Airborne Vector borne Vehicle Fingers (hand to mouth) Chain of infection. environment) Direct inoculation of agents Vertical Transmission from mother

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1 Chain of Pattern of disease Reservoir Pathogen Reservoir Prevention & control of communicable disease is the disease causing agent Is the habitat in which an infectious agent normally lives & grows & multiplies. Human: cases, carriers Animal: called zoonoses Environmental: plants, soil, water Portal of exit Is the path by which an agent leaves the source host How the pathogen is passed Mode of transmission Direct transmission Direct contact of skin and mm Droplet spread (coughing- with infectious agent (in living sneezing) Transmission tissue or non - living environment) Direct inoculation of agents Vertical Transmission from mother into skin &mm (Rabies) to child through placenta (TORCH Portal of entry 1. Respiratory: sneezing- coughing 2. Gastro intestinal vomitus : cholera, or fecal discharge typhoid. 3. Genitourinary 4. Discharge of skin& mucous membrane &eye New host degree of the host s resistance Indirect transmission Airborne Vector borne Vehicle Fingers (hand to mouth) 5. In utero transmission 6. Blood 7. Others :milk & tears The new Host that accepts the pathogen. The support of pathogen life & its reproduction depend on the Pattern Definition Example Sporadic Scattered cases which are separated from each other Polio, HZV, meningococcal meningitis Endemic Constant presence (all over the year) of a disease in certain area bilharziasis in Egypt. Epidemic Sudden appearance of a dis. in certain area & in a specific time OR Cholera epidemic in Haiti A disease occurs in excess of normal expectation based on past experience in the community. Pandemic Epidemic in a country which spread to another OR Epidemic in different countries at the same time Influenza & cholera. Human case: 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) Human carrier Infected persons (having the organisms in their bodies) Apparently healthy (no symptoms) Excrete them in their discharges & disseminate s to others. Carrier 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 The following diseases have no carriers: Influenza, Measles,Herpes Zoster, Whooping Cough,T.B. Types of carrier according to 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) Types of carrier according to duration of carrier state 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 weeks up to 3 months) Chronic carrier Infective for years, Typhoid, Hepatitis B Types of carrier to discharge that carry organism outside the body Respiratory GIT Urinary Skin lesion Respiratory discharge Fecal Urine Skin lesion discharge Throat & nose: ü Diphtheria, ü Staph. Aureus Nasopharynx: ü Meningococci ü Pneumococci Small intestine: ü S. typhi ü S. paratyphi Large intestine: ü Amaebiasis S. typhi S. paratyphi Staph. aureus in food poisoning Skin diseases

2 Indirect transmission Resistance of new host Animal reservoir Types Example Animal is only reservoir of (strictly zoonotic) Plague, Brucellosis, Q fever Both man and animal are reservoir of Yellow fever, Salmonellosis, Salmonella food poising Animal are intermediate Host of Parasitic disease Hydatid disease and man is definitive host Animals may be definitive host man is affected by Taenia saginata intermediate stage of the parasite Environmental reservoir Plants Soil Agents live and multiply in soil e.g Tetanus anthrax spores - Histoplasmosis Pools of water Leigionnaires Bacillus Airborne Vehicle borne (contaminated food and drink): ü Ingestion of contaminated water, raw vegetables, fruits, milk, milk products, meat, meat products, eggs and fish ü Dust if the food is exposed to contaminated dust from man or animal excreta, it may lead to intestinal ü Human fertilization of edible crops Vector borne ü Mechanical Transmission: Houseflies and cockroaches can mechanically transmit eye & intestinal and accidental myasis ü Biological transmission: o Propagative :Yersinia pestis bacilli in rat flea o Developmental: Malaria in female anopheles o Cyclo- developmental: Filariasis in culex mosquito Fingers (hand to mouth): ü Through freshly contaminated hands and fingers by human or animal excreta. ü Auto where the patient re- infect himself as in case of entrobiasis, T.solium and intestinal tuberculosis. Human with strong immune systems are better able to fend off pathogens Human with weakened immune systems are more vulnerable to the support & reproduction of pathogens.

3 Prevention Level Nb General prevention Specific prevention Passive immunization Prevention and control 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" Stage of disease Level of prevention Type of response Pre disease Primary prevention Health promotion and specific prevention Latent disease Secondary prevention Early detection of disease Prompt proper treatment Symptomatic Tertiary prevention Disability limitation for early symptomatic disease disease Rehabilitation for late symptomatic 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. Health education Sanitary environment Health promotion Mode of transmission Food &milk sanitation Good nutrition Methods for protection Rural and town planning. Sanitary and healthy living importance of Air sanitation conditions and healthy life immunization. Prevention of over- crowdness and good style ventilation. Sanitary water supply. Sanitary disposal of sewage and refuse. Chemoprophylaxis Immunization Active immunization (vaccination). Passive immunization (Seroprophylaxis Definition 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 ). Types: Animal or human preparation: Human immunoglobulin Animal (equine) preparation (heterologous): Relatively expensive and not constantly Disadvantages Given in large doses. available. Gives short protection (1-2 weeks), It may lead to sever hypersensitivity reaction, due to exposure to animal protein. Used in small doses. Advantages relatively cheap & usually Longer period of protection ( days). available. Safe, as it does not lead to hypersensitivity reactions. Normal human immunoglobulins (NHI) Types antitoxic sera e.g. in diphtheria, Specific human immunoglobulins (SHI): or tetanus, antisnake sera, and specific hyperimmunoglobulins: antiviral sera as anti- rabies serum

4 NHI SHI Chemo prophylaxis Control 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. Prepared from donors who have been vaccinated against communicable diseases or carriers of specific s. Uses: Hepatitis B virus (HBIG) ml/kg to be repeated after 1 month and 3 months Varicella zoster (VZIG) Rabies 20u/kg unit. Tetanus 250 units for prophylaxis and units for therapy instead of antitoxic sera of animals to reduce complications. It is a specific protection of individuals by giving them antimicrobial drug which may be specific antibiotics, anti- malarial, antituberculous,antileprotic, antitrypanosomiasis Drug Indication Tetracyclin 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 for prevention of malaria among travelers to and primaquine Long acting penicillin endemic areas 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 Prevention of diseases at the primary level (primary prevention): measures to be taken to healthy individuals before the onset of diseases. Control At the secondary level (2ry prevention) means the measures which should be followed after occurrence of diseases to eliminate the spread of diseases and prevent complication. 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 Financial burden to the community. 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) (II) contacts (III) (III) environment

5 Control of cases Control of carrier Control of animal reservoir Control of contact 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 à to shorten the course of the disease. Community à 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 to others. 5) Dis Dis 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 dis. 6) Release: After clinical cure as in measles Laboratory cure with repeated release cultures as in diseases with convalescent carrier e.g. Diphtheria, cholera, typhoid. After 1-2 days of specific proper antibiotics as in meningitis and streptococcal. 7) Follow up for disability limitation and rehabilitation Detection of carrier Examination of contacts Pre- employment examination Trace the source of 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. Control measures applied to animal reservoir in case of zoonotic diseases: Ø Control of cattle and sheep by sanitary environment, good nutrition, veterinary care, immunization, milk and meat sanitation Ø Eradication of stray dogs, cats and rodents. Ø Quarantine measures for imported animal. Ø Protective clothes and precaution for those who are working with animal. Ø Destruction of infected animals (in rabies, plague) Ø Inspection or slaughtering (in bovine tuberculosis) Ø Testing and Immunization (in brucellosis) 1) 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

6 Control of droplet Control of food borne Control of arthropod Control of contact Epidemic measure International measure 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 to others as food handlers in diphtheria. 6) Isolation of contacts of pneumonic anthrax & pneumonic plague for maximum I.P. 7) Health education 8) Release after examination clinically and laboratory to be sure that they are free from. Adequate ventilation, prevention of over crowdness. Air sanitation and dis of air if needed. Dust control Health education Mass immunization: It is important to raise the vaccination coverage % in order to achieve disease eradication as in small pox. 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. 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 Control of animal as a source. Health education about personal cleaning washing hands, not to use clothes of others. Control of flies Control of STD, skin and eye. Control of rabies and tetanus. Mass immunization as in tetanus compulsory vaccination. It 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. 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. Quarantine days Small pox 14 days Cholera 5 days Plague 6 Days Yellow fever 6 days Epidemic Relapsing Fever 9 days Epidemic Typhus 12 days

7 International vaccine For imported Goods For Imported animals Concept Disability limitation International measures for infectious disease International certificate of vaccination is required only for yellow fever Poliomyelitis vaccine for travelers from endemic areas to polio free countries Other diseases e.g cholera- typhoid HAV International vaccination for Pilgrims:tetravalent meningococcal vaccine (A,C,Y,W- 135) Raw wool, hides, hair, shaving brushes made of natural bristles for prevention of anthrax (Authorized dis certificate) Monkeys :yellow fever Psittacine birds: for psittacosis Cattle: for rift valley fever Dogs 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. The objective of this intervention is to prevent the transmission of the disease process from impairment to handicap