أعوذ بالله من الشيطان أعوذ بالله من الشيطان الرجيمالرجيم

O you O you who who

believe! believe! Ward off Ward off yourselvyourselv

eses

يا أيها يا أيها ” ” الذين آمنواالذين آمنوا

قوا قوا أنفسكم .. أنفسكم ..

التحريم التحريم اآلية . اآلية . - - 66 ” ”

Prevention and Control of

Communicable Diseases

ILOs To be familiar with the chain of infection

To understand the concepts of prevention and control of infectious diseases

To understand the practical tools for prevention for prevention and control

Chain of infection

Chain of Infection

PathogenPathogen

- - is the disease causing agent

Infectious Disease Parasitic Diseases

Bacterial Viral Intestinal Protozoa Helminthic

Enterica (Typhoid and paratyphoid fevers).

Cholerafood poisoning Salmonellosis, Shigellosis and diarrheal disease of children.

Poliomyelitis, Virus A Hepatitis. Diarrhea disease of children rotavirus is the commonest).

Entameba Histolytica, Balantidium coli and Giardia Lamblia)

Ascariasis, taeniasis entrobius

vermicularis, hydatid

Chain of Infection

• is the habitat in which an infectious agent normally lives & grows & multiplies.

• Human: cases, carriers

• Animal: called zoonoses

• Environmental: plants, soil, and water

PathogenReservoirReservoir

Chain of Infection

• is the path by which an agent leaves the source host

PathogenReservoir

PortalPortalof exitof exit

Chain of Infection

Modes of Transmission Direct - Direct contact - Droplet spread Indirect - Airborne - Vehicle borne - Vector borne

Pathogen - how pathogens are passedReservoir

Portalof exit Trans-Trans-

missionmission

Chain of Infection

PathogenReservoir

Portalof exit Trans-

mission

- agent enters susceptible host

PortalPortalof entryof entry

RespiratoryOralSkin

IntravenousGastrointestinal

Chain of Infection

PathogenReservoir

Portalof exit Trans-

mission

- Final link isa susceptible host

Portalof entry

NewNewHostHost

AGENT IN RESERVOIROR SOURCE

SUSCEPTIBLE POPULATION

MODE OF TRANSMISSION

Patterns of disease occurrence in communities

Sporadic:

Scattered cases which are separated from each otherExample:Polio, HZV, meningococcal meningitis.

Constant presence (all over the year) of a disease in certain area e.g. bilharziasis in Egypt.

Endemic:

Epidemic:

Sudden appearance of a dis. in certain area & in a specific time OR A dis. occurs in excess of normal expectation based on past experience in the community.

cholera epidemic in Haiti

Epidemic in a country which spread to another OR

Epidemic in different countries at the same time, as influenza & cholera.

Pandemic: (Epidemic in more than one country)

1st - The Infectious Agent1st - The Infectious Agent

-any disease-causing microorganism (pathogen)

2nd - The Reservoir Host2nd - The Reservoir Host

- habitat in which an infectious agent normally

lives, grows, and multiplies

Human (case,carrier)

AnimalEnvironment

Human Reservoir

(1) Cases:

-Typical cases: A case suffering from an infectious disease, discharges microorganism, and is a source of microorganism.

Atypical cases: : A case which cannot be easily diagnosed or isolated (poliomyelitis and Cerebrospinal Meningitis)

Which is more dangerous ????

Typical or atypical case

Mild/moderate case or severe case?

• Infected persons (having the organisms in their bodies)• Apparently healthy (no symptoms) • Excrete them in their discharges & disseminate infections to

others.

(2) Carriers:

Carriers are dangerous because:

(1) No clinical manifestation

(2) Larger NUMBER than cases.

(3) Not diagnosed (NOT known to others)

(4) Dangerous occupations, e.g. food handlers (typhoid carrier) & school personnel (meningitis carrier)

(5) Infective for a long time, even for life e.g. HIV, typhoid & HBV

According to

1) Relation to the case 2) Period of carrier state3) Foci of infection4) Discharges that carry organism outside body5) Flow of organisms outside body. Continuous or intermittent

Classification of carriers:

The following diseases have no carriers: - Influenza - Measles - Herpes Zoster - Whooping Cough - T.B.

(1) According to relation to the case:

Incubatory carrier Infective during lP, e.g. Cholera, Hepatitis A

Convalescent carrier Infective during recovery, e.g. Cholera , Typhoid, (clinical but not bacteriological recovery)

Contact carrier Contact with a case

Healthy carrier Contact of polluted environment (contaminated food, water or soil)

Transient carrier Infective for days (last days of I.P): cholera

Temporary carrier Infective for few weeks up to few months (viral B hepatitis 3 ws up to 3 ms)

Chronic carrier Infective for years, Typhoid, Hepatitis B

(2) According to duration of carrier state:

Respiratory GIT Urinary

Throat & nose:• Diphtheria, • Staph. AureusNasopharynx:• Meningococci • Pneumococci

Small intestine: • S. typhi • S. paratyphi

Large intestine: • Amaebiasis

S. typhi paratyphi

(3) According to foci of infection

(4) According to discharge that carry organism outside the body

Skin lesion

Respiratory discharges

Faecal Urine Skindischarges

•Staph. aureus in food poisoning

•Skin diseases

2. Animal Reservoir

1. Animal is only reservoir of infection (strictly zoonotic) as in plague- Brucellosis- Q fever

2. Both man and animal are reservoir of infection Yellow fever –salmonellosis and salmonella food poising

3. Animal are intermediate Host of Parasitic disease and man is definitive host Hydatid disease

4. Animals may be definitive host man is affected by intermediate stage of the parasite as Taenia saginata

3. Environmental Reservoir

Plants –soil –waterSoil: Agents live and multiply in soil e.g Tetanus –anthrax spores - HistoplasmosisPools of water: Leigionnaires Bacillus

3rd - The Portal of Exit3rd - The Portal of Exit-Route of escape of the pathogen from the

reservoir.1.Respiratory:sneezing-couging2.Gastro intestinal vomitus cholera, or fecal discharge typhoid.3.Genitourinary 4.Discharge of skin& mucous membrane &eye5.In uetro transmission6.Blood7.Others :milk & tears

4th - The Route of Transmission4th - The Route of Transmission

-Method by which the pathogen gets from the reservoir to the new host

Modes of Transmission Direct - Direct contact of skin and mm with infectious agent (in living tissue or non living environment) - Droplet spread (coughing-sneezing)-Direct inoculation of agents into skin &mm (Rabies)-Vertical Transmission from mother to child through placenta (TORCH) Indirect - Airborne - Vehicle borne - Vector borne -Fingers (Hand to mouth)

Mod

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f Tra

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Methods of transmission

• Fingers ( hand to mouth):Through freshly contaminated hands and fingers by

human or animal excreta.

Auto infection where the patient re-infect himself as in case of entrobiasis, T.solium and intestinal tuberculosis.

Vehicle-borne:Contaminated food and drink

-Ingestion of contaminated water, raw vegetables, fruits, milk,milk products, meat, meat products, eggs and fish.

-Dust if the food is exposed to contaminated dust from man or animal excreta, it may lead to intestinal infection.

-Human fertilization of edible crops  

Vector Borne Indirect Transmission• Mechanical Transmission: Houseflies and

cockroaches can mechanically transmit eye & intestinal infection and accidental myasis].

• Biological transmission:Propagative :Yersinia pestis bacilli in rat flea

Developmental: Malaria in female anopheles

Cyclo-developmental:Filariasis in culex mosquito

Wat

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Tra

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issi

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Cryptosporidium parvum?

Wat

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Tra

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issi

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Giardiasis from water.

Foo

dbor

ne T

rans

mis

sion

Balantidium coli

5th - The Portal of Entry5th - The Portal of Entry

-Route through which the pathogen enters its new host

6th - The6th - The Susceptible HostSusceptible Host

-The new Host that accepts the pathogen

The support of pathogen life & its reproduction depend on the degree of the host’s resistance.

Human with strong immune systems Human with strong immune systems are better able to fend off pathogens. are better able to fend off pathogens.

Human with weakened immune systems Human with weakened immune systems are more vulnerable to the support & are more vulnerable to the support &

reproduction of pathogens.reproduction of pathogens.

Chain of Infection

Principles of prevention and control of infectious

diseases

Prevention

Concepts of prevention

• The goals of medicine are to promote health, to preserve health, to restore health when it is impaired, and to minimize suffering and distress.

• These goals are embodied in the word "prevention"

Levels of Prevention

Stage of disease Level of prevention Type of response

Pre-disease Primary Prevention Health promotion and Specific protection

Latent Disease Secondary prevention •Early detection of disease• Prompt and appropriate treatment

Symptomatic Disease Tertiary prevention •Disability limitation forearly symptomatic disease•Rehabilitation for lateSymptomatic disease

• Primordial prevention consists of actions to minimize future hazards to health and hence inhibit the establishment factors (environmental, economic, social, behavioural, cultural) known to increase the risk of disease.

• It addresses broad health determinants rather than preventing personal exposure to risk factors, which is the goal of primary prevention. Thus, outlawing alcohol in certain countries would represent primordial prevention, whereas a campaign against drinking and would be an example of primary prevention.

• Examples of primordial include improving sanitation (such that exposure

to infectious agents does not occur), establishing healthy communities, promoting a healthy lifestyle in childhood (for example, through prenatal nutrition programs and supporting early childhood development programmes), or developing green energy approaches. Similarly, increasing sports programmes in schools may help reduce obesity in the subsequent generations.

• As these are all population-level programmes, primordial prevention is conceptually linked to population health and health promotion, but clinicians can play a role bringing problems to notice and advocating for action on determinants.

Primary prevention

Specific preventionGeneral prevention

Achieved by

Health education

Environmental sanitation

Health promotion

Immunization and seroprophylaxis

chemoprophylaxis

1.Health education: - Mode of transmission - Methods for protection and importance of immunization.2. Sanitary environment : - Rural and town planning. - Air sanitation, prevention of over-crowdness and good

ventilation. - Sanitary water supply. - Sanitary disposal of sewage and refuse. - Food &milk sanitation.3. Health promotion : - Good nutrition - Sanitary and healthy living conditions and healthy life style.

General prevention

B-Specific prevention: The specific preventive measures including I-Immunization

- Active immunization (vaccination).

- Passive immunization (Seroprophylaxis)

2-Chemoprophylaxis

Time Vaccine Dose Route

At birth, the zero dose OPV (Sabin)BCG

2 drops0.05 ml

OralIntradermal Upper left arm

2nd , 4th , 6th months(1st , 2nd,3rd doses)

OPV (Sabin), DPTHB vaccine

2 drops0.5 ml0.5 ml

OralIM, Outer left mid-thighIM, Outer right mid-thigh

9th month Vitamin AOPV (Sabin), Booster dose

Capsule2 drops

Squeezed in mouthOral

12th month MMROPV (Sabin), Booster dose

0.5 ml 2 drops

S.C left upper armOral

18 month OPV (Sabin), Booster dose DPT, Booster dose

MMRVitamin A

2 drops0.5ml,0.5ml2 capsules

OralI.MS.CSqueezed in mouth

School entry Age (5-6 years)

OPV (Sabin)DT, Booster dose

BCG

Meningococcal vaccine

2 drops0.5ml,0.05 ml

0.5ml

OralI.MIntradermal Upper left armFor tuberculin nonreactorsS.C

Egyptian schedule of compulsory vaccination of infants and children

April 21, 2023 48

Schedule of non compulsory vaccinations

1. Pregnant women :Tetanus toxoid:

2. Food handlers :

- TAB vaccine against typhoid and paratyphoid.

- Hepatitis A vaccine.

3. Military groups:

- Tetanus toxoid

- Meningococcal polysaccharide vaccine

- BCG for non reactors.

4. International Immunization:

*Cholera vaccine: for travelers coming from or going into endemic area & should have valid vaccination certificate (6 days- 6months).

*Yellow fever vaccine: for travelers coming from or going to endemic area (Yellow fever belt) -validity (10days -10 years).

*Meningococcal vaccine for pilgrims

April 21, 2023 49

April 21, 2023 50

Passive Immunization (Seroprophylaxis)•Transfer of pre-synthesized elements of immune system to a person so that the body does not need to produce these elements itself.

•Importance: It gives rapid but temporary protection, without sensitization of memory cells. Some cellular immunity is protective against intracellular bacteria, virus, fungi or protozoa.

• Uses: prophylaxis & treatment (before or after exposure to infection).•Types: Animal or human preparation:

Human immunoglobulin (Homologous): prepared from human sources

Disadvantages: relatively expensive and not constantly available.

Advantages:

-Used in small doses.

-longer period of protection ( 30-50 days).

-Safe, as it does not lead to hypersensitivity reactions.

Animal (equine) preparation (heterologous): Anti-sera prepared in animal (horses) against some diseases. Disadvantages:

-Given in large doses.

-Gives short protection (1-2 weeks),

-It may lead to sever hypersensitivity reaction, due to exposure to animal protein. Advantages: relatively cheap & usually available.

Types: antitoxic sera e.g. in diphtheria, tetanus, antisnake sera, and antiviral sera as anti-rabies serum.

Types:

1- Normal human immunoglobulins (NHI):Prepared from large pool of plasma volunteers in endemic area.

The donor should be free from hepatitis B and C and HIV viruses.

Uses:

It is effective in prophylaxis of measles, rubella, poliomyelitis and viral A hepatitis and rubella.

*Seroprevention; if given on early exposure and proper dose.

*Seroattenuation; if late exposure or smaller dose.

2- Specific human immunoglobulins (SHI): or specific hyperimmunoglobulins:Prepared from donors who have been vaccinated against communicable diseases or carriers of specific infections.

Uses:

*Hepatitis B virus (HBIG) 0.5-5 mL/kg to be repeated after 1 month and 3 months

* Varicella zoster infection (VZIG)

* Rabies 20u/kg unit.

*Tetanus 250 units for prophylaxis and 3000 - 6000 units for therapy instead of antitoxic sera of animals to reduce complications.

2- Chemoprophylaxis:

It is a specific protection of individuals by giving them antimicrobial drug which may be specific antibiotics, anti-malarial, antituberculous,antileprotic,

antitrypanosomiasis

When ?

Just before exposure or immediately after exposure to infection.

Drug IndicationTetracyclin for household contact of cholera

Isonicotinic acid hydrazide Tuberculin positive house hold contacts

Sulphadiazine for house hold contact (4 days) in case of meningitis

Rifampicin replace sulphadiazine in resistant strains of meningitis to the contacts of cases

*Chloroquine, Mefloquine, Doxycychline, Malarone and primaquine

for prevention of malaria among travelers to endemic areas

Long acting penicillin for secondary prevention of cases of Rheumatic fever and Rheumatic heart diseases

Disadvantages of chemoprophylaxis

*Temporary protection effect STOP when drug stop.

*Highly expensive in relation to value and protection (cost benefit).

* Cannot be applied on large scale as a mass preventive measure but it is given only on limited scale to at risk groups.

*Drug toxicity if prolonged use.

*Drug resistance strain due to massive drug abuse.

*Drug allergy as in case of penicillin.

*Suppress the immune response as it kills the antigen and normal intestinal flora.

Prevention vs Control

Control• Why do community need to control diseases?

Disease control describes ongoing operations aimed at reducing:– Incidence of disease

– Duration of disease &consequently the risk of transmission

– Physical and psychosocial complications of infection

– Financial burden to the community.

Control of infectious diseases (the 4 “C”s

Control

Cases Contacts Carriers Community

Early case finding & specific ttt notificationisolation

disinfectiontreatmentfollow uprelease

Observation detection EpidemiologicalInvestigation &containment

standardstrictprotective

•Measures designed to prevent further spread of the disease from infected individuals.

•They are followed in order to attack the three epidemiological factors of the infectious cycle namely: (I) reservoir(case-carrier-animal) (II) contacts & (III) environment.

Ia) Control of Cases:1) Early case finding - The most important control measure of diseases.- Case finding by clinical examination & confirmed by laboratory investigation.2) Proper and specific treatment: - Patient to shorten the course of the disease. - Community to minimize the period of communicability. 3) Notification - To local health authorities is necessary for all infectious disease. -To WHO in case of quarantinable diseases (Cholera, yellow fever and plague) - Importance: to trace the source & channel of transmission and also for statistical purposes & the surveillance system followed by MOH. 4) Isolation of cases: •Separation of infected persons from those not infected for the period of communicability.•to eliminate the probability of spread of infection to others.

5- Disinfection Disinfection of the infective discharge of the patient or the solid articles in order to destroy the pathogenic organisms outside the body. Types: concurrent (bedside) and terminal disinfection.6-Release: •After clinical cure as in measles • Laboratory cure with repeated release cultures as in diseases with convalescent carriers e.g. Diphtheria, cholera, typhoid. •After 1-2 days of specific proper antibiotics as in meningitis and streptococcal infection.

7-Follow up for disability limitation and rehabilitation.

Ib) Carriers

Detection of carrier Examination of contacts pre-employment Trace the source of infection investigation of out breaks.Exclusion from work till cure: Periodic laboratory investigation and release after bacteriologic cultures. Health education In chronic resistant carrier (typhoid )as in chronic cholecyctitis surgical cholecystectomy.

MCQ

Ic.) AnimalsControl measures applied to animal reservoir in case of zoonotic diseases:

•Control of cattle and sheep by sanitary environment, good nutrition, veterinary care, immunization, milk and meat sanitation•Eradication of stray dogs, cats and rodents.

•Quarantine measures for imported animal.•Protective clothes and precaution for those who are working with animal.•Destruction of infected animals (in rabies, plague)

•Inspection or slaughtering (in bovine tuberculosis) •Testing and Immunization (in brucellosis)

II.Contacts1) Enlistment, 2) Investigation of contacts.3) Specific protection either by immunization or chemoprophylaxis:•Contact who immunized before, booster dose of vaccine is given as diphtheria and tetanus toxoid.•Primary vaccination (early exposure) measles in the first 3 days immunity develops after 7 days before the I.P ( l0days).•Immunoglobulin in case of exposure :measles or chicken pox. •Chemoprophylaxis as in contacts of meningococcal meningitis, gonorrhea and cholera.4) Surveillance: for maximum IP.5) Segregation where contacts are excluded from work for maximum IP to prevent spread of infection to others as food handlers in diphtheria.6) Isolation of contacts of pneumonic anthrax & pneumonic plague for maximum I.P.7) Health education8) Release after examination clinically and laboratory to be sure that they are free from infection.

III. Immediate environment:_Control of infection in a community should include control of environmental factors according to the mode of transmission in order to block the chain of infection which lead to endemicity of diseases.For example:*Control of droplet infection

•Adequate ventilation, prevention of over crowdness.• Air sanitation and disinfection of air if needed.• Dust control•Health education•Mass immunization: It is important to raise the vaccination coverage 90-100% in order to achieve disease eradication as in small pox.

Control of food borne infection•Food sanitation, regulation of food handlers.•Sanitary water supply and storage.•Sanitary sewage disposal and refuse control.•Insect and rodent control•Health education•Mass immunization in case of threatened epidemics or outbreaks.

Control of Arthropod infection•Eradication and control of adult insects.•Eradication of breeding places of the insects.•Eradication of rodents.•Control the animals as a combined reservoir with man•Immunization and epidemic measures•Protection of man from adult insects

IV. Epidemic measuresIt is large scale control to be followed during epidemics or outbreaks:•General sanitary environment or additional measures during epidemics.•Specific protection e.g. mass immunization or chemoprophylaxis.•Epidemic investigation to trace source of infection.

•Health awareness of the public about mode of transmission and protection.

•Drastic measures: this is required in case of epidemics or outbreaks e.g. closure of operating theatre in hospital in case of tetanus or gas gangrene and closure of schools or any public places as in meningococcal meningitis.

Control of contact infection•Control of animal as a source infection.•Health education about personal cleaning washing hands, not to use clothes of others. •Control of flies•Control of STD, skin and eye infection.•Control of rabies and tetanus.•Mass immunization as in tetanus compulsory vaccination.

V. International Measures for Infectiuos diseases

• International travelers: Quarantine• For SIX infectious diseases

Small pox 14 days

Cholera 5 days

Plague 6 Days

Yellow fever 6 days

Epidemic Relapsing Fever 9 days

Epidemic Typhus 12 days

Other diseases added by WHO e.g Dengue Fever & swine Flu

a.International vaccination requirement :

1. International certificate of vaccination is required only for yellow fever

Yellow Fever Validity of vaccinationFrom For

1. Primary vaccination2. Revaccination

10 daysAt once

10 years10 years

2. Poliomyelitis vaccine for travelers from endemic areas to polio free countries3. Other diseases e.g cholera- typhoid -HAV

4. International vaccination for Pilgrims:tetravalent meningococcal vaccine (A,C,Y,W-135)

b. For imported GoodsRaw wool, hides, hair, shaving brushes made of natural bristles for prevention of anthrax (Authorized disinfection certificate)

c. For Imported animals:Monkeys :yellow feverPsittacine birds: for psittacosisCattle: for rift valley feverDogs and cats: quarantine is required by some countries where rabies has been eradicated

Tertiary prevention

• It is used when the disease process has advanced beyond its early stages.

• It is defined as “all the measures available to reduce or limit impairments and disabilities, and to promote the patients’ adjustment to irremediable conditions.”

• Intervention that should be accomplished in the stage of tertiary prevention are disability limitation, and rehabilitation.

Disability limitationThe objective of this intervention is toprevent the transmission of the diseaseprocess from impairment to handicap RF RHD

limited activity

unemployed

disease

impairment

disability

handicap