communicable disease epidemiology, control & prevention mohamed m.b. alnoor chp300

COMMUNICABLE DISEASE

EPIDEMIOLOGY,CONTROL & PREVENTION

Mohamed M.B. Alnoor

CHP300


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


DEFINITIONS

COMMUNICABLE DISEASE :EPIDEMIOLOGY :

CONTROL :

PREVENTION :


DEFINITIONS

Control:

Elimination :

Eradication: Extinction:


SOURCES OF INFECTIONCASE OF DISEASE : a patient CARRIER :

. Incubatory carrier . Convalescent carrier . Chronic carrier . In-apparent carrierANIMAL RESERVOIR (ZOONOSIS)INANIMATE RESERVOIR (THE SOIL)

DEFINITIONS


SOURCES OF INFECTION

DEFINITIONS

Zoonosis

Reservoir

animalanimal human


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


CHANNELS OF TRANSMISSION OFINFECTION:

1- AIR-BORNE

2- FOOD AND DRINK-BORNE

3- ARTHROPOD-BORNE

4- CONTACT TRANSMISSION



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. 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


3- ARTHROPOD-BORNE




1- AIR-BORNE


3- ARTHROPOD-BORNE


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


1- AIR-BORNEInhalation Infections: Respiratory Tract:

• Pulmonary Tuberculosis.• Influenza• Sore-throat• Pneumonia• Common cold


1- AIR-BORNEInhalation Infections: Other Specific Fevers :

• Measles.• Whooping cough• Diphtheria• Scarlet fever• Chicken pox• Mumps• Rubella• Cerebrospinal fever• (Small Pox)


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.


2- FOOD AND DRINK-BORNEMethods of transmission:

The human hand

Musca domesticaHouse fly

Flies



Milk: Excellent medium• T.B.• F.P.• Diphtheria

Dirty hands of milking manDirty bottle

Water: Very serious

Dirty udder



Meat:

• Contaminated meat.

Fresh Vegetables and Fruits : • Poor medium.• Can be contaminated by:

Flies Washing water

Dirty hands Manure

• Diseased animal


3- ARTHROPOD-BORNEMethods of transmission:

Biological transmission Harborage transmission Transovarial transmission Mechanical transmission

Can be:



Vector: Inoculation Contamination skin or mucous membranes

• By infectious feces. • Body fluids (when

crushed)

Inoc

ulat

ion

Inoculation



Flies:

• Poliomyelitis.

• Enteric fevers.

• Ascariasis.

• Mucopurulent conjunctivitis.

• Amoebic dysentery.

• Food poisoning.



The louse (Pediculum humanus):• Epidemic typhus.

• L.B. relapsing fever.

human body louse

HumanHeadlouse



The Flea (Xenopsylla cheopis; rat flea) :

Bubonic plague

Endemic typhus



The Mosquito (female of):

- Culex sp. (filariasis)

- Anopheles sp. (malaria)

- Aedes sp. (yellow fever)



The Sand Fly:

- Cutaneous Leishmaniasis.


4- CONTACTMethods of transmission:

Can be: • Direct • Indirect


4- CONTACTTypes:

STD• ?• Syphilis • Herpes simplex• Lymphogranuloma• (AIDS)


4- CONTACTTypes:

Fungal Infection of the skin

- Tinea capitis (ring worm).

Tinea pedis (athlete’s foot).

- Tinea cruris.(crotch itch)


4- CONTACTTypes:

Mycosis

- Moniliasis(Oral Thrush)

- Mycetoma

Madura foot


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 :


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


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


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


Outcome of Infection

H

O

S

T

PRASITE

COLONIZATION

C O V E R T

O V E R Tdisease

disease


Disease Mechanism

– Tissue invasion

– Toxin production

– Hypersensitivity

Outcome of Infection


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)


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


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


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


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


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


Levels of Communicable Diseases OccurrenceEndemic Epidemic :

Num

ber

of C

ases

of

a D

isea

se

Time

Endemic Epidemic



Host Factors:

- Change in behavior ?

- Population movement

- Immunity



Environmental Factors:- Adverse conditions: - War - Famine- Vector:

- Mosquitos- Flies



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:


I Controlling the source of infection : (CASES, CARRIERS AND ANIMAL RESERVOIR)

- Early diagnosis

- Notification - Isolation

- Treatment - Quarantine

- Surveillance - Disinfection


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


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.


II Blocking the channels of transmission : Food and Drink - borne:

FOOD DRINK BOTH FOOD and DRINK


II Blocking the channels of transmission : Arthropod - borne:

Lice:

• Personal cleanliness.

• Avoiding overcrowding.

• Dusting by insecticides.



Fleas:• Cleanliness of dwellings. • Avoid dust collection.• Spraying & dusting by

insecticides.• Rodent control.



Mosquitos :

• Vector control.

• Personal protection.


II Blocking the channels of transmission : Contact Diseases:

- Case finding and treatment.

- Tracing of contacts.

- Serological examination.- Control of sexual behaviour.- Personal cleanliness.


II Blocking the channels of transmission : Contact Diseases:

- Comb. - Hair brush. - Towels. - Handkerchief. - Underwear. - Footwear ……. etc.

- Avoid use of common articles:


III Protecting the susceptible population : - Primary Prevention:

- Health promotion. - Specific protection.

- Secondary Prevention: - Early diagnosis and - Prompt treatment.

- Tertiary Prevention: - Limitation of disability. - Rehabilitation.


III Protecting the susceptible population : - Primary Prevention:

- Health promotion.

- Adequate nutrition. - Health education. - Socio-economic development.- Environmental sanitation.- Personal hygiene. (- Genetic counseling.)


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 occupational hazards.





III Protecting the susceptible population : - Secondary Prevention:

- Early diagnosis and - Prompt treatment.

- Screening for sub-clinical disease.

- Health education

- Case finding


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.


III Protecting the susceptible population : - Tertiary Prevention:

- Rehabilitation.- Vocational: - Restoration of capacity to earn. (Occupational)

- Social: - Restoration of family and community relationship.


Natural History of Disease

RecoveryRecovery

communicable disease epidemiology, control & prevention mohamed m.b. alnoor chp300

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