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The Plague of Athens (c. 1652 –1654) by Michiel Sweerts, illustrating the devastating epidemic that struck Athens in 430 BC, as described by the historian Thucydides. The United States Centers for Disease Control and Prevention defines epidemic broadly: "Epidemic refers to an increase, often sudden, in the number of cases of a disease above what is normally expected in that population in ...
The concept of waves in epidemics has implications especially for communicable diseases. A working definition for the term "epidemic wave" is based on two key features: 1) it comprises periods of upward or downward trends, and 2) these increases or decreases must be substantial and sustained over a period of time, in order to distinguish them ...
For a given epidemic or pandemic, the average of its estimated death toll range is used for ranking. If the death toll averages of two or more epidemics or pandemics are equal, then the smaller the range, the higher the rank. For the historical records of major changes in the world population, see world population. [3]
The number of cases varies according to the disease-causing agent, and the size and type of previous and existing exposure to the agent. Outbreaks include many epidemics, which term is normally only for infectious diseases, as well as diseases with an environmental origin, such as a water or foodborne disease. They may affect a region in a ...
Historian Gregory T. Cushman claims that virgin soil epidemics were not the major cause of deaths due to disease among Pacific Island populations. Rather, diseases like tuberculosis and dysentery were able to take hold in Pacific Island populations that had weakened immune systems because of overworking and exploitation by European colonizers. [23]
Smallpox is the first disease, and so far the only infectious disease of humans, to be eradicated by deliberate intervention. [6] It became the first disease for which there was an effective vaccine in 1798 when Edward Jenner showed the protective effect of inoculation (vaccination) of humans with material from cowpox lesions. [10]
Different bat species. While bats are essential members of many ecosystems, [24] they are also frequently implicated as frequent sources of emerging virus infections. [25] Their immune systems have evolved in such a way as to suppress any inflammatory response to viral infections, thereby allowing them to become tolerant hosts for evolving viruses, and consequently provide major reservoirs of ...
An endemic disease always has a steady, predictable number of people getting sick, but that number can be high (hyperendemic) or low (hypoendemic), and the disease can be severe or mild. [3] [4] Also, a disease that is usually endemic can become epidemic. [3] For example, chickenpox is endemic in the United Kingdom, but malaria is not.