Name
Chamberlain University
NR-442 Community Health Nursing
Prof. Name
Date
This week focuses on epidemiology (Chapter 5) and communicable diseases (Chapter 26). Both chapters provide essential frameworks for understanding how diseases are distributed, transmitted, and prevented in populations.
Epidemiology is the study of how determinants of health and disease are distributed within human populations. It incorporates models, concepts, and tools to analyze patterns and establish cause-and-effect relationships.
This model explores who is affected, where the cases occur, and when they appear.
Epidemiological studies consider three core components:
Agent (Etiologic factors):
Nutritive elements: deficiencies or excesses
Chemical agents: poisons, allergens
Physical agents: ionizing radiation, mechanical injuries
Infectious agents: metazoa, protozoa, bacteria, fungi, rickettsia, viruses
Host (Susceptibility/Response to Agent):
Genetic makeup
Age
Sex
Ethnic group
Physiological state
Prior immunological experience (active/passive)
Intercurrent or preexisting disease
Human behavior
Environment (Extrinsic factors):
Physical environment
Biological environment: human populations, flora, fauna
Socioeconomic environment: occupation, urbanization, economic development, social disruption
A fundamental model including agent, host, and environment.
This approach emphasizes macro-level socioenvironmental factors along with microbiological processes in understanding health and illness.
Epidemiologists measure disease occurrence using incidence, prevalence, and rates.
| Calculation | Example | Result |
|---|---|---|
| Incidence rate | 15 students newly positive for TB out of 500 screened | 15/500 = 0.03 (3%) or 30/1000 |
| Prevalence | All existing cases of a condition at a given time | — |
| Crude rates | Summarize occurrences such as births or deaths | — |
| Proportionate Mortality Ratio (PMR) | % of deaths from a specific cause vs. all causes | — |
Six criteria establish causality:
Strength of association
Dose-response relationship
Temporally correct relationship
Biological plausibility
Consistency with other studies
Specificity
Communicable diseases are illnesses caused by infectious agents and spread through transmission.
Latent period: agent replicates before shedding
Communicable period: begins with shedding of the agent
Incubation period: time between invasion and first symptoms (may overlap with communicable period)
The six links in transmission are:
Infectious agent
Reservoirs
Portals of exit
Modes of transmission
Portals of entry
Host susceptibility
Natural immunity:
Active: exposure to disease
Passive: maternal antibodies
Acquired immunity:
Active: vaccination
Passive: monoclonal antibodies, blood products
Primary vaccine failure: no response to vaccine
Secondary vaccine failure: loss of protection after initial success
Diseases are classified as:
Confirmed cases
Probable cases
Laboratory-confirmed cases
Clinically compatible cases
Epidemiologically linked cases
Genetic typing
Clinical case definition
Immunization: broader process of inducing or amplifying immunity (active or passive)
Vaccination: specific act of administering a vaccine or toxoid for active immunity
Immunocompromised individuals
Pregnancy
Mild illness
Stanhope, M., & Lancaster, J. (2020). Foundations of nursing in the community: Community-oriented practice (5th ed.). Elsevier.
Centers for Disease Control and Prevention (CDC). (2021). Principles of epidemiology in public health practice (3rd ed.). U.S. Department of Health and Human Services.
World Health Organization (WHO). (2021). Immunization and vaccines. Retrieved from https://www.who.int
