Table 1 Definitions of elimination and related concepts as they have changed over time

"Regional eradication" implies a basically unstable situation, because at any time the infection may be reintroduced by carriers or vectors from the outside.

The word elimination is used according to its derivation from the Latin ex and limen - beyond a threshold. Since a threshold is involved, this is not a final process and the threshold specified may vary from disease to disease. In general, the agent may be permitted to persist as long as it does not - or only vary rarely - cause human disease. Alternatively the threshold may be the boundaries of a defined geographic area.

Elimination is the disappearance of transmission of an infection from a small or large area, with a country or a continent ultimately becoming free from infection. Though reversible by importation of infection from other areas, the achievement of elimination, even if temporary, is important because it demonstrates the feasibility of ultimate eradication throughout the world.

Regional elimination is the complete cessation of indigenous transmission in a defined geographic area, with the implication that, depending on frequency of importations and ease with which they can be contained, certain control measures can be modified or dropped.

Refers to cessation of transmission of a disease in a single country, continent, or other limited geographic area, rather than global eradication (e.g., polio in the Americas). It is also theoretically possible to "eliminate" a disease in humans while the microbe remains at large (e.g., neonatal tetanus). Although a disease itself may remain, a particularly undesirable clinical manifestation of it may be prevented entirely (e.g., blindness from trachoma) or new transmission interrupted (e.g., infectious yaws). Control of a disease or its manifestations to a level that it is no longer considered "a public health problem," as an arbitrarily defined qualitative (e.g., onchocerciasis in West Africa) or quantitative (e.g., leprosy incidence below one case per 10,000 population) level of disease control.

Reduction to zero of the incidence of infection caused by a specific agent in a defined geographic area as a result of deliberate efforts; continued measures to prevent reestablishment of transmission are required.

Nationwide per year fewer than three 'epidemiologically linked' cases of malaria infection without an identifiable risk factor other than local mosquito transmission, for three consecutive years.

Interrupting local mosquito-borne malaria transmission in a defined geographical area, i.e. zero incidence of locally contracted cases, although imported cases will continue to occur. Continued intervention measures are required.