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COMMUNICABLE DISEASE
EPIDEMIOLOGY,CONTROL & PREVENTION
Mohamed M.B. Alnoor
CHP300
COMMUNICABLE DISEASE
Content
Sources & Channels of infection Host-parasite relationship Cycle of infection Outcome of infection Disease mechanism Spectrum of disease
Levels of disease occurrence Control and prevention of
disease Levels of Prevention Natural History of disease
COMMUNICABLE DISEASE
DEFINITIONS
COMMUNICABLE DISEASE :EPIDEMIOLOGY :
CONTROL :
PREVENTION :
COMMUNICABLE DISEASE
DEFINITIONS
Control:
Elimination :
Eradication: Extinction:
COMMUNICABLE DISEASE
SOURCES OF INFECTIONCASE OF DISEASE : a patient CARRIER :
. Incubatory carrier . Convalescent carrier . Chronic carrier . In-apparent carrierANIMAL RESERVOIR (ZOONOSIS)INANIMATE RESERVOIR (THE SOIL)
DEFINITIONS
COMMUNICABLE DISEASE
SOURCES OF INFECTION
DEFINITIONS
Zoonosis
Reservoir
animalanimal human
COMMUNICABLE DISEASE
SOURCES OF INFECTION
DEFINITIONS
Hepatitis C
-Source = transfusion,
blood products
-Reservoir = humans
Examples:
Neisseria gonorrhea -Source = humans -Reservoir = humans
Salmonella typhi -Source = food/water -Reservoir = humans
Rabies virus -Source = saliva of the dog -Reservoir = the dog
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OFINFECTION:
1- AIR-BORNE
2- FOOD AND DRINK-BORNE
3- ARTHROPOD-BORNE
4- CONTACT TRANSMISSION
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OFINFECTION:
1. Water-washed dis. (Dis. of skin, eye)
2. Faecal-oral disease. (Viral, bact., parasitic)
3. Soil -mediated infections. (Tetanus, intestinal parasites)
4. Diseases of water contact. (Bilharzia, Guinea worm)
5. Food-borne dis. (F.P., intestinal flukes)
6. Infectious skin rashes. (Chickenpox, smallpox)
7. Respiratory infections. (Viral, bacterial)
8. Dis. Transmitted via body fluids. (STD)
9. Insect-borne. (Viral, parasitic)
10. Zoonoses. (Brucellosis, rabies)
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OFINFECTION:
1. Water-washed dis. (Dis. of skin, eye)
2. Faecal-oral disease. (Viral, bact., parasitic)
3. Soil -mediated infections. (Tetanus, intestinal parasites)
4. Diseases of water contact. (Bilharzia, Guinea worm)
5. Food-borne dis. (F.P., intestinal flukes)
6. Infectious skin rashes. (Chickenpox, smallpox)
7. Respiratory infections. (Viral, bacterial)
8. Dis. Transmitted via body fluids. (STD)
9. Insect-borne. (Viral, parasitic)
10. Zoonoses. (Brucellosis, rabies)
1- AIR-BORNE
2- FOOD AND DRINK-BORNE
3- ARTHROPOD-BORNE
4- CONTACT TRANSMISSION
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OFINFECTION:
COMMUNICABLE DISEASE
CHANNELS OF TRANSMISSION OFINFECTION:
1- AIR-BORNE
2- FOOD AND DRINK-BORNE
3- ARTHROPOD-BORNE
4- CONTACT TRANSMISSION
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
1- AIR-BORNE
Droplet infection (direct spread): CSM, Whooping cough Droplet nuclei (direct air-borne): Measles, Chickenpox Infected dust (indirect air-borne): TB, Diphtheria
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
1- AIR-BORNEInhalation Infections: Respiratory Tract:
• Pulmonary Tuberculosis.• Influenza• Sore-throat• Pneumonia• Common cold
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
1- AIR-BORNEInhalation Infections: Other Specific Fevers :
• Measles.• Whooping cough• Diphtheria• Scarlet fever• Chicken pox• Mumps• Rubella• Cerebrospinal fever• (Small Pox)
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNECategories:
The enteric group (salmonellae) The dysentery group (shigellae) The rotaviruses (G.E.) Hep A Cholera Food poisoning (staph). Amoebic dysentery. Helminths.
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNEMethods of transmission:
The human hand
Musca domesticaHouse fly
Flies
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNEMethods of transmission:
Milk: Excellent medium• T.B.• F.P.• Diphtheria
Dirty hands of milking manDirty bottle
Water: Very serious
Dirty udder
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
2- FOOD AND DRINK-BORNEMethods of transmission:
Meat:
• Contaminated meat.
Fresh Vegetables and Fruits : • Poor medium.• Can be contaminated by:
Flies Washing water
Dirty hands Manure
• Diseased animal
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNEMethods of transmission:
Biological transmission Harborage transmission Transovarial transmission Mechanical transmission
Can be:
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNEMethods of transmission:
Vector: Inoculation Contamination skin or mucous membranes
• By infectious feces. • Body fluids (when
crushed)
Inoc
ulat
ion
Inoculation
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNEMethods of transmission:
Flies:
• Poliomyelitis.
• Enteric fevers.
• Ascariasis.
• Mucopurulent conjunctivitis.
• Amoebic dysentery.
• Food poisoning.
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNEMethods of transmission:
The louse (Pediculum humanus):• Epidemic typhus.
• L.B. relapsing fever.
human body louse
HumanHeadlouse
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNEMethods of transmission:
The Flea (Xenopsylla cheopis; rat flea) :
Bubonic plague
Endemic typhus
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNEMethods of transmission:
The Mosquito (female of):
- Culex sp. (filariasis)
- Anopheles sp. (malaria)
- Aedes sp. (yellow fever)
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
3- ARTHROPOD-BORNEMethods of transmission:
The Sand Fly:
- Cutaneous Leishmaniasis.
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACTMethods of transmission:
Can be: • Direct • Indirect
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACTTypes:
STD• ?• Syphilis • Herpes simplex• Lymphogranuloma• (AIDS)
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACTTypes:
Fungal Infection of the skin
- Tinea capitis (ring worm).
Tinea pedis (athlete’s foot).
- Tinea cruris.(crotch itch)
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACTTypes:
Mycosis
- Moniliasis(Oral Thrush)
- Mycetoma
Madura foot
COMMUNICABLE DISEASECHANNELS OF TRANSMISSION OF INFECTION:
4- CONTACTTypes:
Scabies:
mite (Sarcoptes scabiei)
Trachoma and other eye infections.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIPEpidemiologic Triangle
Agent(Seed)
Environment
(Climate)
Host
(Soil)
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIPInfectious Disease Model
HostPathogen
Environment
disease
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP
• Biological• Physical• Chemical• Mechanical• Nutrient
Disease Agents
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Biological Disease Agents
• Bacteria • Viruses• Parasites
• Protozoa• Metazoa
• Rickettsiae• Fungi
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Microbes-humans Relationship
Very few microbes arealways pathogenic
Many microbes arepotentially pathogenic
Most microbes are
nevernever pathogenic
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Microbes-humans Relationship(Symbiosis
) Mutualism - Association in which both partners benefit Commensalism - Association in which one partner benefits
and other is unharmed Parasitism - Association in which the microbe befits at
expense of host
(Flora living on skin)
(pathogenic infection)
(Bacteria and synthesis of vitamins K and B)
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Agent Factors
- Antigenic make-up.- Growth requirements.- Ability to survive outside the host (milk, water, soil).- Viability under varying conditions (temp, humidity).- Spectrum of hosts.- Resistance to treatment.- New genetic information.
Intrinsic Properties of “Agent”
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Agent FactorsProperties subject to interaction
Infectivity
Pathogenicity
Virulence
Immunogenicity
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Agent FactorsProperties subject to interaction
Infectivity
Pathogenicity
Virulence
Immunogenicity
Dose Source Route Duration before reaching the host Host characteristics
• Age• Race• Nutritional Status
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Host Factors
• Exposure• Susceptibility• Response to the agent
( a HOST is a PERSON who can be infected under normal conditions.)
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Host FactorsExposure
• Age
• Sex
• Race
• S.E.S ( occupation)
• Behavior
• Drug abuse
• Sexual practice
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Host Factors
• Age
• Pregnancy
• Malnutrition
• Immunity
• Other diseases
• Medications
Susceptibility and Response to the Agent
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Environmental Factors
• Climate
• Geography
• Water
• Housing
1- Physical Environment
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Environmental Factors2- Biological Environment
• Agents
• Reservoirs
• Intermediate hosts
• Vectors
•Man
•Microbes
•Insects
•Rodents
•Animals
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Environmental Factors3- Psychosocial Environment
• Education• Occupation• Beliefs• Attitude• Behavior
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Reservoir of InfectionTypes :
• Most viral and bact. RTIs• Most staph and strept.• Childhood exanthemata• STD
1. Human to Human
Human
Human
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Reservoir of Infection
Zoonosis
Types :
2. Animal to Human
animalanimal human
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Reservoir of InfectionTypes :
3. Complex cycles
- Malaria- Bilharzia- Tape worm
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Infection
Initial infection ( exposure )
Sign = observable or measurable change in body function eg : rash, fever
Onset of clinical disease( symptoms or signs)
Symptom = subjective complaint e.g.: pain, loss of appetite, lethargy
The Incubation Period :
Phases of Infectious Disease :
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Infectious Disease :
Initial infection Start of infectiousness
The Period of Communicability:
2. before onset after recovery - convalescence - chronic
1. before onset early in disease course
The Latent Period :
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Infectious Disease :
Phases of Disease Cycle:Incubation period: -Variable length -Prior to signs and symptoms
Prodromal stage: - The period of early symptoms - Indicates the start of disease before specific symptoms and signs occur. - Often infectious/contagious - Innate immune response starts
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Infectious Disease :
Phases of Disease Cycle:
Decline stage: - Alleviation of signs and symptoms - Recovery/convalescence
Illness stage : - Most severe phase - Clear evidence of signs and symptoms - Acquired immune responses begin
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Infectious Disease :
Cycle of InfectionINFECTIOUS
AGENTBACTERIAVIRUSESFUNGI
PROTOZOAHELMINTH
RESERVOIRPEOPLE
EQUIPMENTWATER
PORTAL OF EXIT
EXCRETIONSSECRETIONSDROPLETS
SKINMODE OF
TRANSMISSIONAIRBOURNEINGESTION
INNOCULATIONCONTACT
PORTAL OF ENTRYBROKEN SKIN
MUCOUS MEMBRANESGIT/RESPIRATORYURINARY TRACT
SUSCEPTIBLE HOSTNEONATESDIABETICS
IMMUNOSUPPRESSEDCARDIOPULMONARY DISEASE
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Infectious Disease :
Outcome of Infection
H
O
S
T
PRASITE
COLONIZATION
C O V E R T
O V E R Tdisease
disease
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Infectious Disease :
Disease Mechanism
– Tissue invasion
– Toxin production
– Hypersensitivity
Outcome of Infection
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Infectious Disease :
Disease MechanismOutcome of Infection
Spectrum of Disease
f fff f
f fff f
f fff f
f fff f
TB, Polio, Hep A
Measles, Chickenpox
Rabies, Amebic Encephalitis, Hemorrhagic Fever.
Fatal Sever Moderate Mild Inapparent
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceSporadic Disease :
Occurs irregularly and only occasionally in a population . e.g. Typhoid fever (Salmonella typhi)
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceEndemic Disease :Constant presence of an infectious disease within a given geographical area or population group. the usual
or expected
frequency of disease
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceHyperendemic Disease :
When occurrence frequency rises,
but not to epidemic proportions.
e.g. - Common cold in the winter months - high prevalence malaria
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceEpidemic :
The occurrence of cases of disease,(( specific health related behavior, or other health related events ))
clearly more than expected In a given area
or among a specific group of people over a particular time.
? One example
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceOutbreak :
epidemic-like increase in frequency,
but in a very limited (focal) segment of the population;Usually of shorter duration.
Example: Food poisoning, URTI
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrencePandemic :
An epidemic occurring over a very wide area
(several countries or continents)and usually affecting a large proportion of the population
? One example
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceEndemic Epidemic :
Num
ber
of C
ases
of
a D
isea
se
Time
Endemic Epidemic
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceEndemic Epidemic :
Host Factors:
- Change in behavior ?
- Population movement
- Immunity
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceEndemic Epidemic :
Environmental Factors:- Adverse conditions: - War - Famine- Vector:
- Mosquitos- Flies
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease :
Levels of Communicable Diseases OccurrenceEndemic Epidemic :
Environmental Factors:
- New or Exposure - Change in climate - Irrigation scheme(- Energy plants)
- Control measures
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
I Controlling the source of infection
II Blocking the channels of transmission
III Protecting the susceptible population
Can be classified into:
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
I Controlling the source of infection : (CASES, CARRIERS AND ANIMAL RESERVOIR)
- Early diagnosis
- Notification - Isolation
- Treatment - Quarantine
- Surveillance - Disinfection
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Air- borne:
- Bed-spacing - Dust-control - Effective ventilation - Good health habits - Air disinfection - Use of masks - Minimize over-
crowding
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Food and Drink - borne:
– Provision of safe/sufficient water.– Pasteurization or boiling of milk.– Proper personal hygiene.– Sanitary sewage disposal.– Control of flies.– Washing fresh vegetables.– Meat and slaughter house control.– Refrigeration of unused food.– Control of food handlers and vendors.– Labs for food examination.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Food and Drink - borne:
FOOD DRINK BOTH FOOD and DRINK
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Arthropod - borne:
Lice:
• Personal cleanliness.
• Avoiding overcrowding.
• Dusting by insecticides.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Arthropod - borne:
Fleas:• Cleanliness of dwellings. • Avoid dust collection.• Spraying & dusting by
insecticides.• Rodent control.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Arthropod - borne:
Mosquitos :
• Vector control.
• Personal protection.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Contact Diseases:
- Case finding and treatment.
- Tracing of contacts.
- Serological examination.- Control of sexual behaviour.- Personal cleanliness.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
II Blocking the channels of transmission : Contact Diseases:
- Comb. - Hair brush. - Towels. - Handkerchief. - Underwear. - Footwear ……. etc.
- Avoid use of common articles:
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
III Protecting the susceptible population : - Primary Prevention:
- Health promotion. - Specific protection.
- Secondary Prevention: - Early diagnosis and - Prompt treatment.
- Tertiary Prevention: - Limitation of disability. - Rehabilitation.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
III Protecting the susceptible population : - Primary Prevention:
- Health promotion.
- Adequate nutrition. - Health education. - Socio-economic development.- Environmental sanitation.- Personal hygiene. (- Genetic counseling.)
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
III Protecting the susceptible population :
- Specific immunization.- Protection against occupational hazards.
- Protection against accidents.
- Protection from carcinogens.
- Avoidance of allergens.
- Primary Prevention: - Specific protection.
- Protection against occupational hazards.
- Protection against accidents.
- Protection from carcinogens.
- Avoidance of allergens.
- Protection against occupational hazards.
- Protection against accidents.
- Protection from carcinogens.
- Avoidance of allergens.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
III Protecting the susceptible population : - Secondary Prevention:
- Early diagnosis and - Prompt treatment.
- Screening for sub-clinical disease.
- Health education
- Case finding
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
III Protecting the susceptible population : - Tertiary Prevention:
- Limitation of disability.
- Rehabilitation.
- Adequate treatment.
- Psychological: - Restoration of personal confidence and independence.
- Medical: - Physical restoration of function.
COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Control of Communicable Disease :
III Protecting the susceptible population : - Tertiary Prevention:
- Rehabilitation.- Vocational: - Restoration of capacity to earn. (Occupational)
- Social: - Restoration of family and community relationship.
COMMUNICABLE DISEASE
Natural History of Disease
RecoveryRecovery
COMMUNICABLE DISEASE
Natural History of Disease
RecoveryRecovery
COMMUNICABLE DISEASE
Natural History of Disease
RecoveryRecovery
COMMUNICABLE DISEASE
Natural History of Disease
RecoveryRecovery
COMMUNICABLE DISEASE
Natural History of Disease
RecoveryRecovery