Temporal and spatial scales in epidemiological concepts

  • Onstad D
  • 13


    Mendeley users who have this article in their library.
  • 10


    Citations of this article.


Traditional concepts in epidemiology are reviewed from ecological, cultural, and logical perspectives. In zoological epidemiology (including the study of human and livestock diseases caused by pathogens), temporal and spatial scales are typically not used in definitions, by hypotheses, and theories concerning epidemic and endemic diseases. The same is true for botanical and theoretical epidemiology, although these two subdisciplines use a different definition of an epidemic than does zoological epidemiology. If hypotheses are to be tested and implemented, more precise concepts that include general temporal and spatial scales are needed. Criteria proposed here for identifying temporal and spatial scales are based on the need for consistency of observation and ecological validity. Consistency of observation depends upon the relative life cycles of the hosts and pathogens and upon the environmental effects that lead to stable or unstable population structures. Pathogens are classified as absent, sporadic, or persistent (endemic). Epidemics can occur in the latter two cases but require a separate evaluation. A definition of an epidemic based on temporal and spatial scales and statistics is proposed for use by all subdisciplines. An epidemic occurs when an indicator variable reaches a statistically unusually high value due to transmission of a pathogen in an ecologically proper space-time unit. Threshold theorems in botanical and theoretical epidemiology are also discussed. These proposals do not directly affect modeling, but changes to hypotheses may influence model analyses. © 1992 Academic Press Limited.

Get free article suggestions today

Mendeley saves you time finding and organizing research

Sign up here
Already have an account ?Sign in

Find this document

Get full text


  • David W. Onstad

Cite this document

Choose a citation style from the tabs below

Save time finding and organizing research with Mendeley

Sign up for free