Biological and epidemiological principles
Biological and epidemiological principles.
Chapter 25
Communicable Disease
Save your time - order a paper!
Get your paper written from scratch within the tight deadline. Our service is a reliable solution to all your troubles. Place an order on any task and we will take care of it. You won’t have to worry about the quality and deadlines
Order Paper NowCopyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
Principles of Infection and Infectious Disease Occurrence
Biological and epidemiological principles
Multicausation
Spectrum of Infection
Stages of Infection
Spectrum of disease occurrence
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
2
Multicausation
Disease etiology is complex and multicausal.
An infectious agent alone is not sufficient to cause disease; the agent must be transmitted within a conducive environment to a susceptible host.
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
3
Epidemiological Triad
Host
Agent
Environment
Spectrum of Infection
Not all contact with an infectious agent leads to infection, and not all infection leads to an infectious disease.
Subclinical infection: no overt symptomatic disease (unapparent or asymptomatic)
Infections: entry and multiplication of infectious agent in host
Infectious disease and communicable disease: pathophysiological responses of the host to the infectious agent, manifesting as an illness (considered a case)
Carriers: people who continue to shed infectious agent without any symptoms of disease
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
4
Stages of Infection
Latent period
Infectious agent has invaded a host and found conditions hospitable to replicate
Replication before shedding
Communicable period
Follows latency
Begins with shedding of agent
Incubation period
Time from invasion to time when disease symptoms first appear
May overlap with communicable period
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
5
Stages of Infection (Cont.)
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
6
Figure 25-1 From Grimes DE: Infectious diseases, St Louis, 1991, Mosby.
Spectrum of Disease Occurrence
Incidence—new cases in a population
Endemic—diseases that occur at a consistent, expected level in a geographic area
Outbreak—an unexpected occurrence of an infectious disease in a limited geographic area during a limited period of time
Epidemic—an unexpected increase of an infectious disease in a geographic area over an extended period of time
Pandemic—steady occurrence of a disease over a large geographic area or worldwide
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
7
Chain of Transmission
Infectious agents
Reservoirs
Portals of exit and entry
Modes of transmission
Direct
Indirect
Fomites or vectors
Fecal-oral, airborne
Host susceptibility
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
8
Chain of Transmission (Cont.)
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
9
Figure 25-2
Chain of Transmission: Part 1
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
10
Table 25-1
Links
of the Chain
Definition
Factors
Infectious agent
An organism (virus, rickettsia, bacteria, fungus, protozoan, helminth, or prion) capable of producing infection or infectious disease
Properties of the agent: morphology, chemical composition, growth requirements, and viability.
Interaction with the host: mode of action, infectivity, pathogenicity, virulence, toxigenicity, antigenicity, and ability to adapt to the host
Reservoirs
The environment in which a pathogen lives and multiplies
Humans, animals, arthropods, plants, soil, or any other organic substance
Portal of exit
Means by which an infectious agent is transported from the host
Respiratory secretions, vaginal secretions, semen, saliva, lesion exudates, blood, and feces
Chain of Transmission: Part 2
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
11
Table 25-1
Links of the Chain
Definition
Factors
Mode of transmission
Method whereby the infectious agent is transmitted from one host (or reservoir) to another host
Direct: person to person
Indirect: implies a vehicle of transmission (biological or mechanical vector, common vehicles or fomite)
Airborne droplets
Portal of entry
Means by which an infectious agent enters a new host
Respiratory passages, mucous membranes, skin, percutaneous injection, ingestion, and through the placenta
Host susceptibility
The presence or lack of sufficient resistance to an infectious agent to avoid or prevent contracting an infection or acquiring an infectious disease
Biological and personal characteristics (e.g., gender, age, genetics), general health status, personal behaviors, anatomical and physiological lines of defense, immunity
Breaking the Chain of Transmission
Controlling the agent
Eradicating the nonhuman reservoir
Controlling the human reservoir
Quarantine—during incubation period
Controlling the portals of exit and entry
Isolation of sick persons
Universal precautions
Improving host resistance and immunity
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
12
Types of Immunity
Natural immunity: an innate resistance to a specific antigen or toxin
Acquired immunity: derived from actual exposure to specific infectious agent, toxin, or appropriate vaccine
Active acquired: body produces its own antibodies
Passive acquired: temporary resistance that has been donated to the host
Primary vaccine failure: failure of vaccine to stimulate any immune response
Secondary vaccine failure: waning of immunity following an initial immune response
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
13
Types of Acquired Immunity
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
14
Table 25-2
Type
How Acquired
Length of Resistance
Natural
Active
Natural contact and infection with the antigen
May be temporary or permanent
Passive
Natural contact with antibody transplacentally or through colostrum and breast milk
Temporary
Artificial
Active
Inoculation of antigen
May be temporary or permanent
Passive
Inoculation of antibody or antitoxin
Temporary
Types of Immunity
Herd immunity: a state in which those not immune to an infectious agent will be protected if a certain proportion (generally considered to be 80%) of the population has been vaccinated or is otherwise immune
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
15
Figure 25-3
Public Health Control of Infectious Diseases
Control
The reduction of incidence (new cases) or prevalence (existing cases) of a given disease to a locally acceptable level as a result of deliberate efforts
Elimination
Controlling a disease within a specified geographic area and reducing the prevalence and incidence to near zero
The result of deliberate efforts, but continued intervention measures are required
Eradication
Reducing the worldwide incidence of a disease to zero as a function of deliberate efforts (e.g., smallpox in 1977)
No need for further control measures
Only possible under certain conditions
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
16
Criteria for Disease Eradication
Human host only; no host in nature
Easy diagnosis; obvious clinical manifestations
Limited duration and intensity of infection
Natural lifelong immunity after infection
Highly seasonal transmission
Availability of vaccine, curative treatment, or both
Substantial global morbidity and mortality rates
Cost effectiveness of campaign and eradication
Integration of eradication with additional public health variables
Eradication imperative over control measures
– CDC (1993)
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
17
Notifiable Infectious Diseases in the United States
HCP MUST report to local or regional health departments state health dept. CDC
Reported weekly in the MMWR
Go to CDC website for latest listing of diseases: http://www.cdc.gov
Note: State health departments have the responsibility for monitoring and controlling communicable diseases within their respective states; they determine which diseases will be reported within their jurisdiction. Those lists might be longer than the CDC’s list.
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
18
Vaccines and Infectious Disease Prevention
Immunization is a broad term used to describe a process by which active or passive immunity to an infectious disease is induced or amplified.
Immunizing agents can include vaccines as well as immune globulins or antitoxins.
Vaccination is a narrower term referring to the administration of a vaccine or toxoid to confer active immunity by stimulating the body to produce its own antibodies.
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
19
Recommended Immunization Schedules
Recommendations for international immunization practices determined by WHO
In the United States, AAP and ACIP
Current U.S. recommendations found on CDC website: http://www.cdc.gov/vaccines
Schedules, footnotes, and educational fact sheets provide guidelines for practice
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
20
Vaccines: Words of Caution
Information and recommendations on immunizations and vaccine usage change regularly
Vaccine Information Statements (VISs) that explain the benefits and risks must be given out before vaccine is administered—a federal law!! (http://www.cdc.gov/vaccines/hcp/vis/index.html)
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
21
Available Vaccines by Type
Live attenuated vaccines (See Textbook Table 25-3)
Viral: measles, mumps, rubella, oral polio, vaccinia, yellow fever, varicella
Bacterial: BCG (Bacille Calmette-Guérin)
Recombinant: oral typhoid
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
22
Available Vaccines by Type (Cont.)
Inactivated vaccines (See Textbook Table 25-3)
Viral: influenza, polio, rabies, and hepatitis A
Bacterial: typhoid, cholera, and plague
Subunit (fractional): influenza, acellular pertussis, typhoid Vi and Lyme disease
Toxoid: diphtheria and tetanus
Recombinant: hepatitis B
Conjugate polysaccharide: Haemophilus influenzae type B and pneumococcal 7-valent
Pure polysaccharide: Pneumococcal 23-valent, meningococcal, and Haemophilus influenzae type b
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
23
Recommended Vaccine Schedules (Textbook Box 25-6)
Children/adolescents
http://www.cdc.gov/vaccines/schedules/hcp/child-adolescent.html
Adults
http://www.cdc.gov/vaccines/schedules/hcp/adult.html
Travelers
http://wwwnc.cdc.gov/travel/destinations/list
Pregnant women
www.cdc.gov/vaccines/pubs/preg-guide.htm
Health care workers
www.cdc.gov/vaccines/spec-grps/hcw.htm
Specific health conditions
www.cdc.gov/vaccines/spec-grps/conditions.htm
Other special groups
www.cdc.gov/vaccines/spec-grps/default.htm
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
24
Vaccine Storage, Transport, and Handling
Cold chain
Routes of administration, dosage, and sites
Proper timing and spacing
Hypersensitivity and contraindications
Documentation
Vaccine safety and reporting of adverse events and vaccine-related injuries (VAERS)
Vaccine needs for special groups
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
25
Prevention of Communicable Diseases
Primary prevention
To prevent transmission of an infectious agent and to prevent pathology in the person exposed to an infection
Secondary prevention
Activities to detect early and effectively treat persons who are infected
Tertiary prevention
Caring for persons with an infectious disease to ensure that they are cured or that their quality of life is maintained
Copyright © 2015, 2011, 2007, 2001, 1997, 1993 by Saunders, an imprint of Elsevier Inc.
26
The post Biological and epidemiological principles appeared first on Infinite Essays.
Biological and epidemiological principles
"If this is not the paper you were searching for, you can order your 100% plagiarism free, professional written paper now!"
