Emerging & Re-emerging Infectiious Diseases
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Figure 4 - Long Description

Figure four illustrates a generalized infectious cycle. Two major concepts are demonstrated: the cycle itself and the points along the cycle where infectious disease can be prevented. The cycle begins when a host is infected by either a reservoir or a vector for the pathogen. The individual may infect other hosts in a population or new vectors. The pathogen may also cycle between the vector and a reservoir.

The infectious cycle may be interrupted and disease may be prevented at different points along the cycle. For example, direct person-to-person transmission may be inhibited by proper hygiene and sanitary conditions as well as education. Vector-borne diseases may be prevented by control measures that either kill the vector or prevent its contact with humans. Infection by a pathogen or development of a pathogen within a host may be prevented by vaccination. Finally, drugs may be used to prevent infection or suppress the disease process.

Host - Body of an organism that harbors another organism. The host provides a microenvironment that supports the growth and reproduction of the parasitic organism.

Reservoir - Site, alternate host, or carrier that harbors pathogenic organisms and serves as a source from which other individuals can be infected.

Vector - Living organism that transfers an infective agent from one host to another.

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