This document provides definitions and concepts related to communicable disease epidemiology. It defines epidemiology as the study of health-related states and events in populations. The epidemiologic triad shows the interaction between host, agent, and environment. A communicable disease is an illness transmitted directly or indirectly between humans, animals, or the environment. Studying communicable disease epidemiology is important for understanding changes in disease patterns, discovering new infections, and investigating chronic disease origins. Key concepts covered include reservoirs, modes of transmission, susceptible hosts, outbreak definitions, and the chain of infection.
infectious-diseases -lec 1.pptGangrene is a clinical condition of ischemic an...RabeaDia
Gangrene is a clinical condition of ischemic and necrotic tissue, often circumferential around a digit or extremity. It is identified by discolored or black tissue and associated sloughing of natural tissue planes. The three main types of gangrene are wet gangrene, dry gangrene, and gas gangrene.Aug 7, 2023
infectious-diseases -lec 1.pptGangrene is a clinical condition of ischemic an...RabeaDia
Gangrene is a clinical condition of ischemic and necrotic tissue, often circumferential around a digit or extremity. It is identified by discolored or black tissue and associated sloughing of natural tissue planes. The three main types of gangrene are wet gangrene, dry gangrene, and gas gangrene.Aug 7, 2023
Module 5 Case Assignment Pertussis (Whooping Cough)TasksPart .docxadelaidefarmer322
Module 5 Case Assignment:
Pertussis (Whooping Cough)
Tasks
Part A: In one page maximum
Briefly describe the disease: Pertussis in terms of its infectivity, pathogenicity, and virulence.
Identify any reservoir(s), and mode(s) of transmission
Part B: (1-2 pages)
Weighing the benefits and the risks, take a clear position on whether you feel vaccination programs for Pertussis (whooping cough) should be expanded in your current community. Explain factors that went into your decision.
HELPING REFERENCES
U.S. Food & Drug Administration, Center for Food Safety & Applied Nutrition (n.d.) Bad Bug Book. Retrieved February 21, 2013 from
http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/default.htm
FAO. Epidemiology: some basic concepts and definitions. Retrieved February 21, 2013 from
http://www.fao.org/wairdocs/ILRI/x5436E/x5436e04.htm
Centers for Disease Control and Prevention (2004). How to Investigate an Outbreak. Retrieved February 21, 2013 from
http://www.cdc.gov/excite/classroom/outbreak/steps.htm
Aschengrau A, Seage GR (2003). Chapter 6: Overview of Epidemiologic Study Designs. Essentials of Epidemiology in Public Health, Boston: Jones & Bartlett Publishers. Retrieved February 21, 2013 at:
http://publichealth.jbpub.com/aschengrau/Aschengrau06.pdf
Cosio G (2005). Epidemiological Overview of Tuberculosis [Presentation]. Retrieved February 21, 2013 from
www.paho.org/cdmedia/dpccd01/Presentations/Day1/EPIDEMIOLOGICAL%20OVERVIEW%20OF%20TUBERCULOSIS%202.ppt
Optional Readings
Long SG, DuPont HL, Gaul L, Arafat RR, Selwyn BJ, Rogers J, et al. (2007). Pulsed-field gel electrophoresis for
Salmonella
infection surveillance, Texas, USA. Emerg Infect Dis [serial on the Internet]. Retrieved fro
http://www.cdc.gov/EID/content/16/6/983.htm
READ:
Variations in Severity of Illness
The severity of an illness may be measured by the case fatality rate or the proportion of surviving patients with complications. The
case fatality rate
is defined as the number of deaths from a particular disease divided by the number of clinically apparent cases of that disease.
An infectious disease may have a wide variety of clinical symptoms, ranging from no symptoms to severe clinical illness or death. Diseases such as tuberculosis have a high proportion of asymptomatic individuals (low pathogenicity), while diseases such as measles have a high proportion of symptomatic infections and a small percent of severe or fatal illness. Diseases such as the African hemorrhagic fevers caused by Marburg and Ebola virus are very severe and usually fatal. For diseases with low pathogenicity, only a small fraction of cases are often diagnosed and reported. Control measures should be directed toward all infections capable of being transmitted to others, not just the symptomatic cases.
From a public health perspective, diseases of high incidence and lesser severity may be considered a more serious problem becaus.
zoonoses and its classification on basis of typesNabeel805998
This presentation contains a compression data on the Zoonosis, its types and classification. Along with it aslo contains data on bacterial and viral diseases that are zoonotic. There are terminologies related to epidemiology.
zoonoses and its classification on basis of typesNabeel805998
This presentation contains a compression data on the Zoonosis, its types and classification. Along with it aslo contains data on bacterial and viral diseases that are zoonotic. There are terminologies related to epidemiology.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Module 5 Case Assignment Pertussis (Whooping Cough)TasksPart .docxadelaidefarmer322
Module 5 Case Assignment:
Pertussis (Whooping Cough)
Tasks
Part A: In one page maximum
Briefly describe the disease: Pertussis in terms of its infectivity, pathogenicity, and virulence.
Identify any reservoir(s), and mode(s) of transmission
Part B: (1-2 pages)
Weighing the benefits and the risks, take a clear position on whether you feel vaccination programs for Pertussis (whooping cough) should be expanded in your current community. Explain factors that went into your decision.
HELPING REFERENCES
U.S. Food & Drug Administration, Center for Food Safety & Applied Nutrition (n.d.) Bad Bug Book. Retrieved February 21, 2013 from
http://www.fda.gov/Food/FoodSafety/FoodborneIllness/FoodborneIllnessFoodbornePathogensNaturalToxins/BadBugBook/default.htm
FAO. Epidemiology: some basic concepts and definitions. Retrieved February 21, 2013 from
http://www.fao.org/wairdocs/ILRI/x5436E/x5436e04.htm
Centers for Disease Control and Prevention (2004). How to Investigate an Outbreak. Retrieved February 21, 2013 from
http://www.cdc.gov/excite/classroom/outbreak/steps.htm
Aschengrau A, Seage GR (2003). Chapter 6: Overview of Epidemiologic Study Designs. Essentials of Epidemiology in Public Health, Boston: Jones & Bartlett Publishers. Retrieved February 21, 2013 at:
http://publichealth.jbpub.com/aschengrau/Aschengrau06.pdf
Cosio G (2005). Epidemiological Overview of Tuberculosis [Presentation]. Retrieved February 21, 2013 from
www.paho.org/cdmedia/dpccd01/Presentations/Day1/EPIDEMIOLOGICAL%20OVERVIEW%20OF%20TUBERCULOSIS%202.ppt
Optional Readings
Long SG, DuPont HL, Gaul L, Arafat RR, Selwyn BJ, Rogers J, et al. (2007). Pulsed-field gel electrophoresis for
Salmonella
infection surveillance, Texas, USA. Emerg Infect Dis [serial on the Internet]. Retrieved fro
http://www.cdc.gov/EID/content/16/6/983.htm
READ:
Variations in Severity of Illness
The severity of an illness may be measured by the case fatality rate or the proportion of surviving patients with complications. The
case fatality rate
is defined as the number of deaths from a particular disease divided by the number of clinically apparent cases of that disease.
An infectious disease may have a wide variety of clinical symptoms, ranging from no symptoms to severe clinical illness or death. Diseases such as tuberculosis have a high proportion of asymptomatic individuals (low pathogenicity), while diseases such as measles have a high proportion of symptomatic infections and a small percent of severe or fatal illness. Diseases such as the African hemorrhagic fevers caused by Marburg and Ebola virus are very severe and usually fatal. For diseases with low pathogenicity, only a small fraction of cases are often diagnosed and reported. Control measures should be directed toward all infections capable of being transmitted to others, not just the symptomatic cases.
From a public health perspective, diseases of high incidence and lesser severity may be considered a more serious problem becaus.
zoonoses and its classification on basis of typesNabeel805998
This presentation contains a compression data on the Zoonosis, its types and classification. Along with it aslo contains data on bacterial and viral diseases that are zoonotic. There are terminologies related to epidemiology.
zoonoses and its classification on basis of typesNabeel805998
This presentation contains a compression data on the Zoonosis, its types and classification. Along with it aslo contains data on bacterial and viral diseases that are zoonotic. There are terminologies related to epidemiology.
Title: Sense of Smell
Presenter: Dr. Faiza, Assistant Professor of Physiology
Qualifications:
MBBS (Best Graduate, AIMC Lahore)
FCPS Physiology
ICMT, CHPE, DHPE (STMU)
MPH (GC University, Faisalabad)
MBA (Virtual University of Pakistan)
Learning Objectives:
Describe the primary categories of smells and the concept of odor blindness.
Explain the structure and location of the olfactory membrane and mucosa, including the types and roles of cells involved in olfaction.
Describe the pathway and mechanisms of olfactory signal transmission from the olfactory receptors to the brain.
Illustrate the biochemical cascade triggered by odorant binding to olfactory receptors, including the role of G-proteins and second messengers in generating an action potential.
Identify different types of olfactory disorders such as anosmia, hyposmia, hyperosmia, and dysosmia, including their potential causes.
Key Topics:
Olfactory Genes:
3% of the human genome accounts for olfactory genes.
400 genes for odorant receptors.
Olfactory Membrane:
Located in the superior part of the nasal cavity.
Medially: Folds downward along the superior septum.
Laterally: Folds over the superior turbinate and upper surface of the middle turbinate.
Total surface area: 5-10 square centimeters.
Olfactory Mucosa:
Olfactory Cells: Bipolar nerve cells derived from the CNS (100 million), with 4-25 olfactory cilia per cell.
Sustentacular Cells: Produce mucus and maintain ionic and molecular environment.
Basal Cells: Replace worn-out olfactory cells with an average lifespan of 1-2 months.
Bowman’s Gland: Secretes mucus.
Stimulation of Olfactory Cells:
Odorant dissolves in mucus and attaches to receptors on olfactory cilia.
Involves a cascade effect through G-proteins and second messengers, leading to depolarization and action potential generation in the olfactory nerve.
Quality of a Good Odorant:
Small (3-20 Carbon atoms), volatile, water-soluble, and lipid-soluble.
Facilitated by odorant-binding proteins in mucus.
Membrane Potential and Action Potential:
Resting membrane potential: -55mV.
Action potential frequency in the olfactory nerve increases with odorant strength.
Adaptation Towards the Sense of Smell:
Rapid adaptation within the first second, with further slow adaptation.
Psychological adaptation greater than receptor adaptation, involving feedback inhibition from the central nervous system.
Primary Sensations of Smell:
Camphoraceous, Musky, Floral, Pepperminty, Ethereal, Pungent, Putrid.
Odor Detection Threshold:
Examples: Hydrogen sulfide (0.0005 ppm), Methyl-mercaptan (0.002 ppm).
Some toxic substances are odorless at lethal concentrations.
Characteristics of Smell:
Odor blindness for single substances due to lack of appropriate receptor protein.
Behavioral and emotional influences of smell.
Transmission of Olfactory Signals:
From olfactory cells to glomeruli in the olfactory bulb, involving lateral inhibition.
Primitive, less old, and new olfactory systems with different path
Ethanol (CH3CH2OH), or beverage alcohol, is a two-carbon alcohol
that is rapidly distributed in the body and brain. Ethanol alters many
neurochemical systems and has rewarding and addictive properties. It
is the oldest recreational drug and likely contributes to more morbidity,
mortality, and public health costs than all illicit drugs combined. The
5th edition of the Diagnostic and Statistical Manual of Mental Disorders
(DSM-5) integrates alcohol abuse and alcohol dependence into a single
disorder called alcohol use disorder (AUD), with mild, moderate,
and severe subclassifications (American Psychiatric Association, 2013).
In the DSM-5, all types of substance abuse and dependence have been
combined into a single substance use disorder (SUD) on a continuum
from mild to severe. A diagnosis of AUD requires that at least two of
the 11 DSM-5 behaviors be present within a 12-month period (mild
AUD: 2–3 criteria; moderate AUD: 4–5 criteria; severe AUD: 6–11 criteria).
The four main behavioral effects of AUD are impaired control over
drinking, negative social consequences, risky use, and altered physiological
effects (tolerance, withdrawal). This chapter presents an overview
of the prevalence and harmful consequences of AUD in the U.S.,
the systemic nature of the disease, neurocircuitry and stages of AUD,
comorbidities, fetal alcohol spectrum disorders, genetic risk factors, and
pharmacotherapies for AUD.
Report Back from SGO 2024: What’s the Latest in Cervical Cancer?bkling
Are you curious about what’s new in cervical cancer research or unsure what the findings mean? Join Dr. Emily Ko, a gynecologic oncologist at Penn Medicine, to learn about the latest updates from the Society of Gynecologic Oncology (SGO) 2024 Annual Meeting on Women’s Cancer. Dr. Ko will discuss what the research presented at the conference means for you and answer your questions about the new developments.
Explore natural remedies for syphilis treatment in Singapore. Discover alternative therapies, herbal remedies, and lifestyle changes that may complement conventional treatments. Learn about holistic approaches to managing syphilis symptoms and supporting overall health.
These simplified slides by Dr. Sidra Arshad present an overview of the non-respiratory functions of the respiratory tract.
Learning objectives:
1. Enlist the non-respiratory functions of the respiratory tract
2. Briefly explain how these functions are carried out
3. Discuss the significance of dead space
4. Differentiate between minute ventilation and alveolar ventilation
5. Describe the cough and sneeze reflexes
Study Resources:
1. Chapter 39, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 34, Ganong’s Review of Medical Physiology, 26th edition
3. Chapter 17, Human Physiology by Lauralee Sherwood, 9th edition
4. Non-respiratory functions of the lungs https://academic.oup.com/bjaed/article/13/3/98/278874
New Directions in Targeted Therapeutic Approaches for Older Adults With Mantl...i3 Health
i3 Health is pleased to make the speaker slides from this activity available for use as a non-accredited self-study or teaching resource.
This slide deck presented by Dr. Kami Maddocks, Professor-Clinical in the Division of Hematology and
Associate Division Director for Ambulatory Operations
The Ohio State University Comprehensive Cancer Center, will provide insight into new directions in targeted therapeutic approaches for older adults with mantle cell lymphoma.
STATEMENT OF NEED
Mantle cell lymphoma (MCL) is a rare, aggressive B-cell non-Hodgkin lymphoma (NHL) accounting for 5% to 7% of all lymphomas. Its prognosis ranges from indolent disease that does not require treatment for years to very aggressive disease, which is associated with poor survival (Silkenstedt et al, 2021). Typically, MCL is diagnosed at advanced stage and in older patients who cannot tolerate intensive therapy (NCCN, 2022). Although recent advances have slightly increased remission rates, recurrence and relapse remain very common, leading to a median overall survival between 3 and 6 years (LLS, 2021). Though there are several effective options, progress is still needed towards establishing an accepted frontline approach for MCL (Castellino et al, 2022). Treatment selection and management of MCL are complicated by the heterogeneity of prognosis, advanced age and comorbidities of patients, and lack of an established standard approach for treatment, making it vital that clinicians be familiar with the latest research and advances in this area. In this activity chaired by Michael Wang, MD, Professor in the Department of Lymphoma & Myeloma at MD Anderson Cancer Center, expert faculty will discuss prognostic factors informing treatment, the promising results of recent trials in new therapeutic approaches, and the implications of treatment resistance in therapeutic selection for MCL.
Target Audience
Hematology/oncology fellows, attending faculty, and other health care professionals involved in the treatment of patients with mantle cell lymphoma (MCL).
Learning Objectives
1.) Identify clinical and biological prognostic factors that can guide treatment decision making for older adults with MCL
2.) Evaluate emerging data on targeted therapeutic approaches for treatment-naive and relapsed/refractory MCL and their applicability to older adults
3.) Assess mechanisms of resistance to targeted therapies for MCL and their implications for treatment selection
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Ve...kevinkariuki227
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
TEST BANK for Operations Management, 14th Edition by William J. Stevenson, Verified Chapters 1 - 19, Complete Newest Version.pdf
These lecture slides, by Dr Sidra Arshad, offer a quick overview of physiological basis of a normal electrocardiogram.
Learning objectives:
1. Define an electrocardiogram (ECG) and electrocardiography
2. Describe how dipoles generated by the heart produce the waveforms of the ECG
3. Describe the components of a normal electrocardiogram of a typical bipolar leads (limb II)
4. Differentiate between intervals and segments
5. Enlist some common indications for obtaining an ECG
Study Resources:
1. Chapter 11, Guyton and Hall Textbook of Medical Physiology, 14th edition
2. Chapter 9, Human Physiology - From Cells to Systems, Lauralee Sherwood, 9th edition
3. Chapter 29, Ganong’s Review of Medical Physiology, 26th edition
4. Electrocardiogram, StatPearls - https://www.ncbi.nlm.nih.gov/books/NBK549803/
5. ECG in Medical Practice by ABM Abdullah, 4th edition
6. ECG Basics, http://www.nataliescasebook.com/tag/e-c-g-basics
2. Objectives
Definition of epidemiology
The epidemiologic triad
Definition of communicable diseases
Importance of studying
communicable diseases epidemiology
Terminology
Dynamics of disease transmission
(chain of infection):
– Human reservoir or source
– Modes of transmission
– Susceptible host
3. Definition of Epidemiology
Epidemiology is the study of the
distribution and determinants of
health-related states and events
in populations, and the
application of this study to
control health problems (Last,
1983).
6. Definition of communicable
diseases
A communicable disease is an illness
due to a specific infectious
(biological) agent or its toxic
products capable of being directly or
indirectly transmitted from man to
man, from animal to man, from
animal to animal, or from the
environment (through air, water,
food, etc..) to man.
7. Importance of Studying Communicable
Diseases Epidemiology
Changes of the pattern of infectious
diseases
Discovery of new infections
The possibility that some chronic
diseases have an infective origin.
9. Terminology and Definitions (cont.)
Virulence
Reproductive rate of
infection
Host
Vector (source)
Reservoir
Incubation period
Infectivity period
Serial interval
Latent period
Transmission
Probability ratio
10. Infection
Infection is the entry and development or
multiplication of an infectious agent in the
body of man or animals. An infection does
not always cause illness.
There are several levels of infection
(Gradients of infection):
– Colonization (S. aureus in skin and normal
nasopharynx)
– Subclinical or inapparent infection (polio)
– Latent infection (virus of herpes simplex)
– Manifest or clinical infection
11. contamination
The presence of an infectious agent
on a body surface, on or in clothes,
beddings, toys, surgical instruments
or dressings, or other articles or
substances including water and food
12. Infestation
It is the lodgment, development and
reproduction of arthropods on the
surface of the body or in the
clothing, e.g. lice, itch mite. This
term could be also used to describe
the invasion of the gut by parasitic
worms, e.g. ascariasis.
13. Contagious disease
A contagious disease is the one that
is transmitted through contact.
Examples include scabies, trachoma,
STD and leprosy.
14. Host
A person or an animal that affords
subsistence or lodgement to an
infectious agent under natural
conditions. Types include: an
obligate host, definitive (primary)
host, intermediate host and a
transport host.
15. Vector of infection
An insect or any living carrier that
transports an infectious agent from
an infected individual or its wastes to
a susceptible individual or its food or
immediate surroundings. Both
biological and mechanical
transmissions are encountered.
16. Reservoir
Any person, animal, arthropod,
plant, soil, or substance, or a
combination of these, in which an
infectious agent normally lives and
multiplies, on which it depends
primarily for survival, and where it
reproduces itself in such a manner
that it can be transmitted to a
susceptible host. It is the natural
habitat of the infectious agent.
17. Incidence and prevalence of
infectious diseases
Incidence of an infectious disease: number of
new cases in a given time period expressed as
percent infected per year (cumulative incidence)
or number per person time of observation
(incidence density).
Prevalence of an infectious disease: number of
cases at a given time expressed as a percent at a
given time. Prevalence is a product of incidence x
duration of disease, and is of little interest if an
infectious disease is of short duration (i.e.
measles), but may be of interest if an infectious
disease is of long duration (i.e. chronic hepatitis
B).
18. Epidemic
“The unusual occurrence in a
community of disease, specific health
related behavior, or other health
related events clearly in excess of
expected occurrence”
(epi= upon; demos= people)
Epidemics can occur upon endemic
states too.
19. Endemic
It refers to the constant presence of
a disease or infectious agent within a
given geographic area or population
group. It is the usual or expected
frequency of disease within a
population.
(En = in; demos = people)
20. Hyperendemic and holoendemic
The term “hyperendemic” expresses that
the disease is constantly present at high
incidence and/or prevalence rate and
affects all age groups equally.
The term “holoendemic” expresses a high
level of infection beginning early in life
and 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 (e.g. malaria)
21. Pandemic and Exotic
An epidemic usually affecting a large
proportion of the population, occuring
over a wide geographic area such as a
section of a nation, the entire nation, a
continent or the world, e.g. Influenza
pandemics.
Exotic diseases are those which are
imported into a country in which they do
not otherwise occur, as for example,
rabies in the UK.
22. Sporadic
The word sporadic means “scattered
about”. The cases occur irregularly,
haphazardly from time to time, and
generally infrequently. The cases are few
and separated widely in time and place
that they show no or little connection with
each other, nor a recognizable common
source of infection e.g. polio,
meningococcal meningitis, tetanus….
However, a sporadic disease could be the
starting point of an epidemic when the
conditions are favorable for its spread.
23. Attack rates and primary/secondary
cases
Attack rate: proportion of non-immune
exposed individuals who become clinically
ill.
Primary (index)/secondary cases: The
person who comes into and infects a
population is the primary case. Those who
subsequently contract the infection are
secondary cases. Further spread is
described as "waves" or "generations".
24. Zoonosis, epizootic and enzootic
Zoonosis is an infection that is
transmissible under natural conditions
from vertebrate animals to man, e.g.
rabies, plague, bovine tuberculosis…..
An epizotic is an outbreak (epidemic) of
disease in an animal population, e.g. rift
valley fever.
An Enzotic is an endemic occurring in
animals, e.g. bovine TB.
25. Nosocomial infections
Nosocomial (hospital acquired)
infection is an infection originating in
a patient while in a hospital or
another health care facility. It has to
be a new disorder unrelated to the
patient’s primary condition.
Examples include infection of surgical
wounds, hepatitis B and urinary tract
infetions.
26. Opportunistic infection
This is infection by organisms that
take the opportunity provided by a
defect in host defense (e.g.
immunity) to infect the host and thus
cause disease. For example,
opportunistic infections are very
common in AIDS. Organisms include
Herpes simplex, cytomegalovirus,
M. tuberculosis….
27. Eradication and Elimination
Termination of all transmission of infection by the
extermination of the infectious agent through
surveillance and containment. Eradication is an
absolute process, an “all or none” phenomenon,
restricted to termination of infection from the
whole world.
The term elimination is sometimes used to
describe eradication of a disease from a large
geographic region. Disease which are amenable
to elimination in the meantime are polio, measles
and diphtheria.
28. Reproductive rate of infection:
Reproductive rate of infection: potential
for an infectious disease to spread.
Influential factors include the probability
of transmission between an infected and a
susceptible individual; frequency of
population contact; duration of infection;
virulence of the organism and population
immune proportion .
29. Dynamics of disease Transmission
(Chain of Infection)
Source or Reservoir Modes of transmission Susceptible host
I II III
30. (I): Source or Reservoir
The starting point for the occurrence of a
communicable disease is the existence of a
reservoir or source of infection.
The source of infection is defined as “the person,
animal, object or substance from which an
infectious agent passes or is disseminated to the
host (immediate source). The reservoir is “any
person, animal, arthropod, plant, soil, or
substance, or a combination of these, in which an
infectious agent normally lives and multiplies, on
which it depends primarily for survival, and
where it reproduces itself in such a manner that
it can be transmitted to a susceptible host. It is
the natural habitat of the infectious agent.”
32. Human reservoir
Human reservoir
cases carriers
According to spectrum of disease:
•Clinical cases
(mild/severe-typical/atypical)
•Sub-clinical cases
•Latent infection cases
•Primary case
•Index case
•Secondary cases
Type:
•Incubatory
•Convalescent
•healthy
Duration:
•Temporar
y
•Chronic
Portal of exit:
•Urinary
•Intestinal
•Respiratory
•others
33. Cases
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”
34. Carriers
It occurs either due to inadequate treatment or immune
response, the disease agent is not completely eliminated,
leading to a carrier state.
It is “an infected person or animal that harbors a specific
infectious agent in the absence of discernible (visible)
clinical disease and serves as a potential source of
infection to others.
Three elements have to occur to form a carrier state:
1. The presence in the body of the disease agent.
2. The absence of recognizable symptoms and signs of
disease.
3. The shedding of disease agent in the discharge or
excretions.
35. Animal reservoirs
Zoonosis is an infection that is
transmissible under natural
conditions from vertebrate animals
to man, e.g. rabies, plague, bovine
tuberculosis…..
There are over a 100 zoonotic
diseases that can be conveyed from
animal to man.
36. Reservoir in non-living things
Soil and inanimate matter can also
act as reservoir of infection.
For example, soil may harbor agents
that causes tetanus, anthrax and
coccidiodomycosis.
37. (II): Modes of transmission
Mode of transmission
Direct
transmission
Indirect
transmission
Direct contact
Droplet infection
Contact with soil
Inoculation into skin or mucosa
Trans-placental (vertical)
Vehicle-borne
•
Vector-borne:
•Mechanical
•biological
Air-borne
Fomite-born
Unclean hands
and fingers
propagative
Cyclo-prop.
Cyclo-develop.
38. (III): Susceptible host
An infectious agent seeks a susceptible
host aiming “successful parasitism”.
Four stages are required for successful
parasitism:
1. Portal of entry
2. Site of election inside the body
3. Portal of exit
4. Survival in external environment
39. Virulence and Case Fatality Rate
Virulence: is the degree of pathogenicity; the
disease evoking power of a micro-organism in a
given host. Numerically expressed as the ratio of
the number of cases of overt infection to the total
number infected, as determined by
immunoassay. When death is the only criterion of
severity, this is the case fatality rate.
Case fatality rate for infectious diseases: is
the proportion of infected individuals who die of
the infection. This is a function of the severity of
the infection and is heavily influenced by how
many mild cases are not diagnosed.
40. Serial interval and Infectious period
Serial interval: (the gap in time between
the onset of the primary and the
secondary cases) the interval between
receipt of infection and maximal infectivity
of the host (also called generation time).
Infectious (communicable) period: length
of time a person can transmit disease
(sheds the infectious agent).
41. Incubation and Latent periods
Incubation period: time from exposure to
development of disease. In other words,
the time interval between invasion by an
infectious agent and the appearance of the
first sign or symptom of the disease in
question.
Latent period: the period between
exposure and the onset of infectiousness
(this may be shorter or longer than the
incubation period).
42. Transmission Probability Ratio
(TPR)
TPR is a measure of risk transmission
from infected to susceptible individuals
during a contact.
TPR of differing types of contacts,
infectious agents, infection routes and
strains can be calculated.
There are 4 types of transmission
probabilities.
43. TPR (cont.)
Transmission probabilities:
p00: tp from unvaccinated infective to
unvaccinated susceptible
p01: tp from vaccinated infective to
unvaccinated susceptible
p10: tp from unvaccinated infective to
vaccinated susceptible
p11: tp from vaccinated infective to
vaccinated susceptible
44. TPR (cont.)
To estimate the effect of a vaccine in
reducing susceptibility, compare the ratio
of p10 to p00.
To estimate the effect of a vaccine in
reducing infectiousness, compare the ratio
of p01 to p00.
To estimate the combined effect of a
vaccine, compare the ratio of p11 to p00.