principles of disease and epidemiology · epidemiology • study occurrence of disease and disease...
TRANSCRIPT
![Page 1: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/1.jpg)
Principles of disease and epidemiology
Principles of disease and Principles of disease and epidemiologyepidemiology
ByByDr. Carmen RexachDr. Carmen Rexach
MicrobiologyMicrobiologyMt San Antonio CollegeMt San Antonio College
![Page 2: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/2.jpg)
Definitions• Disease
– Any change from state of health
• Epidemiology– Study of
occurrences and transmission of disease in populations
• Pathogens– Disease causing
organisms
![Page 3: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/3.jpg)
Definitions• Pathology
– Study of disease• Pathogenesis
– How a disease develops
• Infection– Invasion or
colonization of body with pathogenic microorganisms
![Page 4: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/4.jpg)
Normal microbial flora
• Microbes normally present in the body, non-disease producing– Intestinal tract inhabitants– On surface of skin– In oral/urogenital cavities
• Symbiotic relationships– Commensalism– Mutualism– Parasitism
![Page 5: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/5.jpg)
Monogenean parasite of fish
Normal gut flora
![Page 6: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/6.jpg)
Microbial antagonism • Control of growth of harmful bacteria
by presence of normal flora• Competitive inhibition• Production of substances that inhibit
growth of undesirable bacteria– Streptococcus in mouth inhibits growth of
most gram-positive and gram-negative cocci– Bacteriocins produced by E.coli inhibit
growth of pathogenic bacteria
![Page 7: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/7.jpg)
Bacteriocins
![Page 8: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/8.jpg)
Opportunistic organisms• Organisms associated with disease
but not in healthy individuals, under ordinary circumstances, in normal habitat
• Immunocompromised or suppressed– AIDS and Pneumocystis carinii– Fungal infections in feet of diabetics– Transplant recipients on
immunosuppressive drugs
![Page 9: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/9.jpg)
Oral thrushKaposi’s sarcoma
EBV
Leukemiapatient
![Page 10: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/10.jpg)
Cooperation among microorganisms
• Infection with one type of microbe makes it easier to contract particular disease
• Example– Mycoplasma fermentans infection and
HIV– Synergistic relationship = effect of the
two together greater than each as individual
![Page 11: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/11.jpg)
Etiology of infectious disease• Koch’s postulates
– Same pathogen present in every case of disease
– Pathogen isolated from disease host and grown in pure culture
– Pathogen from pure culture must cause disease when introduced into healthy, susceptible lab animal
– Must re-isolate organism and show it to be same as in the original case of disease
![Page 12: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/12.jpg)
Exceptions• Bacterial
– Treponema pallidum– Mycobacterium leprae– Intracellular bacteria (rickettsias)– Legionella spp.
• Viral– Intracellular parasite of cells
• Signs/symptoms– Some very specific to etiologic agent, some general– Some organisms cause multiple symptoms or have
variety of effects on body
![Page 13: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/13.jpg)
Treponema pallidum
![Page 14: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/14.jpg)
Mycobacterium leprae
![Page 15: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/15.jpg)
Staphyloccocus aureus
![Page 16: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/16.jpg)
Infectious disease• Symptoms
– Subjective changes in body function, (pain, nausea)• Signs
– Objective changes in body function, (fever or paralysis)• Syndromes
– Group of signs & symptoms associated with a particular disease
• Communicable disease– Disease which spreads from one host to another, directly
or indirectly• Contagious disease
– Disease easily spread from one host to another, communicable
• Non-communicable disease– Not spread form one host to another, caused by normal
flora or introduced microbes
![Page 17: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/17.jpg)
![Page 18: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/18.jpg)
Classification of infectious disease
• Occurrence of disease• Severity or duration of disease• Extent of host involvement
![Page 19: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/19.jpg)
Occurrence of disease• Incidence
– Percent of new cases in population in given time period• Prevalence
– Percent of individuals having disease in population at specified point in time
• Frequency of occurrence– Sporadic
• only on occasion– Endemic
• constantly present in the population– Epidemic
• infects many people in given area in short time period– Pandemic
• epidemic disease with worldwide occurrence
![Page 20: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/20.jpg)
AIDS incidence AIDS prevalence
![Page 21: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/21.jpg)
Severity or duration of disease• Acute
– Develops rapidly, short duration• Chronic
– Slower development– Less severe reaction – Continual or recurrent in duration
• Subacute– Halfway between acute and chronic
• Latent– Causative agent is inactive for some time, can
become active producing disease symptoms
![Page 22: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/22.jpg)
Extent of host involvement• Local infection
– Infection localized to small area of body• Systemic
– Generalized, spread throughout body• Focal infections
– Spread via circulatory system to other locations• Conditions involving blood
– Bacteremia– Septicemia– Toxemia– Viremia
![Page 23: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/23.jpg)
Extent of host involvement
• Primary infections– Acute infection resulting in initial illness
• Secondary infections– Caused by opportunist after primary
infection• Subclinical infections
– No noticeable disease
![Page 24: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/24.jpg)
Reservoirs• Source of disease organisms
– Human– Animal– Non-living
• Water, soil
![Page 25: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/25.jpg)
Human reservoirs• Some symptomatic• Carriers
– Typhoid Mary• Diseases in which humans are reservoir
– AIDS– Diphtheria– Typhoid– Hepatitis– Gonorrhea– Dysentery– Streptococcus
![Page 26: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/26.jpg)
Animal reservoirs• Sylvatic/domestic• Zoonoses
– Transmission• Direct contact with infected animal (rabies)• Direct contact with waste of infected animal
(HVPS)• Contaminated food/water (Giardiasis)• Contaminated furs/hides, feathers
(Tularemia)• Consumption of infected animal parts (BSE)• Insect vectors (WEE, dengue, malaria, yellow
fever)
![Page 27: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/27.jpg)
3 routes of disease transmission
• Contact• Transmission by vehicle• vectors
![Page 28: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/28.jpg)
Contact
• Direct contact transmission– Person to person, animal to person transmission– Physical contact between source and suspect
host• Indirect contact transmission
– Agent of disease from reservoir to suspect host via fomite (non-living object involved with spread of disease)
• Droplet transmission– Microbes spread by droplet nuclei (mucus
droplets), sneeze, cough, talk
![Page 29: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/29.jpg)
![Page 30: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/30.jpg)
Transmission by vehicle• Transmission of disease agents by medium– Water, food, air, blood, body fluids, IV
drugs, etc.• Waterborne
– Usually contaminated with untreated or poorly treated sewage
• Foodborne– Incompletely cooked, poor refrigeration,
unsanitary conditions
![Page 31: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/31.jpg)
Transmission by vehicle
• Airborne• Can travel in dust more than one
meter from reservoir to host• Examples: fungal spores associated
with coccidiodomycoses, blastomycosis, histoplasmosis
![Page 32: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/32.jpg)
Distribution of C. immitis in US
![Page 33: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/33.jpg)
Vectors• Usually arthropods carry organisms
from one host to another• Mechanical transmission
– Passive transport on insect body part• Biological transmission
– Pathogen acquired in blood meal– Multiplies in vector– Transmitted to host in bite, defecation,
vomiting while biting– Examples: Yersinia pestis, Plasmodium
spp., Rickettsia prowazekii
![Page 34: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/34.jpg)
![Page 35: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/35.jpg)
Portals of exit
• Usually connected with infected part of body
• Most common– Respiratory– Gi tracts– Urogenital tracts
• Skin or wound infections
![Page 36: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/36.jpg)
Factors influencing emerging infectious diseases
• Movement of diseases from one species to another– Changes in susceptibility of new host– Changes in pathogen which change or increase
host range• Increase in human population• Increase in travel• Encroachment of humans into undeveloped
areas• Antibiotic resistance
![Page 37: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/37.jpg)
Nosocomial infections
• Infections acquired in hospital• CDC attributes 20,000 deaths
annually– Microbes– Compromised host status– Chain of transmission
![Page 38: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/38.jpg)
Microbes
• Primarily opportunists• Antibiotic resistant strains• Selection for more resistant strains
by wide use of disinfectants– Ex) Pseudomonas
![Page 39: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/39.jpg)
Compromised host• Impaired resistance due to disease,
therapy, burns• Two main conditions
– Broken skin– Suppressed immune system
• Invasive procedures– Catheterization– Tracheotomy– Corticosteroids for transplantation– Treatment of autoimmune disease
![Page 40: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/40.jpg)
Chain of transmission
• Direct contact between patients and hospital personnel
• Indirect– Fomites– Hospital ventilation, etc
![Page 41: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/41.jpg)
How to control infections?
• Hand washing• Aseptic technique• Education• Isolation of contagious patients• Careful administration of antibiotics• Public health recommendations
![Page 42: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/42.jpg)
Factors that predispose to disease
• Genetics• Gender• Occupation• Climate• Weather• Host health status• Age• Nutritional status• Life style• Emotional condition
![Page 43: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/43.jpg)
Disease DevelopmentIncubation Prodrome
Illness
Convalescence
Decline
Death
![Page 44: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/44.jpg)
Development of disease• Incubation
– Time between initial infection and first appearance of signs/symptoms
– Varies with virulence of organism, specific microbe involved, microbe titer, host resistance
• Prodromal period– Not in all diseases, early mild symptoms
![Page 45: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/45.jpg)
Development of disease• Illness
– Most acute state of disease, signs and symptoms apparent
– Two outcomes: immune system intervention = decline of disease; success of pathogen = death
• Decline– Signs and symptoms subside,
susceptibility to secondary disease• Convalescence
– Return of body to pre-disease state
![Page 46: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/46.jpg)
epidemiology
• Study occurrence of disease and disease transmission in populations– Etiology, disease patterns, contributing factors
• Results used in public health to develop methods of disease prevention– Also measure effectiveness of public health
program– Assesses effectiveness of clinical procedures
![Page 47: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/47.jpg)
History of epidemiology
• John Snow and Cholera epidemic in London 1854
![Page 48: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/48.jpg)
Map showing Cases of cholera
![Page 49: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/49.jpg)
Broadstreet pump
![Page 50: Principles of disease and epidemiology · epidemiology • Study occurrence of disease and disease transmission in populations – Etiology, disease patterns, contributing factors](https://reader030.vdocuments.us/reader030/viewer/2022040514/5e6d3a54a363327f9a6da881/html5/thumbnails/50.jpg)
Types• Descriptive
– Retrospective analysis about occurrence of disease so that it can be described
• Analytical– Analysis to determine probable cause
• Case-control studies• Cohort studies
• Experimental– Develop and conduct experiments to test
hypotheses on groups of people– Ex) drug efficacy trials