WordNet

of a disease that is constantly present in an animal community but only occurs in a small number of cases
native to or confined to a certain region; "the islands have a number of interesting endemic species"
a disease that is constantly present to a greater or lesser degree in people of a certain class or in people living in a particular location (同)endemic_disease
a plant that is native to a certain limited area; "it is an endemic found only this island"
of or relating to a disease (or anything resembling a disease) constantly present to greater or lesser extent in a particular locality; "diseases endemic to the tropics"; "endemic malaria"; "food shortages and starvation are endemic in certain parts of the world" (同)endemical
an impairment of health or a condition of abnormal functioning
caused by or altered by or manifesting disease or pathology; "diseased tonsils"; "a morbid growth"; "pathologic tissue"; "pathological bodily processes" (同)morbid, pathologic, pathological

PrepTutorEJDIC

(特に病気が)ある地方(住民)に特有の,風土性の;(ある地方・住民に)特有の《+『to』+『名』》 / 風土病,地方病
(体の)『病気』,疾患 / (精神・道徳などの)病気,病弊
女性の話術芸人 =diseur
病気にかかった / 病的な,不健全な(morbid)

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2013/12/11 00:52:31」(JST)

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This article is about the epidemiological meaning of "endemic". For the ecological meaning, see endemism.

In epidemiology, an infection is said to be endemic (from Greek en- in or within + δῆμος demos people) in a population when that infection is maintained in the population without the need for external inputs.^[1] For example, chickenpox is endemic (steady state) in the UK, but malaria is not. Every year, there are a few cases of malaria acquired in the UK, but these do not lead to sustained transmission in the population due to the lack of a suitable vector (mosquitoes of the genus Anopheles).

For an infection that relies on person-to-person transmission to be endemic, each person who becomes infected with the disease must pass it on to one other person on average. Assuming a completely susceptible population, that means that the basic reproduction number (R₀) of the infection must equal 1. In a population with some immune individuals, the basic reproduction number multiplied by the proportion of susceptible individuals in the population (S) must be 1. This takes account of the probability of each individual to whom the disease may be transmitted actually being susceptible to it, effectively discounting the immune sector of the population.

For the disease to be in an endemic steady state:

$\ {R_0} \times {S} = {1}$

In this way, the infection neither dies out nor does the number of infected people increase exponentially but the infection is said to be in an endemic steady state. An infection that starts as an epidemic will eventually either die out (with the possibility of it resurging in a theoretically predictable cyclical manner) or reach the endemic steady state, depending on a number of factors, including the virulence of the disease and its mode of transmission.

If a disease is in endemic steady state in a population, the relation above allows us to estimate the R₀ (an important parameter) of a particular infection. This in turn can be fed into the mathematical model of an epidemic.

While it might be common to say that AIDS is "endemic" in Africa—meaning found in an area—this is a use of the word in its etymological not epidemiological form. AIDS cases in Africa are still increasing, so the disease is not in an endemic steady state. It is correct to call the spread of AIDS in Africa an epidemic.^{[citation needed]}

References[edit]

^ Last, A Dictionary of Epidemiology, 3d ed

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1. 成人におけるライム病の臨床症状 clinical manifestations of lyme disease in adults
2. リウマチ性心疾患の自然史、スクリーニング、およびマネージメント natural history screening and management of rheumatic heart disease
3. シャーガス病の疫学および管理 epidemiology and control of chagas disease
4. 神経系のライム病 nervous system lyme disease
5. 供血者の病歴 blood donor medical history

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