VTPB 221 Great Diseases of The World EPIDEMIOLOGICAL TERMS1 Agent A factor such as a micro organism chemical substance or form of radiation whose presence excessive presence or in deficiency diseases relative absence is essential for the occurrence of a disease Association Statistical relationship between two or more events characteristics or other variables Biologic transmission The indirect vector borne transmission of an infectious agent in which the agent undergoes biologic changes within the vector before being transmitted to a new host Carrier A person or animal without apparent disease who harbours a specific infectious agent and is capable of transmitting the agent to others The carrier state may occur in an individual with an infection that is unapparent throughout its course known as asymptomatic carrier or during the incubation period convalescence and post convalescence of an individual with a clinically recognizable disease The carrier state may be of short or long duration transient carrier or chronic carrier Cause of disease A factor characteristic behaviour event etc That directly influences the occurrence of disease A reduction of the factor in the population should lead to a reduction in the occurrence of disease Census The enumeration of an entire population usually with details being recorded on residence age sex occupation ethnic group marital status birth history and relationship to head of household Chain of infection A process that begins when an agent leaves its reservoir or host through a portal of exit and is conveyed by some mode of transmission then enters through an appropriate portal of entry to infect a susceptible host Cluster An aggregation of cases of a disease or other health related condition particularly cancer and birth defects which are closely grouped in time and place The number of cases may or may not exceed the expected number frequently the expected number is not known Contact Exposure to a source of an infection or a person so exposed Contagious Capable of being transmitted from one person to another by contact or close proximity Direct transmission The immediate transfer of an agent from a reservoir to a susceptible host by direct contact or droplet spread Distribution In epidemiology the frequency and pattern of health related characteristics and events in a population In statistics the observed or theoretical frequency of values of a variable Droplet spread The direct transmission of an infectious agent from a reservoir to a susceptible host by spray with relatively large short ranged aerosols produced by sneezing coughing or talking Endemic disease The constant presence of a disease or infectious agent within a given geographic area or population group may also refer to the usual prevalence of a given disease within such area or group Environmental factor An extrinsic factor geology climate insects sanitation health services etc which affects the agent and the opportunity for exposure 1 Adam Fox Glossary Of Epidemiological Terms The Internet Journal of Pediatrics and Neonatology 2003 Volume 3 Number 1 Enzootic disease The constant presence of a disease or infectious agent within a given geographic area or animal population group may also refer to the usual prevalence of a given disease within such area or group Epidemic The occurrence of more cases of disease than expected in a given area or among a specific group of people over a particular period of time Epidemiology The study of the distribution and determinants of health related states or events in specified populations and the application of this study to the control of health problems Epizoology The study of the distribution and determinants of health related states or events in specified animal populations and the application of this study to the control of health problems Epizootic The occurrence of more cases of disease than expected in a given area or among a specific group of animals over a particular period of time Experimental study A study in which the investigator specifies the exposure category for each individual clinical trial or community community trial then follows the individuals or community to detect the effects of the exposure Exposed group A group whose members have been exposed to a supposed cause of disease or health state of interest or possess a characteristic that is a determinant of the health outcome of interest Health A state of complete physical mental and social well being and not merely the absence of disease or infirmity High risk group A group in the community with an elevated risk of disease Host A person or other living organism that can be infected by an infectious agent under natural conditions Host factor An intrinsic factor age race sex behaviours etc which influences an individual s exposure susceptibility or response to a causative agent Hyperendemic Hyperepizootic disease A disease that is constantly present at a high incidence and or prevalence rate Hypothesis A supposition arrived at from observation or reflection which leads to refutable predictions Any conjecture cast in a form that will allow it to be tested and refuted Immunity active Resistance developed in response to stimulus by an antigen infecting agent or vaccine and usually characterized by the presence of antibody produced by the host Immunity herd The resistance of a group to invasion and spread of an infectious agent based on the resistance to infection of a high proportion of individual members of the group The resistance is a product of the number susceptible and the probability that those who are susceptible will come into contact with an infected person Immunity passive Immunity conferred by an antibody produced in another host and acquired naturally by an infant from its mother or artificially by administration of an antibody containing preparation antiserum or immune globulin Incidence rate A measure of the frequency with which an event such as a new case of illness occurs in a population over a period of time The denominator is the population at risk the numerator is the number of new cases occurring during a given time period 2 Incubation period A period of subclinical or inapparent pathologic changes following exposure ending with the onset of symptoms of infectious disease Indirect transmission The transmission of an agent carried from a reservoir to a susceptible host by suspended air particles or by animate vector or inanimate vehicle intermediaries