Terminology of epidemiology – This book covers the entire syllabus of ” Community Health Nursing” prescribed by the Universities of Bangladesh- for Basic and diploma nursing students. We tried to accommodate the latest information and topics.
This book is an examination-friendly setup according to the teachers’ lectures and examination questions. At the end of the book previous university questions are given. We hope in touch with the book students’ knowledge will be upgraded and flourish. The unique way of presentation may make your reading of the book a pleasurable experience.
Terminology of epidemiology
Epidemiology: Epidemiology has been defined by John M. Last in 1988 as- “The study of distribution and determinants of health-related states or events in specified populations, and the application of this study to the control of health problems.”
Epidemiology approach: Epidemiological approach is defined as the investigation of disease problems. We also implied that such investigations usually have the basic objectives of describing and quantifying disease problems and examining associated between determinants and disease.
Rate: Occurrence of some particular events (e.g., disease) in a given population during a given period of time.
Ratio: A ratio shows the relative sizes of two or more values.
Proportion: The correct or appropriate relationship between the size, shape, and position of the different parts of something. It is a ratio where numerator is a part of whole things (Denomeretor)
Endemic: Enin; demos People It refers to the constant presence of a disease or infectious agent within a given geographic area or the population groups without importation from outside; may also refer to the “usual” of expected frequency of the disease within such area or population group.
Sporadic: When a disease occurs in an inchoate fashion in different areas of a country without having a common source of causative agent. When a disease occurs irregularly, haphazardly from time to time, and generally infrequently without having a common source of infection is known as sporadic. Example: Polio, tetanus, herpes-zoster and meningococcal meningitis
Pandemic: An epidemic usually effecting a large proportion of the population, occurring over a wide geographic area such a section of nation, the entire nation, a continent or the world.
Epidemic: An epidemic is the rapid spread of infectious disease to a large number of people in a given population within a short period of time, usually two weeks or less. For example, in meningococcal infections, an attack rate in excess of 15 cases per 100,000 people for two consecutive weeks is considered an epidemic.
Hyperendemic: The term “hyperendemic” expresses that the disease is constantly present at a high incidence and/or prevalence rate and affects all the age groups equally
Holoendemic: The term “holoendemic” means a high level of infection beginning early in the life & affecting most of the child population leading to a state of equilibrium such that the adult population shows evidence of the disease much less commonly than do the children, as in the case of malaria
Infection: The entry and development or multiplication of an infectious agent in the body of man or animals. It also implies that body responds in some way to defend itself against invader either in the form of immune response or disease. An infection does not always cause illness.
Infection chain: Communicable diseases are transmitted from the reservoir or source of infection to susceptible host which may he designed as follows:
This is infection chain. Basically, there are three links in the chain of transmission-
i. Source of infection or reservoir
ii. Mode of transmission
iii. Susceptible host
Source: The person, animal, object or substance from which an infectious agent passes or disseminated to the host.
Reservoir: It is defined as any person, animal, arthropod, plant, soil or substance in which an infectious agent lives & multiplies in which it depends primarily for survival & where it reproduces itself in such a manner that it can be transmitted to a susceptible host.
Homologous reservoir: The agent infects the same type of host i.e. Reservoir & victims are same species e.g. Man to man-cholera.
Hetemlogous reservoir: The agent infects different types of hosts. e.g. Dog to man Rabies
Definition of Case: A case is defined as “a person in the population or study group identified as having the particular disease, health disorder or condition under investigation
Latent infection: The host does hot shed the infectious agent and lies dormant within the host without sign & symptoms e.g., Herpes simplex
Primary case: The case that develops into the population unit being studied
Secondary case: All cases that develops from primary case within the incubation period.
Index case: The case which is identified or come to attention at first by investigator is called index case.
Source: The person, animal, object or substance from which an infectious agent passes or disseminated to the host.
Reservoir: It is defined as Any person” animal, arthropod, plant, soil or substance in which an infectious agent lives & multiplies in which it depends primarily for survival & where it reproduces itself in a such a manner that it can be transmitted to a susceptible host.
Carrier: It is defined as infected person or animal that harbours a specific infectious agent in the absence of discernible clinical disease and serves as a potential source of infection for other,
Example: Typhoid Mary” is a classic example of a carrier
Incubatory carrier: Agent are shedding during incubation period of disease but pt. has not been suffered e.g. Measles, diphtheria. Mumps, Hepatitis-B, Polio, pertussis. Influenza.
carrier: Agents are shedding during the convalescent period of disease. Patient has been suffered. e.g. Typhoid fever. Dysentery, cholera, Diphtheria, whooping cough.
Healthy carrier: Disease spread by apparently healthy person due to sub-clinical infection: e.g. Polio, Cholera, Meningococcal, meningitis, typhoid fever, and diphtheria
Incubation period: is the time interval between the entry of disease agent and the onset of clinical manifestation of the disease.
- Short: Few hours to few days
- Long: Months to years
- Intermediate: One week to 3 weeks
Definition of isolation: It is defined as “separation for the period incommunicability of infected persons or animals from others in such places and under such conditions as to prevent or limit the direct or indirect transmission of the infectious agent from those infected to those who are susceptible or who may spread the agent to others.
Ring Isolation: The infected person is surrounded by immunized persons. So infection cannot spread to susceptible hosts. E.g. Small pox, Measles.
Chemical isolation: Rapid treatment of cases in their own homes and thus rendering then non- infectious. Physical + Chemical isolation – TB. Leprosy and STD Isolation has a distinctive value in control some infectious diseases – e.g. Diphtheria, Cholera, etc. Isolation is useless in some disease- e.g. Polio. Hepatitis A, Typhoid fever. Mumps, Leprosy. Tuberculosis. STD. etc.
Quarantine: It has been defined as, the limitation of freedom of movement of such well persons or domestic animals exposed to communicable disease for a period of time not longer than the longest usual incubation -period of the disease, in such manner as to prevent effective contact with those not so exposed.
Disease notification: A notifiable disease is any disease required by law to be notified to the government or other health authority. Diseases to be notified to WHO are outlined in the International Health Regulations but most countries have their own list of nationally notifiable diseases.
156 Making a disease legally ‘notifiable’ by doctors and health professionals allows for intervention to control the spread of highly infectious diseases such as influenza, poliomyelitis or yellow fever. In less infectious conditions it improves information about the burden and distribution of disease
Case fatality rate: In epidemiology, a case fatality rate (CFR) or case fatality risk, case fatality ratio or just fatality rate is the proportion of deaths within a designated population of “cases” (people with a medical condition) over the course of the disease.
Definition of Zoonosis: A disease that can be transmitted from animals to people or, more specifically, a disease that normally exists in animals but that can infect humans. There are multitudes of zoonotic diseases. examples include: anthrax.
[Ref: K Park/26/100-132]
Read more: