Incidence is a measure of disease that allows us to determine a person’s probability of being diagnosed with a disease during a given period of time. Incidence refers to the occurrence of new cases of disease or injury in a population over a specified period of time. It is the number of newly diagnosed cases of a disease in a population. Incidence rate is calculated as: the number of new cases of a disease divided by the number of persons at risk for the disease.
Prevalence is a measure of disease that allows us to determine a person’s likelihood of having a disease. The number of prevalent cases is the total number of cases of disease existing in a population. A prevalence rate is the total number of cases of a disease existing in a population divided by the total population. Prevalence, sometimes referred to as prevalence rate, is the proportion of persons in a population who have a particular disease or attribute at a specified point in time or over a specified period of time. Prevalence differs from incidence in that prevalence includes all cases, both new and preexisting, in the population at the specified time, whereas incidence is limited to new cases only.
Morbidity is a term used to describe ill health. Morbidity rate shows the number of infected people in a particular population. Prevalence is a measure often used to determine the level of morbidity in a population. Measures of morbidity frequency characterize the number of persons in a population who become ill (incidence) or are ill at a given time (prevalence).
Mortality is a term used to describe death. A mortality rate is the number of deaths due to a disease divided by the total population. Mortality rate shows the number of people killed by a certain ailment in a given population.
Health is defined as the condition in which an organism (a host) and all of its parts perform its vital functions normally and properly. According to the according to the World Health organization (WHO), health is defined as a state of physical, mental and social well-being, and not merely the absence of disease or infirmity.
Disease is an impairment of the normal state of an organism or of any of its components that hinders the performance of vital functions. It is a response of a host or an organism to environmental factors (e.g. malnutrition, climates), specific infections agents (viruses, fungi, parasites, bacteria) and inherent defects of the body (e.g. various genetic anomalies).
Salyers A.A and Whitt D.D (2001). Microbiology: diversity, disease, and the environment. Fitzgerald Science Press Inc. Maryland, USA.
Schneider M.J (2011). Introduction to Public Health. Third edition. Jones and Bartlett Publishers, Sudbury, Massachusetts, USA.
Singleton P and Sainsbury D (1995). Dictionary of microbiology and molecular biology, 3d ed. New York: John Wiley and Sons.
Slonczewski J.L, Foster J.W and Gillen K.M (2011). Microbiology: An Evolving Science. Second edition. W.W. Norton and Company, Inc, New York, USA.
Songer T (2005). Study designs in epidemiologic research. Supercourse, (http://www.pitt.edu/~super1/lecture/lec19101/index.htm) (Accesed May 2103).
Stedman’s medical dictionary, 27th edition. Philadelphia: Lippincott, Williams and Wilkins.
Summers W.C (2000). History of microbiology. In Encyclopedia of microbiology, vol. 2, J. Lederberg, editor, 677–97. San Diego: Academic Press.
Taylor LH, Latham SM, Woolhouse ME (2001). Risk factors for disease emergence. Philos Trans R Soc Lond B Biol Sci, 356:983–989.
Willey J.M, Sherwood L.M and Woolverton C.J (2008). Harley and Klein’s Microbiology. 7th ed. McGraw-Hill Higher Education, USA.
Aschengrau A and Seage G.R (2013). Essentials of Epidemiology in Public Health. Third edition. Jones and Bartleh Learning,
Aschengrau, A., & G. R. Seage III. (2009). Essentials of Epidemiology in Public Health. Boston: Jones and Bartlett Publishers.
Biosafety in Microbiological and Biomedical Laboratories. 5th edition. U.S Department of Health and Human Services. Public Health Service. Center for Disease Control and Prevention. National Institute of Health. HHS Publication No. (CDC) 21-1112.2009.
Bonita R., Beaglehole R., Kjellström T (2006). Basic epidemiology. 2nd edition. World Health Organization. Pp. 1-226.