Cdc ppt for bsc nursing unit 1 11
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Transcript of Cdc ppt for bsc nursing unit 1 11
CDC FOR BSC NURSING
BY GUGS A NEMERA
1BY GN 2013
Learning objective At the end of the session students will be able to:• clearly differentiate between CD and NCD• Define at least five terms those commonly used in CD
and relate it to practical situations • Discuss CD
2BY GN 2013
UNIT ONE INTRODUCTION
Disease can be communicable or non communicableCommunicable disease in turn classified into several divisions based on
causative organismsclinical presentation or system of body affected
This classification is valuable for Clinician MicrobiologistsEpidemiologists Parasitologsts .
3BY GN 2013
INTRODUCTION CONT’DCommunicable continues to remain a leading cause of morbidity, disability and mortality worldwide. It accounts for one tenth of deaths in rich countries and six out of ten deaths in poorer countries .for instance annually worldwide
2 m deaths occurs from diarrhea4 m die of LRTI700,000 die from measles 2 m die from TB90% from developing countries
4BY GN 2013
Definition of common terms (important terms)
Carrier- A person that carries a specific infectious
agent and can transmit to others but has no clinical
sign of infection.
Case - A person identified as having specific health
problem or disease of interest
Case definition- standard criteria for deciding whether
a person has particular disease or health problem.
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Chain of disease transmission: is a logical sequence of
factors or links of a chains that are essential for
development of the infectious agent and progression
of disease
Chemoprophylaxis- Administration of drug to prevent
the development or progression of an infection to
actual disease
Mass chemoprophylaxis
Selective chemoprophylaxis 6
Definition of common terms cont’d
BY GN 2013
Chemotherapy: Use of chemicals to treat a clinically manifest disease
Assignment Write at least 250 chemotherapeutic agent those
commonly used in Ethiopia
S.No Drug Dose Route Frequency Duration Indication 1
2
250
Definition of common terms cont’d
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Communicable period: the time during which an
infectious agent may be transferred directly or
indirectly from infected person to susceptible host
Contact - A person or animal that has had an
opportunity to acquire the infection following
association with infected person, animal or
contaminated environment
8
Definition of common terms cont’d
BY GN 2013
Control /Containment – Operation aimed at reducing the prevalence of the disease to a level where it is not a major public health important.
Disinfection: the killing of infectious agents outside the body by direct exposure to physical or chemical agents.
Sterilization – distraction of all forms of life by heat, irradiation, gas or chemical treatment.
Definition of common terms cont’d
9BY GN 2013
Contamination :The presence of an infectious agent on
the body surface or other inanimate articles or
substances
Note: contamination on body surface does not imply
carrier state
Drug resistance – The ability of infectious agent to
survive despite the administration of antimicrobial in a
dose equal to or higher than the usual recommended
dose10
Definition of common terms cont’d
BY GN 2013
Disinfection- the killing of infectious agents outside the body
by direct exposure to physical or chemical agents.
Concurrent disinfection→ application of disinfective
measure as soon as possible of the discharge of infectious
material from the body of an infected person or after the
soiling of material with such infectious discharge.
Terminal disinfection → is the application of disinfective
measures after the pt. has been removed by death or to
hospital, isolation or other partice has been discontinued11
Definition of common terms cont’d
BY GN 2013
Sterilization – distraction of all forms of life by heat,
irradiation, gas or chemical treatment.
Disinfestations – The procedure of destroying or
removing undesired small forms of animals particularly
arthropods, rodents, present up on the person,
clothing or in the environments of an individual or
domestic animal using chemicals or physical agents.
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Definition of common terms cont’d
BY GN 2013
Elimination – eradication of disease from large geographical region or political jurisdiction.
Endemic – Continuous presence (usual prevalence) of a disease or infectious agent with in a geographical area.
Epidemic or outbreak- occurrence of cases of an illness with the frequency that is clearly in excess of what is expected in a given region therefore demanding emergency control.
Definition of common terms cont’d
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Epidemic Thresh hold- The minimum number of
cases indicating the beginning of an out breaks.
Eradication-Termination of all transmission of
infection through surveillance and control.
Host- A person or other living animal that
accommodates infectious agent under normal
conditions.
Definition of common terms cont’d
14BY GN 2013
Immune individual – A person or animal that has
specific protective antibody and/or cellular immunity
as a result of pervious exposure /infection,
immunization.
Immunity – resistance usually associated with the
presence of antibodies
Immunogenicity: -The ability of an agent to produce
specific immunity.15
Definition of common terms cont’d
BY GN 2013
Exposure – meeting with an infectious agent in the way
that may cause disease.
Illness: -Individual or subjective feeling of discomfort.
Disease: -A state of physiological and psychological
dysfunction.
Incubation period – The time interval from the time of
infection to the time of appearance of clinical
manifestation
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Definition of common terms cont’d
BY GN 2013
Infection – The entry and development of an infectious
agent in the body of humans or animals.
Nosocomial infection → An infection occurring in
patient in hospital and other health facility in whom the
infection was not present or incubating at time of
admission or residual of infection during previous
admission.
Community acquired infection – infection that occurs in
the community (general population.)
Definition of common terms cont’d
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Infectious agent – Bacteria, viruses, Fungi or parasites or
their products that can cause disease.
Infectious individual: A person or an animal from which the
infectious agent can be naturally acquired.
Infestation- The lodgement, development and reproduction
of arthropods on the surface of the body or in the clothing.
This also used for invasion of the gut by parasitic worms.
Inoculums size – The minimum size of infectious agent or its
products that can cause disease.
18
Definition of common terms cont’d
BY GN 2013
Isolation – Keeping infected persons or animals in
separate place for as long as they can transmit
diseaseStrict isolation Contact isolationRespiratory isolation TB. Isolation. Enteric precaution Drainage /secretion precautions-
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Definition of common terms cont’d
BY GN 2013
Primary or index case- A person who acquires a disease
through exposure and brings it in to population
Notifiable disease – disease for which regular, frequent
and timely information on individual cases is considered
necessary for prevention and control of disease.
Notification – The processes by which cases or out
breaks one brought to the knowledge of the health
authorities.
20
Definition of common terms cont’d
BY GN 2013
Quarantine- Restriction of the activity of well person or animal who have exposed to a case of communicable disease during its periods of communicability.
Definition of common terms cont’d
21BY GN 2013
Mode of Transmission- any mechanism by
which infectious agent spread from source or
reservoir to a person.
Pollution – The presence of offensive, but not
necessarily infectious matter in the
environment
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Definition of common terms cont’d
BY GN 2013
Reservoir- Any person, animal, arthropod, plant, soil
etc in which the infectious agent normally lives and
reproduce itself in such a manner that it can be
transmitted to a susceptible host.
Secondary case – A person infected by primary case.
Surveillance- Systematic collection, collation and
analysis of data, dissemination information for
action.
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Definition of common terms cont’d
BY GN 2013
Susceptible host- person or animal not possessing sufficient
resistance against particular infectious agent to prevent
contracting infectious disease when exposed to it.
Transmission: any mechanism by which infectious agent
spread from source or reservoir to a person.
Direct transmission – immediate transfer of infectious agent to a
suitable portal of entry (direct contact, projection)
Indirect transmission- transfer of infectious agent through
intermediate means (vehicle born, contaminated materials vector
born)
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Definition of common terms cont’d
BY GN 2013
Transmission cycle -is a cycle which describes
how an organism grows, multiplies and
spreads. In some cases man may be the only
host in which case the infection spreads
directly from man to man. E.g. measles. In
some cases like malaria the transmission cycle
involves man and mosquito
25
Definition of common terms cont’d
BY GN 2013
Absolute or complete quarantine, the limitation of freedom of movement of those exposed to a communicable disease for a period of time not longer than the longest incubation period of that disease in such manner as to prevent effectual contact with those not so exposed.
26
Definition of common terms cont’d
BY GN 2013
Modified quarantine: A selective partial
limitation of freedom of movement of
contacts commonly on the bases of known or
presumed differences in susceptibility and
related to the longer of disease transmission
27
Definition of common terms cont’d
BY GN 2013
Universal precaution – Simple standard procedure to be used
during care of patients at times to minimize the risk of
transmission.
Virulence – The ability of infectious agent to invade and damage
the tissue of the host and cause death.
Zoonoses – An infectious disease that is transmissible under
normal condition from animal to human.
Zonosis – An infection or infectious disease that is transmissible
under normal condition from vertebrate to human.
Definition of common terms cont’d
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Sporadic - A disease that occur in a
population in occasional and irregular
intervals.
Pandemic – worldwide epidemic disease.
29
Definition of common terms cont’d
BY GN 2013
COMMUNICABLE DISEASE/ (infectious disease)
Definitions
A disease due to specific agent or its toxic products
that a rises through transmission of that agent or its
products from infected person, animal or reservoir to
susceptible host either directly or indirectly through an
intermediate plant or animal host, vector or
intermediate environment
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Specific feature of communicable disease
A case may be risk factor
Each infectious disease has its own incubation period
People may be immune
An individual may be a source without being recognized as a
case.
There is some times a need for urgency
Preventive measures (usually) have a good scientific ground
Intervention in infectious disease can have several effects 31BY GN 2013
Classification of communicable disease
It may be classified in several ways i.e. byClinical manifestation Time course Taxonomy of infectious agent Mode of transmission
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Based on C/m or system involved
Diarrhoeal diseaseFebrile illnessRespiratory tract infection Central Nervous system infectionCardiovascular system infection UTICutaneous
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Based on time course
Acute Disease with short durationneeds urgent careRapidly progressive Abrupt on set.
Chronic Indicate duration usually
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Based on taxonomy of infectious agent
Metazoan ProtozoalBacterial Fungal Viral
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Based on mode of transmission ¨ Airborne diseases (respiratory tract as portal of entry and/or exit)
¨ Feco-oral transmitted diseases (GIT as entry and/or exit)
¨ Direct contact (Mucus membranes and/or skin as portal of entry /exit)¨ Direct inoculation¨ Vector bone disease ¨ Inoculation by bite of animal/ contacts with
animal products ( zoonosis ).
36BY GN 2013
Unit two:Chain of disease transmission (diseases
transmission dynamics)
37BY GN 2013
Learning objectiveAt the end of the session students will be able to:
1.Describe Chain of disease transmission2.List major effects of agent on the host
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Chain of disease transmission DefinitionsA logical order of events which must occur in
order for disease causing organisms to cause infection.
Series that is essential to the development of the infectious agents and propagation of disease.
There are six successive events implicated in the chain of disease transmission
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Chain of disease transmission cont’d
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1.Infectious Agent
• It can be an organism or its toxin• Infection agents’ needs
MultiplicationSurvival
ReservoirsPersistence Latency Vector Intermediate host
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Multiplication→ two methods – Asexual (almost exact replicas produced →any
natural selection occur on the batches than single individual.
– Sexual- scope of variety are there
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Survival Agent survive by finding suitable hosts Agent prolong the period of survival by different methods ReservoirsSuitable place to store infectious agent Reservoir can be humans, animals, vectors or inanimate
environment (soil, waters)Persistence –Development of special stages by agent to with stand
distraction in adverse environment. E.g. forming cyst (protozoa), eggs (nematodes) spore (bacteria)
•
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Latency –Developmental stage in the environment not
Infective to a new host. –Parasite time of suitable condition
Vector –Parasite use service of arthropods to transmit from
one host to other – It can be part of transmission process (Mosquito)
Intermediate host – some parasite needs intermediate host for
development before they invade the final host.E.g. Schistosoma uses a molluscan
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Effect of the agent on host
If enough agents survive to infect a new host, they will produce a reaction or illness.
The effect of host is determined by VirulenceToxicity Dose response
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2.Reservoir of infection
A living or non living in which an infectious agent normally lives, transforms and multiplies on which it primarily for survival and where it produce itself in such a way that it can be transmitted to new susceptible host.
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Types of reservoir A. Man as the only reservoir
MeaslesGonorrhoeaSyphilisSmall poxTyphoid Meningococcal meningitis
Transmission cycle man to man
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Types of reservoir cont’d
B. Animals as reservoir Infectious disease where animals are primary
reservoirs includes: Bovine Tuberculosis – Cow to man Brucellosis – Cows, pigs and goats to man Anthrax – Cattle, sheep, goats, horse to man Rabies - Dogs, foxes, wild animal to man
Man is not essential part (usual reservoir) of the life cycle
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Types of reservoir cont’d C .Non living thing
Some of the organisms are basically saprophytes i.e. living in soil adapted to live freely in nature and biologically equipped to withstand marked environmental changes. Some of the non living reservoirs are soil, water, food etc Examples Clostridium tetani of tetanus Salmonella typhi of Typhoid fever
49BY GN 2013
3.Portal of exit
¨ Site on reservoir through which an infectious agent escapes from the reservoir.
¨ Examples GIT – Typhoid fever, Ascariasis dysentery Skin and mucus membrane-syphilis RT – TBC
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4.Made of transmission
Mechanism by which an infectious agent transferred from reservoir or infected host to new host.
Two main type of mode transmission
1. Direct transmission2. Indirect transmission
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Direct transmission
Immediate transfer of infectious agent from infected host or reservoir to an appropriate portal of entry on the susceptible host. Some of the ways of direct transmission are Direct vertical – transpalcental syphilis, HIVDirect contact – contact of if IA with skin, mucosa,
ConjunctivaDirect touching, kissing, sexual intercourseDirect projection – droplets of saliva created by
expiratory activity52BY GN 2013
Indirect Transmission
Airborne transmission Vehicle Borne transmission Vector borne transmission
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5.Route of entry
Site on susceptible host through which an infectious agent get into it
The manner of entry is one of the factors which determine whether or not the infectious agent establishes the infection
54BY GN 2013
6.Susceptible host-
A person or animal lacking of sufficient resistance to particular pathogenic agent to prevent the disease if or when exposed. In order for transmission to be completed, the existence of susceptible host is necessary
55BY GN 2013
Level of susceptibility of depends on;
Nutritional status Stress Environment Pre-existing medical condition Immune status Age
56BY GN 2013
Unit three Determinants of disease and defence
mechanism of hosts
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Learning objective
• At the end of the session the learner will be able to:
1.Describe major determinants of health using epidemiological triad
2.Discuss the defense mechanism of the host
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4.1: determinants of diseaseThe determinants of disease presented by
simply by Epidemiologic triad of host, agent and environment
Host factors DemographicBiologicalsocioeconomic
Agent factors Biological agentsPhysical agentsChemical agents Nutrient agentsMechanical agentsSocial agents
Environment:Physical environmentBiological environmentSocial environment
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4.2 Defence mechanism of the host
1. Non specific resistance or innate or natural immunity.
2. Immune system defences
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Non specific resistance or innate or natural immunity. Are immunity used for either to prevent micro
organisms from entering the body or to eliminate them rapidly
It includesA. Physical barrierB. Chemical (secreted) barrierC. Inflammatory cells or action of white blood cellsD. Inflammatory response
61BY GN 2013
Physical barrier
External barrier (skin & epithelial tissue) Internal barrier (mm) Prevent the pathogen from entering to body. Filtering and clearing the pathogen – cilia &
sneeze reflex
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Chemical (secreted) barrier
acid in stomach, enzymes in the tear and saliva ,substances in sebaceous and sweat secretion act non specifically for bacteria, fungus
interferon for virus
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Inflammatory cells or action of white blood cells
Acting as phagocyte e.g. Monocyte and macrophages.
Inflammatory responseThe major function of natural immunity
elicited in response to tissue injury or invading organism
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Immune system defences
The body has three means of defending itself when the body invaded by agents. 1st line defence 2nd line of defence 3 rd. line of defence
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1st line defenceThe phagocytic immune response involves WBC
(granulocyte and macrophage) Move to the point of attack and engulf and destroy the
invading agent 2nd line of defence
The humeral response sometimes called antibody response
A class of protein which all anti body belong is called IGAntibodies are produced by a class of lymphocyte called
B.cells3 rd. line of defence (cellular immune response)/Cell mediated
immune response Deals primary with intera-cellular pathogens It also involves lymphocyte
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Unit four
Host parasite interactions (measuring of infectiousness)
67BY GN 2013
Learning objective
• After completion of this session students will be able to
1.List common measures of infectiousness of CD
68BY GN 2013
1 Infectivity Ability of the infectious agent to invade and
multiply/produce an infection) in exposed host It can be studied/measured using The speed with which an infectious agent spreads with in a
population of close contacts /secondary attack rate SAR = (# new cases in a group – initial cases) (# of susceptible persons in group – initial cases) Sero-surveys after epidemics to determine the proportion of
persons recently infected. Measuring the progression of an infectious agent from
exposure to infection (infection rate) Infection rate (IR) = total number of infected people x 100 Total no susceptible people Host and environmental factor as well as dose route of entry,
source of infection, strain of agent influence the infectivity of an agent.
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2.Pathogenicity Ability of an agent to produce clinically manifest disease in susceptible host. Measured by the proportion of infections that result in clinically apparent disease Laboratory methods also help full Pathogenicity = total number of clinical cases x 100
Total number of sub-clinical case
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Virulence Ability of an agent to produce severs disease. Measured by proportion of clinical cases
resulting in sever clinical manifestation including squealed
Measure of virulence for human Case fatality rate (CFR) Hospitalization rate Proportion of cases disabled or who have
developed Squeal Proportion of cases that require different kinds of
treatment
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Virulence cont’d Note High infectivity different from High Pathogenicity High Pathogenicity different from High virulence e.g. Rhinovirus infection: High Pathogenicity but low virulence
Measles infection :high Pathogenicity low virulence HIV: High Pathogenicity & high virulence
72BY GN 2013
Factor determine the degree of infectivity, Pathogenicity and virulence
Strain of the agent e.g. N- Meningitides Dose of the agent e.g. Cholera Route of infection Treatment especially on virulence Season Host factor Age Nutritional status Immune response
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4.AntigencityAbility of the infectious agent to induce immune response and thus an immune state in the host.
5. ToxignocityRefers the ability of agent to produce toxin or Poison
6. Resistance Ability of the agent to resist adverse environmental condition during transmission from one host to another
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7. Disease Prevalence RateNumber of current cases per population at risk
Old: Persistent active disease contracted previously New: Onset of active disease # of EXISTING cases of a specified disease
Point prevalence Prevalence at a specific point in time
Period prevalence Prevalence over a given time interval
Usage Measure amount of illness in the community Determine health care needs of the community
75BY GN 2013
8. Disease Incidence RateNumber of new disease cases per population at
risk ¨ High incidence implies high disease occurrence ¨ Low incidence implies low disease occurrence ¨ # Of NEW cases of a disease in a period of time¨ Population at risk of developing the disease during
the same period of timeMeasured over a given time interval Usage
Determine probability of developing a specific disease Used to detect etiologic factors
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9: Immunogenicity
Infection’s ability to produce specific immunity in the host e.g. measlesMeasured by serologic surveysDepends on:Amount of antigen formed in the hostSite of multiplicationAgent’s ability to induce lifelong immunity
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Diseases According to Host-related properties
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unit five
Source of infection Learning objectives 1.Explain the three main sources of infection
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Source of infection There are three main sources of infection 1.Humans 2.Environment (inanimate, including food &
water) 3.Other animals
80BY GN 2013
A) Humans People are colonized by a wide variety of microorganisms most of which can become pathogenic given the right conditions.
Normal body flora of the healthy individual vary from one
person to another depending on age, general health,
temperature and specific local condition such as acidity in
the stomach.If normal conditions are altered, then the normal flora may be destroyed and replaced by harmful organisms .Any individual can be a source of infection although it is traditional to call exogenous infection
81BY GN 2013
B) The inanimate environment Soil, food and water can harbor organisms which act as a source of injection under the right conditions.For example, soil can contain clostridium species and if a traumatic penetrating injury carries these organisms deep into tissue anaerobic conditions may permit the organism to multiply.
82BY GN 2013
C) Other animals A variety of diseases can be spread from
animal to man and these are called zoonosis Zoonosis is an infectious disease of animals
that may be transmitted to man.Example Brucellosis, Rabies, Toxoplasmosis
83BY GN 2013
Unit six Carriers and Infected individuals
Learning objective 1.Explain the four types of carries
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Carries A person or animal that does not have apparent clinical disease but is potential source of infection to other people
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Type of carriers and its role 1.Incubatory carrier or precocious carrier (but not all
disease) Transmitting disease during incubation period i.e. from the
time of 1st shading to manifestation. E.g. Mumps ,measles
2.Convalescent carrier Transmit infection during recovery i.e. from time of recovery
to when agent stops shadingE.g. Typhoid fever ,Diphtheria
3. Asymptomatic carrier (Healthy) Transmitting a disease without ever showing clinical
manifestation High carrier rate e.g. Polio, Ameobiasis, meningo coccus
4.Chronic carrier Transmitting disease for long period/ indefinite transmission E.g. Viral Hepatitis (B, c) , Typhoid fever
86BY GN 2013
Unit sevenCourse of an infectious disease over time
Learning objective1.Discuss courses of an infectious disease over
time
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Prepatent period ¨ The time interval between infection and the point at which
infection 1st detected(lab method).¨ Between biological onset and the time of first shading of the
agent¨ Measured by the 1st shading of infectious agent by host.
2.Incubation period Time interval between infection and the 1st appearance
of clinical manifestation of disease i.e. between biological and clinical on set.
Used in investigation of disease out break
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3.Communicable period The period during which an infected host can transmit the infection to other Measured by the length of time in which the agent shades by host.Degree of transmissibility does not remain constant throughout the period of communicability as the amount of the agent that shade by infected host is variable at different point in time.
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4 Generation time Onset of infection to maximal communicability
of the host (during or after incubation period) It applies to both apparent and unapparent
infection Focuses on transmission of infection as core
concept.
90BY GN 2013
5.Latent period The time interval between recovery and the reoccurrence (as a relapse)
6.Prodormal period From onset of symptom to appearance of characteristic manifestation
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Unit eight
Spectrum of infectious disease/ gradient of infection/ Learning objective 1.Mention the possible outcome of infectious
disease
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Spectrum of infectious disease/ gradient of infection/
Spectrum means range of possible option for somethingSpectrum of infection implies the range in the expression of disease be it in terms of the degree of severity or clinical manifestation.The Sequence of event takes place in the host depending on the variety of host response.The sequence of event may be
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Spectrum of infectious disease cont’d
Five type of reaction in spectrum of disease 1. No Reaction No infection 2. Sub clinical or unapparent infection 3. Atypical disease 4. Frank disease 5. Sever disease
94BY GN 2013
Unit nineNatural history of disease
Learning objective 1.Define natural history of diseases2.Explain the four stages of natural history of
diseases
95BY GN 2013
Natural history of disease
Definition • A course of disease over time in the absence
of any intervention or unaffected by treatment.
96BY GN 2013
Natural history cont’d Characteristics Each disease has its own natural history Intervention or treatment modifies the course of
disease through time Helps to understand the intervention measures that
could be under taken in order to prevent or control diseases.
Has four stages 1. Stage of susceptibility 2. Stage of pre-symptomatic disease 3. Clinical stage 4. Stage of disability
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Natural history cont’d
Stage of susceptibility Period of exposure Disease has not yet developed but there are factors that favour occurrence (risk factors)
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Natural history cont’d
Stage of pre-symptomatic disease – sub clinical stagePeriod of latency Period biological onset Disease process has already began but no s/s are detectable Initiation of disease process can be evidenced by investigation methods (lab investigation)
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Natural history cont’d Clinical stage
Sufficient and organ change occur Sign and symptoms of disease appears Severity of a disease is variable depending on the interaction certain factor such as ¨ Nutritional status ¨ Immunity of individuals ¨ Virulence of the agent ¨ Presence or absence of medication ¨ Presence of underlying illness
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Natural history cont’d
Stage of disability or death (outcome) ¨ Disease has occurred and left over damage to
the body ¨ residual long or short duration disability ¨ chronicity ¨ death ¨ Note – Recovery can take place at any stage
101BY GN 2013
Unit ten Epidemiology and general methods of
prevention and control of communicable diseases
102BY GN 2013
Introduction to epidemiology of communicable disease
Definition: Epidemiology is the study of the frequency,
distribution and determinants of diseases and other health related events in specified populations
the application of this study to the promotion of health and to the prevention and control of health problems (Last 1983).
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Components of the definition
Population The focus of epidemiology is mainly on the population rather than individuals.
FrequencyShows epidemiology to be mainly a quantitative science It is measured by morbidity rates which quantify the occurrence of illness Mortality rates which quantity the occurrence of death
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Health related conditions conditions with directly or indirectly affect or influence health
DistributionRefers to the geographical distribution of diseases, the distribution in time, or / and distribution by type of persons affected. The part of epidemiology concerned with the frequency and distribution of diseases by time, person and place is named descriptive epidemiology.It asks the questions: - How many? Where? When? What?
105BY GN 2013
Determinants Are factors which determine whether or not a person will get a disease, or in other words, the causative factors for diseaseThe part of epidemiology dealing with the causes and determinants of diseases is analytical epidemiology It asks the questions. How? Why?
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Importance of Studying Communicable Diseases Epidemiology
Offers insights in to why disease and injury afflict some people more than others why they occur more frequently in some locations and times than in others applied science with direct and practical applicationsFor most effective ways to prevent and treat health problems. Discovery of new infectionsThe possibility that some chronic diseases have an infective origin.
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General methods of prevention and
control of communicable diseases
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Disease prevention
Inhibiting the development of a disease before it occurs or if it occurs interrupting or slowing down the progression of diseases.
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Disease control
Involves all the measures designed to reduce or prevent the incidence, prevalence and consequence of a disease to a level where it cannot be a major public health problem.
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Levels of disease prevention
The different points in the progression of a disease at which one can intervene to prevent further out come.
There are three levels of prevention.¨ Primary ¨ Secondary¨ Tertiary
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Primary prevention Preventing health people before becoming sick by altering susceptibility or reducing exposure for susceptible individuals In order to carry out effective p prevention know first who is most “at risk” of getting disease. Purpose (Objective)Promotion of healthReducing incidence of disease Prevention of exposure Prevention of disease
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Health promotion
Consists of general non specific Interventions those enhance health. Aim at individual, communities, organizations and PoliciesPromotion measures include ¨ Improve socio economic status of the population¨ Good nutrition, clothing, shelters, rest¨ A void risk behaviour ¨ Broad area of health education
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Prevention of exposureAny intervention which prevents the coming
in contact between an infectious agent and a susceptible host.
This includes actions such asProvision of safe and adequate waterproper excreta disposalvector controlsafe environment at home, at school and at work
on the streets
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Prevention of diseaseDuring the latency period between exposure
and the biological onset of the disease. An example for this is immunization.
N.B. Immunization against an infectious
organism does not prevent it from invading the immunized host but prevents it from establishing an infection.
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Prevention of disease cont’d Breast feeding is an example of intervention that
acts at all three levels of primary Prevention.Health promotion: By providing optimal nutrition for a young child, either as the sole diet up to six months of age, or as a supplement in later age.Prevention of exposure: by reducing exposure of the child to contaminated water.Prevention of disease after exposure: by the provision of ant-infective factors, including antibodies, WBCs and others
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Primary prevention cont’d
Target- total population Specific protective measures
Immunization Environmental sanitation Prevention against accidents Prevention of occupational hazards
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Secondary prevention (2preventions)Prevention after biological onset but before permanent
damage occur Include early dictation and prompt treatment of disease in
such a way that it is possible to: ¨ Cure disease (curative medicine) ¨ Slow the progression¨ Prevent complication ¨ Limit disability¨ Reverse communicability¨ Reduce prevalence.
On community-Secondary prevention for the infected individual and p for potential contacts
Target population→ patients (clinical or sub clinical)
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Tertiary prevention
Takes place after permanent damage Important aspect of therapeutic and rehabilitation medicine Aim at treatment to prevent disability and death ¨ New training and especial education to help the
patient to return to some useful work & life in community.
Target- patient: E.g. Physiotherapy
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Principles of communicable disease control
Elimination of Reservoir Immunization Environmental control Vector control Surveillance
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Elimination of Reservoir
Man as reservoir Detection and adequate treatment Isolation Quarantine
Animal as reservoir ¨ Action will be determined by usefulness of the
animal
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Immunization or vaccinations
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Introductions The new born may carries antibodies transmitted
from its mother across the placenta and from early breast feeding which protecting at very vulnerable stage in life
The effect of this antibody wears off after six weeks to six month thereby the child makes their own from natural or artificial infections (immunizations)
Immunization cont’d: Definitions of important terms
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Vaccination: Administrations of any vaccine or toxoids
Immunization: The process of inducing immunity artificially
by administering antigenic substance There are two types of immunizations;
active immunization and passive immunization
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Active immunization: Involves the stimulation of immune system to produce antibodies and cellular immune responses that protect against infections. Example use of vaccine agents
Passive immunization: the process of producing temporary protection through administration of exogenously produced anti body such as Immunoglobulin. Example breast milk
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Toxoids: Modified bacterial toxin that has been made non toxic but retain the capacity to simulate antitoxins
Immunoglobulin: an antibody containing solutions made available for passive immunizations
Antitoxin: an antibody derived from the serum of animals from stimulations with specific antigens which used to provide passive immunity
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Vaccine: a suspension of attenuated life or killed micro-organisms or antigenic portions of these agents presented to potential hosts to induce immunity and prevent disease. Vaccine can be life attenuated, killed organisms and toxoids
Life attenuated; giving actual infection which is the best of all; examples measles, polio, BCG
Killed organisms: used when live attenuated strain is impossible to produce; it should be repeated. example pertussis
EPI target disease in Ethiopia
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Before 2007 øTuberculosis øTetanus øPertussis øDiphtheria øMeasles øPoliomyelitis
After 2007«Tuberculosis «Tetanus «Pertussis «Diphtheria «Measles «Poliomyelitis«Hepatitis B «Haemophilus influenzae B
« Pneumonia «Rota virus
Antigen for immunization
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1. BCG
2. Penta-valent (DPT plus HiB&Hb)
3. Polio
4. Measles
5. Tetanus toxoids( TT)
6. PCV
7. Rota virus
Epidemiological case definitions of vaccine preventable disease
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Measles: any child with fever, red eyes, and generalized rash within three or more days and history of cough, runny nose.Pertusis: any child with history persistent cough for two or more weeks, fits, and cough followed by vomiting Neonatal tetanus: Neonate with history of normal suck and cry in 1st two days of life and onset of illness between 3-28 days of age with inability to suck breast followed by stuffiness and/or convulsions more often deathPoliomyelitis: any child less than 15 years and who have AFP or any child who clinical suspect polio
EPI delivery strategy
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Static: immunization performed as a part of routine activities of the health institution Outreach: is an immunization approach in which the staff of the health unit goes out and administers vaccine for mother and children Mobile: a team of health unit staff go out of the health institutions and provide immunization as Mopping up or house to house mainly for single dose antigens campaign: like as national immunization days
Environmental control ¨ Personal and domestic hygiene¨ Proper preparation, handling ,cooking and
storage of food ¨ Use of safe water source ¨ Proper disposal of wastes and excreta
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Vector control
¨ Adulticids¨ Repellents or detergents¨ Personal protection ¨ Larvicide’s ¨ Biological control ¨ Environmental modification ¨ Insecticides
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AdulticidsKilling of adult mosquito can be done while:
¨ Flying – using knock down spray ¨ Resting- Residual insecticides
Repellents or detergentsApplied on the body in the form of lotion or
smocks Do not kill but deter from biting Made from phyethroids but other insecticide can
be added
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Personal protection Reduce the no of mosquito biteThey are cloths that cover the arms and legs Can be combined with repellents Mosquito nets Larvicide’s Act on mosquito larva by acting on
Breathing apparatus Not effective
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Biological control Use of natural methods to bring about reduction in vector
Environmental modification Making the environment no longer suitable for existence of the vector
E.g. draining of water
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Insecticides Poisons – Paris green Fumigants
Hydrogen cyanides, methyl bromide and ethylformate used on body or clothing to destroy infestation
Knock down – Pyrethrum Residual insecticide Organo chlorines
dichlorodiphenyltrichloroethane (DDT) Benzenehexahloride (RHC) - Dieldrin kill or reduce time of contact
Organophosphate e.g. Malathion inhibits cholinesterase at nerve junction and cause paralysis
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Unit eleven Surveillance and investigation and
management of outbreaks
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Surveillance Surveillance is a continuous collection, analysis, interpretation and dissemination of health information for the purpose of monitoring health events, and using the information for prevention and control of health problems.
Key qualities (elements) of surveillance Its continuous activity Its ability to detect changes in ecology or incidence of disease. The dissemination of pertinent information for action.Although surveillance is applicable to all types of diseases, primary attention should be directed towards disease amenable to effective control
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Methods of surveillance system 1.Active surveillance
2. Passive surveillance
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Active surveillance A collection of data usually on specific disease or health related events for relatively limited period of time by regular outreach on the part of health department personnel. A system in health staff make periodic field visits to health care facilities to identify new cases or death from disease (case finding) Involves Interviewing clinicians and pts Reviewing health records Surveying villages in under developed countries
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Characteristics of Active surveillance ¨ Identify Local outbreak¨ More expensive to maintain and establish as it
require good organization, funds and resources.
¨ More accurate and complete than passive
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Passive surveillance • Surveillance in which either available data on
reportable disease are used or reporting is mandated or requested with the responsibility often failing on health care provider or district health officer.
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Characteristics of Passive surveillance ¨ Problems with under reporting or lack of
completeness ¨ May dilute small out breaks in the total
regional pupation¨ In expensive and easily implemented ¨ Allow for international comparison ¨ Data is analyzed centrally ¨ Wide coverage requiring without specific
arrangement
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Types of passive surveillance Total passive carried out through predetermined reports submitted at regular intervals Simulated passive surveillance
¨ surveillance team request reports from third parties
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Step to be followed in surveillance 1. Collection of data
Name, age, sex address, occupation, vaccination, Treatment, place of infection, source of infection, exposed susceptible e
2. Compilation and analysis of dataanalysis can be made of cases by person, place and time.
3. Formulation of recommendation for action 4. dissemination and feed back
higher authorities Person and institution involved in notification &
control program To the community.
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Out break Occurrences of more cases of disease than expected in a given area among specific group of people over particular period of time.
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Outbreak is:A public, political and economic emergency An unusual event An event requiring rapid action A failure of surveillance An opportunity /for training, Research…)
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Reason to investigate out break Control /prevention Research opportunity TrainingPublic political and legal concern
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Steps in outbreak investigation 1.Preparation for field work A. Investigation
Have appropriate scientific knowledge, supplies and equipment to carry out investigation
Discuss with someone who is knowledgably about the disease.
Review applicable literature.
B. Administration C. Consultation
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2. Establish the existence of our break 3. Varity the diagnosis 4. Establish case definition
Include clinical criteria and restriction by time place and person.
must be applied to all without bias Type
Possible – Fewer of typical clinical features Probable – Typical clinical feature without lab
investigation. Confirmed
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5. Perform descriptive epidemiology. Time- when do they become ill? Place- where do they live Person- who are the cases
5Develop hypothesis source of the agent, made of transmission etc Who is becoming ill? What is a disease What is the source and the vehicle What is the mode of transmission
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6. Test hypothesis Compare with established facts When clinical, lab environmental and/or epidemiological data undoubtedly support hypothesis
8. Refine hypothesis and do additional studies
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9. Implement control measures Control source of pathogen Interrupt transmission (vector
contrle ,personal & environmental sanitation) Modify host response :
Vaccination Prophylaxis Treatment
10. Communicate the findings
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Learning objective1.List at least four diseases under national
regulation 2. list diseases under international regulation
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Unit twelve Notification and health regulation
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Introduction to Notification and health regulationInternational health regulations Require that certain disease are notified
Purpose To warn other countries and intended travellers to the country of health risk involved For assistance
Disease under international health regulation ¨ Plaque, cholera, yellow fever, Ebola
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Disease under surveillance by WHO Louse borne typhus fever RF Paralytic poliomyelitis Malaria Influenza AIDS Small poxDiphtheria, typhoid whooping cough
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National health regulation TBCLeprosy Sleeping sickness Vaccination required for international travel yellow fever
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Integrated disease surveillance and response Functional disease surveillance system is useful for priority setting, planning mobilization and allocation of resources, production and early detection of epidemics, monitoring and evaluation of intervention programs.
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Integrated disease surveillance and response (IDSR) priority disease
1.Epidemic prone Cholera Diarrhoea with b/d (shigella) Measles Meningitis Malariaplague Viral Hemorrhagic Fevers(Ebola) Typhoid fever RF Epidemic typhus
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2. Disease selected for case based surveillance Measles Poliomyelitis Dracunculiasis (Guinea worm)Neonatal tetanus
3 .Other diseases of public health importance Diarrhoea in <5 years of age Pneumonia AIDS Onchocerciasis STITB
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