This document discusses epidemiology, which is the study of disease patterns in populations. It defines key epidemiology terms like morbidity, prevalence, and mortality rates. The document also outlines the cycle of microbial disease, from the reservoir of an infectious agent to transmission between hosts through various routes. It describes factors that influence disease epidemiology, like dose, incubation period, and population characteristics. The roles and objectives of epidemiologists in identifying disease causes, risks, and appropriate control measures are also covered.
Airborne disease can spread when people with certain infections cough, sneeze, or talk, spewing nasal and throat secretions into the air. Some viruses or bacteria take flight and hang in the air or land on other people or surfaces.
When you breathe in airborne pathogenic organisms, they take up residence inside you. You can also pick up germs when you touch a surface that harbors them, and then touch your own eyes, nose, or mouth.
Because these diseases travel in the air, they’re hard to control. Keep reading to learn more about the common types of airborne diseases and what you can do to protect yourself from catching them.
Infectious diseases are mainly caused by
microbes.
These are small microorganisms which are
invisible with the naked eye.
They mainly include bacteria, virus, fungi
and parasites.
The symptoms caused by infection depends
on
the location.
Nature of the infection
Type of the microbe
Airborne disease can spread when people with certain infections cough, sneeze, or talk, spewing nasal and throat secretions into the air. Some viruses or bacteria take flight and hang in the air or land on other people or surfaces.
When you breathe in airborne pathogenic organisms, they take up residence inside you. You can also pick up germs when you touch a surface that harbors them, and then touch your own eyes, nose, or mouth.
Because these diseases travel in the air, they’re hard to control. Keep reading to learn more about the common types of airborne diseases and what you can do to protect yourself from catching them.
Infectious diseases are mainly caused by
microbes.
These are small microorganisms which are
invisible with the naked eye.
They mainly include bacteria, virus, fungi
and parasites.
The symptoms caused by infection depends
on
the location.
Nature of the infection
Type of the microbe
Molecular epidemiology is an emerging branch of epidemiology developed by merging molecular biology into epidemiological studies. Molecular epidemiology studies identify infectious diseases’ causation and pathogenesis and unravel infectious agents’ sources, reservoirs, circulation pattern, transmission pattern, transmission probability, and transmission order. Molecular epidemiology, an area of epidemiology that is somewhat ambiguous, encompasses utilization of biomarkers and genetics as tools to define both exposures (factors that are inherited) and outcomes (factors that are acquired). In last few decades, it has grown extensively to help to understand of disease ecology, in planning disease control, and in drafting health policies.
A presentation on food poisoning (bacterial and mycotoxins): Definition, causative agents, pathogenesis, clinical features and laboratory diagnosis of food poisoning.
It gives all the important definitions used in infectious disease epidemiology and continues to elaborate on dynamics of disease transmission followed by prevention and control of infectious diseases.
Development over the centuries of Human Civilization concepts of disease causation remained transforming and still not reached the perfection.
Pre-modern era theories of Disease causation: Religions often attributed disease outbreaks or other misfortunes to divine retribution - punishment for mankind's sins.
and imbalance among four vital "humors“ within us. Hippocrates; Yellow Bile, Black Bile, Phlegm and Blood
Miasma Theory: 500 BC Miasmas are poisonous emanations from putrefying carcasses, vegetables, molds and also the invisible particles. This theory led to explanation of several outbreaks of cholera, plague and malaria (Mal-aria= bad air).
Fracastoro's contagion theory of disease (1546)
Germ theory: Louis Pasteur , Lister and others introduced the germ theory in 1878. In 1890 Robert Koch proposed specific criteria that should be met before concluding that a disease was caused by a particular bacterium. Only single germ is responsible for causation of a specific disease.
Webs of Causation: Epidemiological concept
Molecular epidemiology is an emerging branch of epidemiology developed by merging molecular biology into epidemiological studies. Molecular epidemiology studies identify infectious diseases’ causation and pathogenesis and unravel infectious agents’ sources, reservoirs, circulation pattern, transmission pattern, transmission probability, and transmission order. Molecular epidemiology, an area of epidemiology that is somewhat ambiguous, encompasses utilization of biomarkers and genetics as tools to define both exposures (factors that are inherited) and outcomes (factors that are acquired). In last few decades, it has grown extensively to help to understand of disease ecology, in planning disease control, and in drafting health policies.
A presentation on food poisoning (bacterial and mycotoxins): Definition, causative agents, pathogenesis, clinical features and laboratory diagnosis of food poisoning.
It gives all the important definitions used in infectious disease epidemiology and continues to elaborate on dynamics of disease transmission followed by prevention and control of infectious diseases.
Development over the centuries of Human Civilization concepts of disease causation remained transforming and still not reached the perfection.
Pre-modern era theories of Disease causation: Religions often attributed disease outbreaks or other misfortunes to divine retribution - punishment for mankind's sins.
and imbalance among four vital "humors“ within us. Hippocrates; Yellow Bile, Black Bile, Phlegm and Blood
Miasma Theory: 500 BC Miasmas are poisonous emanations from putrefying carcasses, vegetables, molds and also the invisible particles. This theory led to explanation of several outbreaks of cholera, plague and malaria (Mal-aria= bad air).
Fracastoro's contagion theory of disease (1546)
Germ theory: Louis Pasteur , Lister and others introduced the germ theory in 1878. In 1890 Robert Koch proposed specific criteria that should be met before concluding that a disease was caused by a particular bacterium. Only single germ is responsible for causation of a specific disease.
Webs of Causation: Epidemiological concept
1. 1st GNM Community H Nsg - Unit 4 Epidemiology.pptxthiru murugan
Community Health Nursing IEpidemiology
By,
Thiru murugan
UNIT-IV: Principles of Epidemiology and Epidemiological methods:
Definition and aims of epidemiology, communicable and non-communicable diseases.
Basic tools of measurement in epidemiology
Uses of epidemiology
Disease cycle
Spectrum of disease
Levels of prevention of disease.
Disease transmission – direct and indirect.
Immunizing agents, immunization and national immunization schedule.
Control of infectious diseases.
Disinfection
Epidemiology:
Introduction: Epidemiology is derived from Greek word “epidemic”
EPI – up on,
DEMOS – people;
LOGOS – study.
Epidemiology means the study of disease in human population.
Definition: “epidemiology is defined as the study of the distribution and determinants of diseases or health problems”.
Terminologies used in epidemiology:
Infection: the entry and multiplication of an infectious agent in the body of man or animal.
Endemic: the constant presence of a disease in particular area or population. Ex- malaria, dengue, chikungunya.
Epidemic: an out break of disease from one area to other area in a community. Ex - cholera, polio, small pox
Sporadic: refers to a disease that occurs infrequently and irregularly. Ex - Tetanus, rabies, and plague.
Pandemic: a disease which spreads from country to country or over the whole world. Ex - swine flu, HIV, COVID – 19.
Zoonosis: diseases or infections transmitted from animals to men. Ex - rabies.
Incubation period: this is the time interval between the entry of the disease agent into the body and the appearance of first sign & symptom of the disease.
Carrier: a person who harbors or carry the disease agent with or without having any outward signs and symptoms.
Isolation: a separation of a person with infectious disease (communicable disease) from contact with other human beings to avoid spread of disease.
Quarantine: a quarantine is a restriction on the movement of people, animals and goods which is intended to prevent the spread of disease
Pathogenicity: ability to cause the disease.
Contagious: a disease that is transmitted through contact.
Reservoir: the habitat ( place for living) where an infectious agent living, grows and multiplies.
Virulence: measure the severity of disease.
Fomites: inanimate articles other than food or water contaminated by the infectious discharges.
Vector: usually an arthropod eg. Mosquito which transfers an infectious agent from an infected person to a healthy person.
Aims
To describe the distribution and size of disease problems in human
To identify the etiological factors.
To provide the data (information) essential to the preparation) implementation (providing) & evaluation (checking the outcome).
Communicable and non-communicable diseases:
Communicable diseases are diseases that spread from person to person. Ex - polio, typhoid, chickenpox, TB,AIDS
Non-communicable disease (NCD) are disease that is not spread from one person to another. Ex - most heart disease
2nd year BSc Nursing - Unit- 3 BSc CHN_-Epidemiology.pptxthiru murugan
2nd Year B.Sc Nursing Community Health Nursing – IEPIDEMIOLOGY
By,
M. Thiru Murugan
UNIT-III: EPIDEMIOLOGY:
Definition, concept, aims, scope, uses and terminology used in epidemiology
Dynamics of disease transmission : epidemiological triad
Morbidity and mortality : measurements
Levels of prevention
Methods of epidemiology:
Descriptive
Analytical: Epidemic investigation
Experimental
Epidemiology
INTRODUCTION: Epidemiology is derived from Greek word “epidemic”
EPI – up on, DEMOS – people; LOGOS – study. Epidemiology means the study of disease in human population.
DEFINITION: “epidemiology is defined as the study of the distribution and determinants of health related states or events in specified populations and the application of this study to control the health problems”.
Concepts Basic to Epidemiology:
Host, Agent, and Environment Model:
Host: The host is a susceptible human or animal who harbors and nourishes a disease causing agent. Many physical, psychological, and lifestyle factors influence the host's susceptibility and response to an agent.
Concepts Basic to Epidemiology:
Agent: An agent is a factor that causes to a health problem or condition.
Causative agents can be Biological, Physical, Psychological, Economical, Nutritional, Environmental etc..
Concepts Basic to Epidemiology:
Environment: The environment refers to all the external factors surrounding the host that might influence vulnerability or resistance.
The physical environment
The psychosocial environment
AIMS OF EPIDEMIOLOGY
Aims:
to describe the distribution and size of disease problems in human population.
to identify the etiological factors.
to provide the data essential to the planning, implementation and evaluation.
SCOPE OF EPIDEMIOLOGY
I. According To Disease Group:
Infectious Disease Epidemiology
Cardio Vascular Epidemiology
Cancer Epidemiology
II. According To Group Of Factors
Nutritive Epidemiology
Reproductive Epidemiology
Environmental Epidemiology
Clinical Epidemiology
Molecular Epidemiology
Genetic Epidemiology
Computational Epidemiology
USES OF EPIDEMIOLOGY
Identify the causes of diseases.
Helps to describe the health status of the population.
Control the disease transmission.
Planning, implementing and evaluating health programmes on evidence basis.
TERMINOLOGIES USED IN EPIDEMIOLOGY
INFECTION: The entry and development or multiplication of an infectious agent in the body of man or animal.
ENDEMIC: The constant presence of a disease or infectious agent within a given geographical area or population group, without importation from outside.
EPIDEMIC: an out break of disease in a community in excess of normal expectation and derived from a common or propagated source.
SPORADIC: The cases occurs irregularly, haphazardly from time to time and generally infrequently.
TERMINOLOGIES USED IN EPIDEMIOLOGY
PANDEMIC: An epidemic which spreads from country to country or over the whole world.
ZOONOSES: Diseases or infections which are natu
Couples presenting to the infertility clinic- Do they really have infertility...Sujoy Dasgupta
Dr Sujoy Dasgupta presented the study on "Couples presenting to the infertility clinic- Do they really have infertility? – The unexplored stories of non-consummation" in the 13th Congress of the Asia Pacific Initiative on Reproduction (ASPIRE 2024) at Manila on 24 May, 2024.
MANAGEMENT OF ATRIOVENTRICULAR CONDUCTION BLOCK.pdfJim Jacob Roy
Cardiac conduction defects can occur due to various causes.
Atrioventricular conduction blocks ( AV blocks ) are classified into 3 types.
This document describes the acute management of AV block.
Lung Cancer: Artificial Intelligence, Synergetics, Complex System Analysis, S...Oleg Kshivets
RESULTS: Overall life span (LS) was 2252.1±1742.5 days and cumulative 5-year survival (5YS) reached 73.2%, 10 years – 64.8%, 20 years – 42.5%. 513 LCP lived more than 5 years (LS=3124.6±1525.6 days), 148 LCP – more than 10 years (LS=5054.4±1504.1 days).199 LCP died because of LC (LS=562.7±374.5 days). 5YS of LCP after bi/lobectomies was significantly superior in comparison with LCP after pneumonectomies (78.1% vs.63.7%, P=0.00001 by log-rank test). AT significantly improved 5YS (66.3% vs. 34.8%) (P=0.00000 by log-rank test) only for LCP with N1-2. Cox modeling displayed that 5YS of LCP significantly depended on: phase transition (PT) early-invasive LC in terms of synergetics, PT N0—N12, cell ratio factors (ratio between cancer cells- CC and blood cells subpopulations), G1-3, histology, glucose, AT, blood cell circuit, prothrombin index, heparin tolerance, recalcification time (P=0.000-0.038). Neural networks, genetic algorithm selection and bootstrap simulation revealed relationships between 5YS and PT early-invasive LC (rank=1), PT N0—N12 (rank=2), thrombocytes/CC (3), erythrocytes/CC (4), eosinophils/CC (5), healthy cells/CC (6), lymphocytes/CC (7), segmented neutrophils/CC (8), stick neutrophils/CC (9), monocytes/CC (10); leucocytes/CC (11). Correct prediction of 5YS was 100% by neural networks computing (area under ROC curve=1.0; error=0.0).
CONCLUSIONS: 5YS of LCP after radical procedures significantly depended on: 1) PT early-invasive cancer; 2) PT N0--N12; 3) cell ratio factors; 4) blood cell circuit; 5) biochemical factors; 6) hemostasis system; 7) AT; 8) LC characteristics; 9) LC cell dynamics; 10) surgery type: lobectomy/pneumonectomy; 11) anthropometric data. Optimal diagnosis and treatment strategies for LC are: 1) screening and early detection of LC; 2) availability of experienced thoracic surgeons because of complexity of radical procedures; 3) aggressive en block surgery and adequate lymph node dissection for completeness; 4) precise prediction; 5) adjuvant chemoimmunoradiotherapy for LCP with unfavorable prognosis.
Prix Galien International 2024 Forum ProgramLevi Shapiro
June 20, 2024, Prix Galien International and Jerusalem Ethics Forum in ROME. Detailed agenda including panels:
- ADVANCES IN CARDIOLOGY: A NEW PARADIGM IS COMING
- WOMEN’S HEALTH: FERTILITY PRESERVATION
- WHAT’S NEW IN THE TREATMENT OF INFECTIOUS,
ONCOLOGICAL AND INFLAMMATORY SKIN DISEASES?
- ARTIFICIAL INTELLIGENCE AND ETHICS
- GENE THERAPY
- BEYOND BORDERS: GLOBAL INITIATIVES FOR DEMOCRATIZING LIFE SCIENCE TECHNOLOGIES AND PROMOTING ACCESS TO HEALTHCARE
- ETHICAL CHALLENGES IN LIFE SCIENCES
- Prix Galien International Awards Ceremony
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
Anti ulcer drugs and their Advance pharmacology ||
Anti-ulcer drugs are medications used to prevent and treat ulcers in the stomach and upper part of the small intestine (duodenal ulcers). These ulcers are often caused by an imbalance between stomach acid and the mucosal lining, which protects the stomach lining.
||Scope: Overview of various classes of anti-ulcer drugs, their mechanisms of action, indications, side effects, and clinical considerations.
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.
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Epidemiology and cycle of microbial diseases
1. Epidemiology and cycle of
Microbial Diseases
Dr. Chhaya Sawant
Shri C. B. Patel Research centre, Mumbai, India
2. Epidemiology means?
The science that evaluates patterns of disease
occurrence, frequency, determinants,
distribution, and control of health and disease in
a defined human population.
Epidemiology leads to the identification of causal
and preventive factors in human disease.
3. Epidemiology Defined
• ―The study of epidemics‖
• Greek roots
epi = upon (as in ―epidermis‖)
demos = the people (as in demography)
ology = ―to speak of‖, ―to study‖
• Modern definitions of epidemiology refer to
– distributions in populations (statistical)
– determinants
(pathophysiology, biology, chemistry, psychology)
– control of health problems
(biological, social, economic, political, administrativ
e, legal)
4. Epidemiology
• Also referred to as “Medical Ecology”. Why?
- Study of a disease in its natural environment.
Study of the clinical aspects and ecological
aspects of a given disease are important for the
public health measures to control the diseases
to be effective
5. Epidemiology
• Also referred to as “Medical Ecology”. Why?
- Study of a disease in its natural environment.
Study of the clinical aspects and ecological
aspects of a given disease are important for the
public health measures to control the diseases
to be effective
6. The Black Plague
• 1330’s, outbreak of plague in China.
• Spread to Italy and the rest of Europe.
• 25 million people died in just under five
years between 1347 and 1352 – 1/3 of the
population of Europe.
Influenza – 1918
Killed 50 to 100 million people worldwide, in
a single year.
7. The First Indications of Person-to-Person
Spread of an Infectious Disease
Edward Jenner (1749-1823) - developed a vaccine against smallpox using cow pox (160 years
before virus was identified)
In 1773 Charles White, an English surgeon and obstetrician, published his ―Treatise on the
Management of Pregnant and Lying-In Women‖ with Puerperal fever.
Puerperal fever is an acute febrile condition that can follow childbirth and is caused by
streptococcal infection of the uterus and/or adjacent regions.
In 1795 Alexander Gordon, a Scottish obstetrician, published his ―Treatise on the
Epidemic Puerperal Fever of Aberdeen‖ which demonstrated for the first time the
contagiousness of the disease.
In 1843 Oliver Wendell Holmes, a noted physician and anatomist in the United States, published a
paper entitled ―On the Contagiousness of Puerperal Fever‖.
Hungarian physician Ignaz Phillip Semmelweis (1847 and 1849 ), the first person to realize that a
pathogen could be transmitted from one person to another.
The pioneer of antisepsis in obstetrics – Saviors of Mothers. 32 years before causal agent was
discovered
John Snow (1813-1858) described the association between dirty water and cholera (44 years before
vibrio was identified
8. Brief History of Epidemiology
Classical Nutritional Epidemiology
–James Lind (1716-1794)
• conducted an experiment which showed that scurvy could
be treated and prevented with limes, lemons, and oranges
– ascorbic acid was discovered 175 years later
–Joseph Goldberger (1874-1927)
• identified that pellagra was not infectious but nutritional in
origin and could be prevented by increasing the amount of
animal products in the diet and substituting oatmeal for corn
grits
– niacin was discovered 10 years later
9. Objectives of Epidemiology in Emergencies
To identify the priority health problems in the affected
community
To determine the extent of disease existing within a
community
To identify the causes of disease and possible risk
factors
To determine the priority health interventions
To determine the extent of damage and capacity of
local infrastructure
To monitor health trends of the community
To evaluate the impact of health programs
10. Role of an Epidemiologist
• Traces the spread of a disease in a population
- To identify its origin
- Mode of Transmission
• With the help of Data Obtained from
- Clinical studies
- Disease reporting surveys
- Insurance questionnaires
- interviews with patients
This will help him define common factors that
constitute a disease.
11. Important Terms
• Attack rate : The proportional number of cases developing in the population that was
exposed to the infectious agent
• Communicable disease : An infectious disease that can be transmitted from one host
to another
• Non-communicable disease : A disease that is not transmitted from one host to
another
• Herd immunity : A phenomenon that occurs when a critical concentration of immune
hosts prevents the spread of an infectious agent
• Incidence : The number of new cases of a disease in a population at risk during a
specified period of time
• Index case : The first identified case of a disease in an outbreak or epidemic
• Outbreak : A cluster of cases occurring during a brief time interval and affecting a
specific population; an outbreak may herald the onset of an epidemic
• Portal of entry : Surface or orifice through which a disease-causing agent enters the
body
• Portal of exit : Surface or orifice from which a disease-causing agent exits and
disseminates
• Prevalence : The total number of cases in a given population at risk at any point in
time
• Reservoir : The natural habitat of a disease-causing organism
12. Infectious disease: the unique factor
Historical approach :
Infectious diseases can be spread from human to human
(or animal to human)
Modern Approach :
Alcohol and drug abuse, cancer, mental conditions, acts of
violence and exposure to lead paint.
13. Cycle of Microbial Disease
Person to person
Reservoir transmission
Portal of exit Susceptible Host
Portal of entry
Agent
Mode of transmission
14. Chain of transmission
Reservoir
Human
Person with symptomatic illness
Carriers:
Asymptomatic
Incubating
Convalescent
Chronic
Animal: zoonosis
Environmental: soil, plant, water
16. Chain of transmission
Mode of Transmission
Direct
Direct contact
Secretions,
Blood,
Faeces/urine
Droplet spread
Indirect
Food/water
Aerosol
Animal vectors
Fomites
Medical devices
and treatments
17. Transmission
• Transmission of a disease from its reservoir to the
next susceptible host.
• Through contact, ingestion of food or water, or via a
living agent such as an insect is called horizontal
transmission.
• Vertical transmission, the transfer of a pathogen
from a pregnant woman to the fetus, or from a mother
to her infant during childbirth.
e.g. Congenital syphilis, Group B streptococci, can
infect the newborn as it passes through the birth canal
19. Frequency and distribution based
Classification
• Sporadic level: occasional cases occurring at irregular
intervals
• Endemic level: persistent occurrence with a low to moderate
level
• Hyper Endemic level: persistently high level of occurrence
• Epidemic : occurrence clearly in excess of the expected level
for a given time period
• Pandemic: epidemic spread over several countries or
continents, affecting a large number of people
20. A Graph Illustrating Three Epidemics
The solid blue line indicates the expected number of endemic cases.
The connected red dots indicate the actual number of cases.
Epidemics (marked by brackets) are sharp increases in the number of cases of a
disease above that which is normally expected (solid line).
21. Disease Progression
• Infection
• Incubation period
• Prodromal stage
• Period of illness
• Convalescence
22. Factors that Influence the Epidemiology
of Disease
• The Dose
• The Incubation Period
• Population Characteristics
- Immunity to the pathogen.
- General health.
- Age.
- Gender
- Religious and cultural practices.
- Genetic background.
23. Measuring Frequency
• Three important statistical measures of disease
frequency
– morbidity rate
– prevalence rate
– mortality rate
24. Morbidity rate :
Measures the number of individuals that become ill due to a
specific disease within a susceptible population during a
specific time interval.
Morbidity rate =
Number of new cases during a specific time
Total number of individuals in population
• E.g. 700 new cases of influenza per 100,000 individuals is
0.7%.
Prevalence Rate
The total number of individuals infected in a population at
any one time no matter when the disease began
25. • Mortality rate
Number of deaths from a disease per number of cases of the
disease
• Mortality rate =
Number of deaths due to given disease
size of total population with disease
If 500 people in a town of 100,000 become infected with HIV and 100
die, the mortality rate is…
26. Recognition of an Infectious Disease in a Population
1. Generation of morbidity data from case reports
2. Collection of mortality data from death certificates
3. Investigation of actual cases
4. Collection of data from reported epidemics
5. Field investigation of epidemics
6. Review of laboratory results: surveys of a population for antibodies against
the agent and specific microbial serotypes, skin tests, cultures, stool
analyses, etc.
7. Population surveys using valid statistical sampling to determine who has the
disease
8. Use of animal and vector disease data
9. Collection of information on the use of specific biologics—
antibiotics, antitoxins, vaccines, and other prophylactic measures
10. Use of demographic data on population characteristics such as human
movements during a specific time of the year
11. Use of remote sensing and geographic information systems
27. • Recognition of an Epidemic
• Two types of epidemics
– common source epidemic
– propagated epidemic
• Common source epidemic
• Reaches a peak within a short period of time -1 to 2 weeks)
• A moderately rapid decline in the number of infected patients
• A single common contaminated source - food (food poisoning)
or water (Legionnaires’ disease).
• Propagated epidemic (Host to Host)
• A relatively slow and prolonged rise and then a gradual decline
in the number of individuals infected.
• A single infected individual into a susceptible population.
• E.g. Increase in mumps or chickenpox cases, Spread of HIV
infection.
28. Seasonal Cycles of diseases
• The season of the year in which the epidemic
occurs may also be significant.
• Respiratory diseases including Influenza, Respiratory Syncytial
Virus infections, and the common cold are more easily
transmitted in crowded indoor conditions during the winter.
• Conversely, vector- and food-borne diseases are more often
transmitted in warm weather when people are more likely to be
exposed to mosquitoes and ticks, or eating picnic food that has
not been stored properly.
29. Seasonal Cycles of diseases
Seasonal Occurrence of Seasonal Occurrence of
Respiratory Infections Caused by Gastrointestinal Diseases
Respiratory Syncytial Virus
30. Herd Immunity.
Resistance of a population to
infection and to spread of an
infectious organism because of
the immunity of a large
percentage of the population
The kinetics of the spread of an
infectious disease and the effect
of increasing the number of
immune individuals in the
population in limiting the disease.
On day 1, a single infected
individual enters the population.
The incubation period is 1 day,
and recovery occurs in 2 days.
The number of susceptible
individuals is the total population
on day 1.
31. Diagrammatic representation of the spread of an imaginary propagated epidemic.
The lower curve represents the number of cases and the upper curve the number of
susceptible individuals. Notice the coincidence of the peak of the epidemic wave
with the threshold density of susceptible individuals.
32. The number of infected and recovered are illustrated in the two graphs.
33. Herd immunity
• Resistance of a population to infection and to spread
of an infectious organism because of the immunity of a
large percentage of the population
• Level can be altered by introduction of new
susceptible individuals into population
• Level can be altered by changes in pathogen
– antigenic shift – major change in antigenic character of
pathogen (recombination in birds, pigs totally new antigen
types)
– antigenic drift – smaller antigenic changes (point-mutational
changes)
34. Virulence and the Mode of Transmission
Evidence suggests correlation between mode
of transmission and degree of virulence
– direct contact less virulent
– vector-borne highly virulent in human host;
relatively benign in vector
– greater ability to survive outside host more
virulent
35. The host community:
• Infection --- immunity --- coexistence
• Host-pathogen
• co evolution: the case of the rabbit-myxoma virus
– Transmitted by mosquitoes
– Rabbit mortality:
susceptibility of new born rabbits to a moderately virulent strain of
the virus
• – Virus virulence: infection of lab rabbits with wild virus
1950 - 1980: Pre introduction levels of rabbit
infestation Introduction of a second virus
(RHDV; host-to-host transmission; instant
killing) --- co evolution.
36. Emerging and Reemerging Infectious
Diseases and Pathogens
By the 1990s, the idea that infectious diseases
no longer posed a serious threat to human
health was obsolete.
It is now clear that globally, humans will
continually be faced with both new infectious
diseases and the reemergence of older
diseases once thought to be conquered
(e.g., tuberculosis, dengue hemorrhagic
fever, yellow fever)
37. Emerging and Reemerging Infectious
Diseases and Pathogens
Infectious Disease Mortality in the United States Decreased Greatly during Most of
the Twentieth Century.
The insert is an enlargement of the right-hand portion of the graph and shows that the
death rate from infectious diseases increased between 1980 and 1994.
38. Systematic epidemiology
The increased importance of emerging and
reemerging infectious diseases has stimulated the
establishment of a field called
systematic epidemiology
Which focuses on the ecological and social factors that
influence the development of these diseases.
39. Factors characteristic of the modern world favoring the
development and spread of these microorganisms and their
diseases
1. Unprecedented worldwide population growth, population shifts
(demographics), and urbanization
2. Increased international travel
3. Increased worldwide transport (commerce), migration, and relocation of
animals and food products
4. Changes in food processing, handling, and agricultural practices
5. Changes in human behavior, technology, and industry
6. Human encroachment on wilderness habitats that are reservoirs for insects
and animals that harbor infectious agents
7. Microbial evolution (e.g., selection pressure) and the development of
resistance to antibiotics and other antimicrobial drugs (e.g., penicillin-
resistant Streptococcus pneumoniae, methicillin-resistant Staphylococcus
aureus, and vancomycin-resistant enterococci)
40. Factors characteristic of the modern world favoring the
development and spread of these microorganisms and their
diseases
8. Changes in ecology and climate
9. Modern medicine (e.g., immunosuppression)
10. Inadequacy of public infrastructure and vaccination programs
11. Social unrest and civil wars
12. The possibility of bioterrorism
13. Virulence-enhancing mechanisms of pathogens (e.g., the mobile
genetic elements—bacteriophages, plasmids, transposons)
41. Some Examples of Emerging and Reemerging Infectious Diseases.
Although diseases such as HIV are indicated in only one or two significant locations,
they are very widespread and a threat in many regions.
42. Public Health System
The public health system comprises of a
network of clinical microbiologists, nurses,
physicians, epidemiologists, and infection control
personnel who supply epidemiological
information to a network of local, state, national,
and international organizations.
43. The Role of the Public Health System
• Control of Epidemics (Three Types)
• First Type : Directed toward reducing or
eliminating the source or reservoir of infection
1. Quarantine and isolation of cases and/or carriers
2. Destruction of an animal reservoir of infection
3. Treatment of sewage to reduce water contamination
4. Therapy that reduces or eliminates infectivity of the
individual
44. Control of Epidemics (Three Types)
• The second type : designed to break the
connection between the source of the infection
and susceptible individuals. (general sanitation
measures - Transmission)
1. Chlorination of water supplies
2. Pasteurization of milk
3. Supervision and inspection of food and food handlers
4. Destruction of vectors by spraying with insecticides
45. Control of Epidemics (Three Types)
• The Third type : reduces the number of
susceptible individuals and raises the general
level of herd immunity by immunization.
1. Passive immunization to give a temporary
immunity following exposure to a pathogen or when
a disease threatens to take an epidemic form
2. Active immunization to protect the individual from the
pathogen and the host population from the epidemic
The most important is Surveillance – Observation,
recognition and reporting of Diseases as they occur.
46. Precautions to be taken by individuals to prevent
travel-related infectious diseases.
1. If one is traveling to an area where malaria is
endemic, weekly prophylaxis before entering the area and
after leaving the area is recommended.
2. Travelers should recall the benefits of abstinence or protective
sexual practices, especially the use of condoms. Hepatitis B
vaccine should be administered if it is indicated.
3. Travelers should avoid uncooked food, non bottled water and
beverages, and unpasteurized dairy products. Use bottled
water for drinking, making ice cubes, and brushing teeth.
4. Wash hands with soap and water frequently, especially before
each meal.
47. Precautions to be taken by individuals to prevent
travel-related infectious diseases.
5. To prevent respiratory infections, avoid excessive outdoor
activities in areas of heavy air pollution during hot or humid
parts of the day. Consider tuberculin skin testing before and
after travel.
6. Minimize skin exposure and use repellents to prevent
arthropod-borne illnesses (e.g., malaria, dengue, yellow fever,
Japanese encephalitis).
7. Avoid skin-perforating procedures (e.g., acupuncture, body
piercing, tattooing, venipuncture, sharing of razors).
8. Do not pet or feed animals, especially dogs and monkeys.
9. Avoid swimming or wading in non-chlorinated freshwater.
48. Nosocomial Infections
• Nosocomial diseases - caused by bacteria, most of which are
noninvasive and part of the normal microbiota;
• Viruses, protozoa, and fungi are rarely involved.
• Source of Hospital Infection
• Endogenous sources - Patient’s own microbiota.
• Exogenous sources are other than the patient’s own microbiota
.
• In either case the pathogen colonizing the patient may
subsequently cause a nosocomial disease.
49.
50. The Hospital Epidemiologist
• The services provided by the hospital epidemiologist
should include
1. Research in infection control
2. Evaluation of disinfectants, rapid test systems, and other products
3. Efforts to encourage appropriate legislation related to infection control,
particularly at the state level
4. Efforts to contain hospital operating costs, especially those related to fixed
expenses such as the DRGs (diagnosis related groups)
5. Surveillance and comparison of endemic and epidemic infection frequencies
6. Direct participation in a variety of hospital activities relating to infection
control and maintenance of employee health
7. Education of hospital personnel in communicable disease control and
disinfection and sterilization procedures
8. Establishment and maintenance of a system for identifying, reporting,
investigating, and controlling infections and communicable diseases of
patients and hospital personnel
9. Maintenance of a log of incidents related to infections and communicable
diseases
10. Monitoring trends in the antimicrobial drug resistance of infectious agents
51. The Emerging Threat of Bioterrorism
• The Centers for Disease Control and
Prevention recently defined bioterrorism as
―The intentional or threatened use of viruses, bacteria,
fungi, or toxins from living organisms to produce death
or disease in humans, animals, and plants.‖
• a few kilograms of anthrax can kill as many people as
a Hiroshima-size nuclear bomb
The goal of bioterrorism is to produce fear in
the population with subsequent disruption of
society
52. History of Bioterrorism
• Biological warfare (BW) employed as far back as 6th century
BC.
• Examples of past BW:
14th Century: Mongols catapulted corpses with bubonic plague over walls
into Crimea.
15th Century: Pizarro presented native South Americans with smallpox-
contaminated clothing.
1940: Japan’s ―Unit 731‖ dropped plague-infected fleas over Manchuria &
China.
1984 : Rajneeshee Cult contaminated restaurant salad bars with Salmonella
typhimurium.
1995: Aum Shinrikyo cult attempted unsuccessfully to disperse BW agents
in aerosol form; sarin gas attack in Tokyo.
2001: Anthrax-contaminated letters to U.S. media and government offices.
53. • In 1998, the U.S. government launched the first
national effort to create a biological weapons defense.
The initiatives include
• The first ever procurement of specialized vaccines and
medicines for a national civilian protection stockpile;
• investment of more time and money in genome sequencing,
new vaccine research, and new therapeutic research;
• development of improved detection and diagnostic systems;
• preparation of clinical microbiologists and the clinical
microbiology laboratory as members of the ―first responder‖
team, which is to respond in a timely manner to acts of
bioterrorism.
54. Preventions: International
treaties, strategic
preparedness (vaccines), make this
world a better place for everyone
• Awareness
• Laboratory Preparedness
• Plan in place
• Individual & collective protection
• Detection & characterization
• Emergency response
• Measures to Protect the Public’s
Health and Safety
• Treatment
• Safe practices
55. Future Challenges to Public Health
• Emergence of new infectious diseases and re-emergence of
old ones.
• Inequities in health care.
• Threat of large scale terrorist attacks using nuclear, biological
and chemical agents.
• Chronic diseases – coronary heart disease, obesity, diabetes,
cancer.
• Continued political instability.
• International coordination of public health efforts.
• Ethics.
• Ignorance.
56. Types of Epidemiological Studies Undertaken
• Descriptive Studies – The Person, The Place, The Time,
• Analytical Studies
- Cross-Sectional Studies : A cross-sectional study surveys a range of
people to determine the prevalence of any of a number of characteristics
including disease, risk factors associated with disease, or previous exposure
to a disease-causing agent.
- Retrospective Studies : A retrospective study is done following a
disease outbreak. This type of study compares the actions and events
surrounding clinical cases (individuals who developed the disease) against
appropriate controls (those who remained healthy).
- Prospective Studies : A prospective study is one that looks ahead to
see if the risk factors identified by the retrospective study predict a tendency
to develop the disease. Cohort groups, which are study groups that have a
known exposure to the risk factor, are selected and then followed over time.
• Experimental Studies
57. Investigation of a GI illness
outbreak
http://www.cdc.gov/eis/casestudies/xoswego.401-303.student.pdf
58. Investigation of a GI illness outbreak
http://www.cdc.gov/eis/casestudies/xoswego.401-303.student.pdf
59. Investigation of a GI illness outbreak
If you were to administer a questionnaire to the church
supper participants, what information would you collect?
1. What did you eat?
2. How much did you eat?
3. How long after you ate did you begin to feel sick?
4. How long did it last?
5. Did anyone at the supper show illness prior to the supper?
6. What did you drink?
7. How was the food prepared/ stored?
http://www.cdc.gov/eis/casestudies/xoswego.401-303.student.pdf
61. Investigation of a GI illness outbreak
http://www.cdc.gov/eis/casestudies/xoswego.401-303.student.pdf
62. Investigation of a GI illness outbreak
Without having clinical isolates from the infected
individuals for examination, how might you tentatively
identify the causative agent?
1. Temperature of storage vs organism?
2. Food vs organism?
3. Homemade vs commercial?
4. Symptoms
5. Culture ice cream.
It the outbreak has already ended, what is the value of
working up the case?