10. Spanish Flu
The 1918 flu pandemic (commonly referred to as the Spanish Flu) was an influenza pandemic that spread to nearly every part of the world. It may have been caused by an unusually virulent and deadly influenza A virus strain of subtype H1N1. Historical and epidemiological data are inadequate to identify the geographic origin of the virus. Most of its victims were healthy young adults, in contrast to most influenza outbreaks which predominantly affect juvenile, elderly, or otherwise weakened patients. The flu pandemic has also been implicated in the sudden outbreak of encephalitis lethargica in the 1920s.
Cholera, sometimes known as Asiatic or epidemic cholera, is an infectious gastroenteritis caused by enterotoxin-producing strains of the bacterium Vibrio cholerae. Transmission to humans occurs through eating food or drinking water contaminated with Vibrio cholerae from other cholera patients. The major reservoir for cholera was long assumed to be humans themselves, but considerable evidence exists that aquatic environments can serve as reservoirs of the bacteria.
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, 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, but is also a cause of poverty and a major hindrance to economic development.
Poliomyelitis, often called polio or infantile paralysis, is an acute viral infectious disease spread from person to person, primarily via the fecal-oral route. 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
6. Bubonic Plague
Bubonic plague is the best known manifestation of the bacterial disease plague, caused by the Gram-negative bacterium Yersinia pestis (formerly known as Pasteurella pestis). It belongs to the family Enterobacteriaceae. The term “bubonic plague” was often used synonymously for plague, but it does in fact refer specifically to an infection that enters through the skin and travels through the lymphatics, as is often seen in flea-borne infections. Bubonic plague kills about half of infected patients in 3–7 days without treatment, and may be the Black Death that swept through Europe in the 1340s, killing tens of millions.
Ebola is the virus Ebolavirus (EBOV), a viral genus, and the disease Ebola hemorrhagic fever (EHF), a viral hemorrhagic fever (VHF). The virus is named after the Ebola River Valley in the Democratic Republic of the Congo (formerly Zaire), which is near the site of the first recognized outbreak, a mission hospital run by Flemish nuns, in 1976. There are four recognised species within the ebolavirus genus, which have a number specific strains. The Zaire virus is the type species, which is also the first discovered and the most lethal. Electron micrographs show long filaments, characteristic of the Filoviridae viral family. The virus interferes with the endothelial cells lining the interior surface of blood vessels and coagulation. As the blood vessel walls become damaged and the platelets are unable to coagulate, patients succumb to hypovolemic shock. Ebola is transmitted through bodily fluids, while conjunctiva exposure may also lead to transmission. Ebola first emerged in 1976 in Zaire. However, it remained largely obscure until 1989 when a widely publicized outbreak among monkeys in Reston, Virginia, United States occurred.
4. Human papilloma virus
A human papillomavirus (HPV) is a member of the papillomavirus family of viruses that is capable of infecting humans. Like all papillomaviruses, HPVs establish productive infections only in the stratified epithelium of the skin or mucous membranes. While the majority of the nearly 200 known types of HPV cause no symptoms in most people, some types can cause warts (verrucae), while others can – in a minority of cases – lead to cancers . Most people who become infected with HPV do not know they have it.
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 k 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.
Cancer is a class of diseases in which a group of cells display uncontrolled growth (division beyond the normal limits), invasion (intrusion on and destruction of adjacent tissues), and sometimes metastasis (spread to other locations in the body via lymph or blood). These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, and do not invade or metastasize. Most cancers form a tumor but some, like leukemia, do not. The branch of medicine concerned with the study, diagnosis, treatment, and prevention of cancer is oncology.
Acquired immune deficiency syndrome or acquired immunodeficiency syndrome (AIDS) is a disease of the human immune system caused by the human immunodeficiency virus (HIV). Although treatments for AIDS and HIV can slow the course of the disease, there is currently no vaccine or cure. 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 s** and needle-exchange programmes in attempts to slow the spread of the virus.