, which has been fatal for less than 1% of its victims. Survivors may suffer from long-term side effects, which includes the characteristic skin scars, while occasional side effects include blindness caused by corneal ulcerations and infertility in case of male survivors. Smallpox is responsible for the death of an estimated 60 million Europeans, which includes five reigning European monarchs in the 18th century alone. Up to 30% of those infected have died of the disease, including 80% of the children aged below 5, while one third of the survivors have become blind. Fortunately, smallpox happens to be the only human infectious disease that mankind has been successful in eradicating completely from nature.
Cholera – 12,000 Deaths since 1991
Cholera, also known as Asiatic cholera or epidemic cholera, refers to the condition characterized by extreme diarrhea. Caused by the bacterium Vibrio cholerae, the disease gets transmitted to humans by the consumption of contaminated water or food. It is the humans who have long been suspected to be the major reservoir for cholera, though the focus has now shifted to the aquatic environment due to the emergence of new evidence in this field. The disease can be deadly in its most severe forms, and a healthy person can become hypotensive within an hour of the onset of symptoms, with death occurring within just 2-3 hours if no treatment is provided. Generally, the disease progresses from the initial stage of liquid stool to shock in 4-12 hours, with the possibility of death within 18 hours to several days if rehydration treatment is not resorted to.
Ebola – 160,000 Deaths since 2000
The Ebola virus was first discovered in 1976 during outbreaks in Sudan and Zaire that took place simultaneously. It is considered to be a zoonotic virus, currently active in Central Africa where it is having a devastating effect on the population of lowland gorillas. However, in spite of considerable effort on part of the World Health Organization, an animal reservoir capable of sustaining the virus between outbreaks is yet to be identified, though the fruit bat is widely considered to be the most likely candidate. Ebola hemorrhagic fever can be fatal with symptoms ranging from fever, vomiting, diarrhea, generalized pain or malaise, to sometimes even internal and external bleeding. Mortality rates are generally on the higher side, at around 80% – 90%, with hypovolemic shock or organ failure being the most likely cause of death.
Malaria – 2.7 Million Deaths per year – 2800 children per day
A vector-borne disease caused by protozoan parasites, malaria is extremely common in tropical and subtropical regions, which includes parts of the Americas, Asia, and Africa. An infectious disease, it has been found to affect close to 515 million people each year and is responsible for the death of approximately one to three million people, with children forming the majority of them, in Sub-Saharan Africa. The disease is commonly associated with poverty as well as believed to be a cause of poverty as well and a major deterrent to economic development. It is one of the most common infectious diseases and a major public-health problem. It is caused by protozoan parasites of the genus Plasmodium, with the most serious forms of the disease being caused by Plasmodium falciparum and Plasmodium vivax, though other related species are also likely to infect humans. No vaccine for malaria is available as yet though some are under development. Meanwhile preventative drugs should be taken on a regular basis to reduce chances of infection.
Bubonic Plague – 250 Million Europeans Dead (1/3 population)
Bubonic plague is a bacterial disease that affects rodents and fleas, known by the scientific name Xenopsylla cheopsis. The disease gets transmitted to humans when a flea that is carrying the disease bites a person. The flea, on its part, gets infected by biting a rodent, which itself has been infected by the bite of a flea that is carrying the disease. The bacterium multiplies inside the flea and sticks together to form a plug, which blocks the stomach of the flea, causing it to starve. This makes the flea to bite a host voraciously in order to feed, even though it does little to satiate its hunger. This makes the flea to vomit blood containing the bacteria back into the bite wound. This causes the bubonic plague bacterium to infect a new victim, with the flea eventually dying of starvation. A rise in rodent population or any disease outbreaks in rodents is usually the cause of any serious outbreak of plague.
Spanish Flu – Between 1918-19: 50-100 Million dead
The Spanish flu epidemic took place in 1918 and lasted for almost a year, till 1919. It was identified to be a category 5 influenza pandemic caused by Influenza A virus of subtype H1N1, an unusually severe and deadly strain of virus. It was the healthy young adults that were found to be affected the most, which is in contrast to most cases of influenza outbreaks that mostly affects juveniles, elderly, or otherwise weakened patients. The flu, that had spread even to the Arctic and remote Pacific islands has been estimated to have led to the death of 40 to 50 million people while current estimates put the figure at 50 to 100 million people worldwide. This is a figure that perhaps even exceeds the number of victims of the Black Death tragedy. This extraordinary toll was the result of the exceptionally high infection rate, up to about 50% along with the extreme severity of the symptoms, believed to be the result of cytokine storms. Of those infected, almost 2 to 20% succumbed to the disease, in contrast to the normal flu epidemic mortality rate of just 0.1%. Mortality rates of almost 100% were recorded in some remote Inuit villages.
Influenza – 36,000 Deaths per year
Influenza, or just flu, refers to the infectious disease that affects birds and mammals and is caused by RNA viruses of the family Orthomyxoviridae, the influenza viruses. In case of humans, symptoms like fever, sore throat, muscle pains, severe headache, coughing, weakness and general discomfort commonly characterizes influenza infection. In severe cases, influenza can lead to pneumonia, often with fatal consequences, particularly among young children and the elderly. It is easy to mistake influenza with the common cold, though influenza is a much more severe disease caused by a different type of virus. It is likely for patients to exhibit nausea and vomiting, particularly in children, though these symptoms are a strong characteristic of the unrelated gastroenteritis, also referred to as the ‘stomach flu’ or ’24-hour flu.’ It generally gets transmitted from infected mammals through the air by acts of coughs or sneezes, creating aerosols containing the virus, and from infected birds through their droppings. Other modes of transmission of the disease are through saliva, nasal secretions, feces and blood. Contact with these body fluids or with contaminated surfaces also leads to the occurrence of influenza.
AIDS – 25 Million since 1981
AIDS or Aids, that stands for Acquired Immune Deficiency Syndrome or Acquired Immuno Deficiency Syndrome respectively, refers to the collection of symptoms and infections that result due to specific damage caused to the immune system by the Human Immunodeficiency Virus or HIV in case of humans or similar viruses like SIV, FIV, etc, that causes the disease in other species. The late stage of the condition makes individuals prone to opportunistic infections and tumors. There is no known cure for the disease, though treatments for AIDS and HIV do exist that aims to decelerate the virus’ progression. The HIV or similar virus gets transmitted through direct contact of a mucous membrane or the bloodstream with a bodily fluid that contains HIV, for instance blood, semen, vaginal fluid, preseminal fluid, and breast milk. This disease can get transmitted through acts of anal, vaginal or oral sex, during blood transfusion if the blood contain the virus, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth, or breastfeeding, or other exposure to any of the above mentioned bodily fluids. Most researchers peg the origin of the HIV in sub-Saharan Africa sometime during the twentieth century. It has now grown into a pandemic, with some 38.6 million people currently living with the disease worldwide.