Smallpox is an infectious disease unique to humans, caused by either of two virus variants, Variola major and Variola minor. The disease is also known by the Latin names Variola or Variola vera, which is a derivative of the Latin varius, meaning spotted, or varus, meaning “pimple”. The term “smallpox” was first used in Europe in the 15th century to distinguish variola from the “great pox” (syphilis).
Smallpox localizes in small blood vessels of the skin and in the mouth and throat. In the skin, this results in a characteristic maculopapular rash, and later, raised fluid-filled blisters. V. major produces a more serious disease and has an overall mortality rate of 30–35%. V. minor causes a milder form of disease (also known as alastrim, cottonpox, milkpox, whitepox, and Cuban itch) which kills about 1% of its victims.
Long-term complications of V. major infection include characteristic scars, commonly on the face, which occur in 65–85% of survivors. Blindness resulting from corneal ulceration and scarring, and limb deformities due to arthritis and osteomyelitis are less common complications, seen in about 2–5% of cases. -Wikipedia.org
9. The 1918 Flu Pandemic
The 1918 flu pandemic (the Spanish Flu) was an influenza pandemic that spread widely across the world. Historical and epidemiological data are inadequate to identify the geographic origin. Most victims were healthy young adults, in contrast to most influenza outbreaks which predominantly affect juvenile, elderly, or weakened patients. The flu pandemic was implicated in the outbreak of encephalitis lethargica in the 1920s.
The pandemic lasted from March 1918 to June 1920, spreading even to the Arctic and remote Pacific islands. Between 50 and 100 million died, making it one of the deadliest natural disasters in human history. An estimated 50 million people, about 3% of the world’s population (1.6 billion at the time), died of the disease. 500 million, or 1/3 were infected. -Wikipedia.org
8. The Black Death
The Black Death was one of the deadliest pandemics in human history, peaking in Europe between 1348 and 1350. It is widely thought to have been an outbreak of bubonic plague caused by the bacterium Yersinia pestis, but this view has recently been challenged. Usually thought to have started in Central Asia, it had reached the Crimea by 1346. From there, probably carried by fleas residing on the black rats that were regular passengers on merchant ships, it spread throughout the Mediterranean and Europe.
The Black Death is estimated to have killed 30% to 60% of Europe’s population, reducing the world’s population from an estimated 450 million to between 350 and 375 million in 1400. This has been seen as creating a series of religious, social and economic upheavals which had profound effects on the course of European history. It took 150 years for Europe’s population to recover. The plague returned at various times, resulting in a larger number of deaths, until it left Europe in the 19th century. -Wikipedia.org
Malaria is a mosquito-borne infectious disease caused by a eukaryotic protist of the genus Plasmodium. It is widespread in tropical and subtropical regions, including parts of the Americas (22 countries), Asia, and Africa. Each year, there are approximately 350–500 million cases of malaria, killing between one and three million people, the majority of whom are young children in sub-Saharan Africa. Ninety percent of malaria-related deaths occur in sub-Saharan Africa. Malaria is commonly associated with poverty, and can indeed be a cause of poverty and a major hindrance to economic development.
Five species of the plasmodium parasite can infect humans; the most serious forms of the disease are caused by Plasmodium falciparum. Malaria caused by Plasmodium vivax, Plasmodium ovale and Plasmodium malariae causes milder disease in humans that is not generally fatal. A fifth species, Plasmodium knowlesi, is a zoonosis that causes malaria in macaques but can also infect humans.
Malaria is naturally transmitted by the bite of a female Anopheles mosquito. When a mosquito bites an infected person, a small amount of blood is taken, which contains malaria parasites. These develop within the mosquito, and about one week later, when the mosquito takes its next blood meal, the parasites are injected with the mosquito’s saliva into the person being bitten. After a period of between two weeks and several months (occasionally years) spent in the liver, the malaria parasites start to multiply within red blood cells, causing symptoms that include fever, and headache. In severe cases the disease worsens leading to hallucinations, coma, and death. -Wikipedia.org
Tuberculosis or TB (short for tubercles bacillus) is a common and often deadly infectious disease caused by various strains of mycobacteria, usually Mycobacterium tuberculosis in humans. Tuberculosis usually attacks the lungs but can also affect other parts of the body. It is spread through the air, when people who have the disease cough, sneeze, or spit. Most infections in humans result in an asymptomatic, latent infection, and about one in ten latent infections eventually progresses to active disease, which, if left untreated, kills more than 50% of its victims.
A third of the world’s population are thought to be infected with M. tuberculosis, and new infections occur at a rate of about one per second. The proportion of people who become sick with tuberculosis each year is stable or falling worldwide but, because of population growth, the absolute number of new cases is still increasing. In 2007 there were an estimated 13.7 million chronic active cases, 9.3 million new cases, and 1.8 million deaths, mostly in developing countries.
In addition, more people in the developed world are contracting tuberculosis because their immune systems are compromised by immunosuppressive drugs, substance abuse, or AIDS. The distribution of tuberculosis is not uniform across the globe; about 80% of the population in many Asian and African countries test positive in tuberculin tests, while only 5-10% of the US population test positive. -Wikipedia.org
(An X-ray of someone with the Tuberculosis cough)
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Cholera is a severe bacterial infection caused by the bacteria Vibrio cholerae, which primarily affects the small intestine. The main symptoms include profuse watery diarrhea and vomiting. Transmission is primarily by the acquisition of the pathogen through contaminated drinking water or infected food. The severity of the diarrhea and associated vomiting can lead to rapid dehydration and electrolyte loss, which can lead to death.
Cholera is a major cause of death in the world. The study of cholera has been used as an example of early epidemiology. Study of the V. cholerae bacterium has also shed light on many of the mechanisms used by bacteria to infect and survive in their hosts. -Wikipedia.org
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS) is a disease of the human immune system caused by the human immunodeficiency virus (HIV). This condition progressively reduces the effectiveness of the immune system and leaves individuals susceptible to opportunistic infections and tumors.
HIV is transmitted through direct contact of a mucous membrane or the bloodstream with a bodily fluid containing HIV, such as blood, semen, vaginal fluid, preseminal fluid, and breast milk. This transmission can involve anal, vaginal or oral sex, blood transfusion, contaminated hypodermic needles, exchange between mother and baby during pregnancy, childbirth, breastfeeding or other exposure to one of the above bodily fluids.
AIDS is now a pandemic. In 2007, it was estimated that 33.2 million people lived with the disease worldwide, and that AIDS killed an estimated 2.1 million people, including 330,000 children. Over three-quarters of these deaths occurred in sub-Saharan Africa.
Genetic research indicates that HIV originated in west-central Africa during the late nineteenth or early twentieth century. AIDS was first recognized by the U.S. Centers for Disease Control and Prevention in 1981 and its cause, HIV, identified in the early 1980s.
Although treatments for AIDS and HIV can slow the course of the disease, there is currently no known cure or vaccine. Antiretroviral treatment reduces both the mortality and the morbidity of HIV infection, but these drugs are expensive and routine access to antiretroviral medication is not available in all countries. Due to the difficulty in treating HIV infection, preventing infection is a key aim in controlling the AIDS pandemic, with health organizations promoting safe sex and needle-exchange programmes in attempts to slow the spread of the virus. -Wikipedia.org
3. Yellow Fever
Yellow fever is an acute viral hemorrhagic disease. The virus is a 40 to 50 nm enveloped RNA virus with positive sense of the Flaviviridae family. The yellow fever virus is transmitted by the bite of female mosquitos (the yellow fever mosquito, Aedes aegypti, and other species) and is found in tropical and subtropical areas in South America and Africa, but not in Asia. The only known hosts of the virus are primates and several species of mosquito. The origin of the disease is most likely to be Africa, from where it was introduced to South America through the slave trade in the 16th century.
Since the 17th century, several major epidemics of the disease have been recorded in the Americas, Africa and Europe. In the 19th century, yellow fever was deemed one of the most dangerous infectious diseases. Clinically, yellow fever presents in most cases with fever, nausea, and pain and it generally subsides after several days.
In some patients, a toxic phase follows, in which liver damage with jaundice (giving the name of the disease) can occur and lead to death. Because of the increased bleeding tendency (bleeding diathesis), yellow fever belongs to the group of hemorrhagic fevers. The WHO estimates that yellow fever causes 200,000 illnesses and 30,000 deaths every year in unvaccinated populations; around 90% of the infections occur in Africa. -Wikipedia.org
2. Epidemic Typhus
Epidemic typhus (also called “camp fever”, “jail fever”, “hospital fever”, “ship fever”, “famine fever”, “putrid fever”, “petechial fever”, “Epidemic louse-borne typhus,” and “louse-borne typhus”) is a form of typhus so named because the disease often causes epidemics following wars and natural disasters. The causative organism is Rickettsia prowazekii, transmitted by the human body louse (Pediculus humanus corporis).
Feeding on a human who carries the bacillus infects the louse. R. prowazekii grows in the louse’s gut and is excreted in its feces. The disease is then transmitted to an uninfected human who scratches the louse bite (which itches) and rubs the feces into the wound. The incubation period is one to two weeks. R. prowazekii can remain viable and virulent in the dried louse feces for many days. Typhus will eventually kill the louse, though the disease will remain viable for many weeks in the dead louse. -Wikipedia.org
Poliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease spread from person to person, primarily via the fecal-oral route. The term derives from the Greek poliós, meaning “grey”, myelós, referring to the “spinal cord”, and the suffix -itis, which denotes inflammation. Although around 90% of polio infections cause no symptoms at all, affected individuals can exhibit a range of symptoms if the virus enters the blood stream.
In about 1% of cases the virus enters the central nervous system, preferentially infecting and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. Different types of paralysis may occur, depending on the nerves involved. Spinal polio is the most common form, characterized by asymmetric paralysis that most often involves the legs. Bulbar polio leads to weakness of muscles innervated by cranial nerves. Bulbospinal polio is a combination of bulbar and spinal paralysis. -Wikipedia.org
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