communicable diseases epidemiology, control & prevention chp300

COMMUNICABLE DISEASES

EPIDEMIOLOGY,CONTROL & PREVENTION

CHP300

COMMUNICABLE DISEASE

Content

Sources & transmission 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


An illness due to a specific infectious agent

or its toxic products.


DEFINITIONS

EPIDEMIOLOGY

Study of distribution and determinants of

health-related states and events in

specified populations and application of

this study to control health problems.


DEFINITIONS

Control:

Elimination :

Eradication: Extinction:


DEFINITIONS

Control

The reduction of disease incidence,

prevalence, morbidity or mortality to a locally

acceptable level as a result of deliberate

efforts; continued intervention measures are

required to maintain the reduction.


DEFINITIONS

Elimination

Reduction to zero of the incidence of infection

caused by a specific agent in a defined

geographical area as a result of deliberate

efforts; continued measures to prevent re-

establishment of transmission are required.


DEFINITIONS

Permanent reduction to zero of the worldwide

incidence of infection caused by a specific agent

as a result of deliberate efforts; intervention

measures are no longer needed..

Eradication


DEFINITIONS

The specific infectious agent no longer

exists in nature or in the laboratory.

Extinction


CASE OF DISEASE : a patient CARRIER :

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

SOURCES OF INFECTIONS


CARRIER :

A person or animal without apparent

disease who harbors a specific

infectious agent and is capable of

transmitting the agent to others.



Reservoir:

Any person, animal, arthropod, plant, soil or

substance (or combination of these) in which an

infectious agent lives and multiplies, on

which it depends primarily for survival,

and where it reproduces itself, in such a

manner that it can be transmitted to a

susceptible host



Zoonosis

Reservoir

animalanimal human

SOURCES OF INFECTION


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

SOURCES OF INFECTION


MODE OF TRANSMISSION OFINFECTION:

1- AIR-BORNE

2- FOOD AND DRINK-BORNE

3- ARTHROPOD-BORNE

4- CONTACT TRANSMISSION


TRANSMISSION OFINFECTION:

1. Water-washed dis. (Dis. of skin, eye)

2. Fecal-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. Zoonosis. (Brucellosis, rabies)


CHANNELS OF TRANSMISSION OFINFECTION:

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:

• Caused by various strains of

mycobacteria, usually Mycobacterium.

• Spread through the air

• Most infections are asymptomatic and

latent

Pulmonary Tuberculosis


1- AIR-BORNEInhalation Infections:Influenz

a• caused by the influenza viruses RNA

viruses

• The most common symptoms are chills,

fever, runny nose, sore throat, muscle

pains, headache (often severe), coughing,

fatigue and general discomfort.



Pneumonia

•Is an inflammatory condition of the lung

•Caused by infection with viruses or bacteria and

less commonly other microorganisms .

•Typical symptoms include a cough, chest pain,

fever, and difficulty breathing.



Sore-throat

•Inflammation of the pharynx caused by a viruses&

bacteria (group A streptococcus).

•Discomfort, pain, or scratchiness in the throat. It

often makes it painful to swallow.



• an infection of the respiratory system and is

highly contagious ,caused by a paramyxovirus

• Symptoms include fever, cough, runny nose, red

eyes and a generalized,confluent

maculopapular, and erythematous rash.

Measles



Whooping cough:

•Caused by the bacterium Bordetella pertussis

•The first symptoms are similar to those of a

common cold .

• It's characterized by severe coughing spells.


1- AIR-BORNE

Diphtheria

• Caused by Corynebacterium diphtheriae,

• Spread by direct physical contact or breathing

• Characterized by sore throat, low fever, and an

adherent membrane on the tonsils, pharynx.

• consequences myocarditis and peripheral

neuropathy.



Scarlet fever

•caused by toxin , produced by the bacterium

Streptococcus pyogenes (group A strep)

•complications such as glomerulonephritis and

endocarditis leading to heart valve disease,


1- AIR-BORNE

Chicken pox

•caused by: varicella zoster virus (VZV).

•Spread: coughing or sneezing or direct contact

with secretions from the rash

•Symptoms :vesicular skin rash also ulcers in

the oral cavity and tonsil areas.



Mumps

•Caused by: the mumps virus.

•Painful swelling of the salivary glands (the parotid

gland) ,Painful testicular swelling (orchitis). Fever ,

headache , malaise and anorexia.

•complications such as infertility or subfertility


1- AIR-BORNE

Rubella :

•Caused by the rubella virus.

• Transmitted via airborne droplet (Acquired)or

if the mother is infected within the first 20

weeks of pregnancy, the child may be born with

congenital rubella syndrome (trans placental )


1- AIR-BORNE

Cerebrospinal feversevere headaches, tenderness of the back of the neck, paralysis of the ocular muscles.



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


2- FOOD AND DRINK-BORNECategories:

The enterica (salmonellae) The dysentery (shigellae ,Amoebic) The rotaviruses (G.E.) Hep A Cholera Food poisoning (staph). Helminths.


2- FOOD AND Water-BORNEMethods of transmission:

The human hand

Musca domesticaHouse fly

Flies


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


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


3- ARTHROPOD-BORNEMethods of transmission:

Biological transmission Harborage transmission Transovarial transmission Mechanical transmission

Can be:



Vector: Inoculation Contamination (broken 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. (Dengue fever)



The Sand Fly:

- Cutaneous Leishmaniasis.


4- CONTACTMethods of transmission:

Can be:

• Direct • Indirect

• Disease which are easily transmitted by physical contact with the person suffering the disease, or by their secretions or objects they touched.


4- CONTACTTypes:

STD• Hep.B• Syphilis • Herpes simplex• Lymphogranuloma• HIV


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.


HOST-PARASITE RELATIONSHIP

Epidemiologic 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. After onset after recovery - convalescence - chronic

1. before onset early in disease course

The Latent Period :

COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Some Concepts of InfectionPhases of Disease Cycle :

Incubation period: -Variable length -Prior to signs and symptomsProdromal 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 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


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 :

Communicable Diseases Occurrence:Sporadic Disease :

Occurs irregularly and only occasionally in a population . e.g. Typhoid fever (Salmonella typhi)


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 Diseases OccurrenceHyperendemic Disease :

When occurrence frequency rises,

but not to epidemic proportions.

e.g. - Common cold in the winter months - high prevalence malaria


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 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 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 Diseases OccurrenceEndemic Epidemic :

Num

ber

of C

ases

of

a D

isea

se

Time

Endemic Epidemic


Communicable Diseases OccurrenceEndemic Epidemic :

Host Factors:

- Change in behavior ?

- Population movement

- Immunity


Endemic Epidemic :

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

- Mosquitos- Flies

Communicable Diseases Occurrence

COMMUNICABLE DISEASEHOST-PARASITE RELATIONSHIP Communicable Diseases Occurrence

Endemic Epidemic :

Environmental Factors:

- New or Exposure - Change in climate - Irrigation scheme

- Control measures


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:


(CASES, CARRIERS AND ANIMAL RESERVOIR)

- Early diagnosis

- Notification - Isolation - Treatment - Quarantine - Surveillance - Disinfection

Controlling the source of infection


1.Air- borne: - Bed-spacing - Dust-control - Effective ventilation - Good health habits - Air disinfection - Use of masks - Minimize over-

crowding

Blocking the channels of transmission


2.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.

Blocking the channels of transmission cont.


FOOD DRINK BOTH FOOD and DRINK

Blocking the channels of transmission cont.

Food and Drink – borne:


3.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.


II Blocking the channels of transmission : Arthropod - borne:

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. - 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 diseases epidemiology, control & prevention chp300

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