Antibiotic:  any of various substances (e.g. penicillin) produced by microorganisms or made synthetically, that can inhibit or destroy susceptible microorganisms.

Anthropogenic: caused or produced by human activity.

Antigen: any molecule capable of being recognized by the body or T-lymphocyte receptor. Usually a protein molecule that the body's immune system recognizes as foreign.

Asymptomatic: producing or showing no symptoms.

Bacteria: unicellular microorganisms lacking organelles and an organized nucleus, some of which can cause disease.

El Nino/ Southern Oscillation(ENSO): El Nino is the name originally given by local inhabitants to a weak warm current flowing along the coast of Ecuador and Peru. ENSO is an extensive, intensive, atmospheric, and oceanic phenomenon affecting the tropical Pacific Ocean. It is associated with major anomalies in sea surface temperature atmospheric circulation and rainfall patterns. El Nino occurs irregularly, but approximately every four years on average. ENSO events have impacts on fisheries, bird life and mainland weather.

Endemic: term applied to describes sustained, relatively stable pattern of infection within a specified population.

Epidemic: appearance of abnormally high number of cases of infection in a given population; can also refer to non-infectious diseases (e.g. heart disease) or acute events such as chemical toxicity ( See also Pandemic).

Epidemiology: study of the distribution and determinants of health-related states or events in specified populations. Epidemiology is the basic quantitative science of public health.

Epidemiologist: Scientist who studies the distribution and determinants of health-related states in population (See Epidemiology)

Global Warming: the increase in temperature of the earth's atmosphere caused by the enhanced greenhouse effect.

Enhanced Greenhouse effect: the trapping of the sun's warmth in the lower atmosphere of the earth caused by an increase in carbon dioxide, which is more transparent to solar radiation than to the reflected radiation from the earth.

Host: organism upon which another live as a parasite. A host may also be a vector, intermediate host, or reservoir.

Intermediate Host: host of a disease agent other than one in which sexually mature forms of the pathogen occur.

Lymphocyte: involved in antigen-specific immune reactions. Lymphocytes can be subdivided into B-lymphocytes, which produce circulating antibodies, and T-lymphocytes, which are primarily responsible for cell-mediated immunity. T-lymphocytes can be divided into: cytotoxic T-lymphocytes which bind to and kill foreign cells; helper T-lymphocytes which assist antibody production, suppresser T-lymphocytes which inhibit this immune response.

Morphology: the study of the form of things.

Ozone: form of the element oxygen with three atoms instead of the two that characterizes normal oxygen molecules. Ozone (O3) is an important greenhouse gas. The stratosphere contains 90% of all the O3 present in the atmosphere that absorbs harmful ultraviolet radiation. In the troposphere, O3 is a secondary air pollutant that has adverse impacts on health.

Ozone Depletion: reduction of the colorless, unstable gas that absorbs most of the sun's radiation in the stratosphere.

Pandemic: epidemic occurring over very wide areas, crossing international boundaries and usually affecting a large number of people

Paradigm: an example or pattern that exists as the prevailing principle for a school of thought.

Pathogen: a disease-causing agent.

Reservoir: refers to any animal, plant, soil, or inanimate matter in which a pathogen normally lives and multiplies, and on which it depends primarily for survival: e.g. foxes are a reservoir for rabies. Reservoir hosts may be asymptomatic.

Vector: organism that acts as an essential intermediate host or definite host for a human pathogen and that plays an active role in its transmission; for example, Anopheles species are vectors of malaria. This definition excludes mechanical carriers of infective material (such as the snail hosts of schistosomiasis) and reservoir species (such as foxes in the case of rabbits).

Virus: a microscopic organism consisting mainly of nucleic acid in a protein coat multiplying only in living cells and often causing diseases.