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

Control DEFINITIONS COMMUNICABLE DISEASE : EPIDEMIOLOGY PREVENTION COMMUNICABLE DISEASE : An illness due to a specific infectious agent or its toxic products. EPIDEMIOLOGY: Study of distribution and determinants of health-related states and events in specified populations and application of this study to control health problems. CONTROL : reducing occurrence of disease so that it is no longer a problem. PREVENTION : elimination of the probability that a disease will occur.

DEFINITIONS COMMUNICABLE DISEASE An illness due to a specific infectious agent or its toxic products. COMMUNICABLE DISEASE : An illness due to a specific infectious agent or its toxic products. EPIDEMIOLOGY: Study of distribution and determinants of health-related states and events in specified populations and application of this study to control health problems. CONTROL : reducing occurrence of disease so that it is no longer a problem. PREVENTION : elimination of the probability that a disease will occur.

DEFINITIONS EPIDEMIOLOGY COMMUNICABLE DISEASE 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. COMMUNICABLE DISEASE : An illness due to a specific infectious agent or its toxic products. EPIDEMIOLOGY: Study of distribution and determinants of health-related states and events in specified populations and application of this study to control health problems. CONTROL : reducing occurrence of disease so that it is no longer a problem. PREVENTION : elimination of the probability that a disease will occur.

Control: Elimination : Eradication: Extinction: DEFINITIONS COMMUNICABLE DISEASE DEFINITIONS Control: Elimination : Eradication: Extinction: 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. Example: diarrheal diseases. 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. Example: measles, poliomyelitis. Eradication: 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. Example: smallpox. Extinction: The specific infectious agent no longer exists in nature or in the laboratory. Example: none.

COMMUNICABLE DISEASE 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. 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. Example: diarrheal diseases. 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. Example: measles, poliomyelitis. Eradication: 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. Example: smallpox. Extinction: The specific infectious agent no longer exists in nature or in the laboratory. Example: none.

Elimination DEFINITIONS COMMUNICABLE DISEASE 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. 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. Example: diarrheal diseases. 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. Example: measles, poliomyelitis. Eradication: 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. Example: smallpox. Extinction: The specific infectious agent no longer exists in nature or in the laboratory. Example: none.

DEFINITIONS Eradication COMMUNICABLE DISEASE DEFINITIONS Eradication 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.. 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. Example: diarrheal diseases. 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. Example: measles, poliomyelitis. Eradication: 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. Example: smallpox. Extinction: The specific infectious agent no longer exists in nature or in the laboratory. Example: none.

DEFINITIONS Extinction COMMUNICABLE DISEASE DEFINITIONS Extinction The specific infectious agent no longer exists in nature or in the laboratory. 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. Example: diarrheal diseases. 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. Example: measles, poliomyelitis. Eradication: 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. Example: smallpox. Extinction: The specific infectious agent no longer exists in nature or in the laboratory. Example: none.

. Incubatory carrier . Convalescent carrier . Chronic carrier COMMUNICABLE DISEASE SOURCES OF INFECTIONS CASE OF DISEASE : a patient CARRIER : . Incubatory carrier . Convalescent carrier . Chronic carrier . In-apparent carrier ANIMAL RESERVOIR (ZOONOSIS) INANIMATE RESERVOIR (THE SOIL) CARRIER: A person or animal without apparent disease who harbors a specific infectious agent and is capable of transmitting the agent to others.

COMMUNICABLE DISEASE 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. CARRIER: A person or animal without apparent disease who harbors a specific infectious agent and is capable of transmitting the agent to others.

SOURCES OF INFECTIONS Reservoir: COMMUNICABLE DISEASE SOURCES OF INFECTIONS 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 CARRIER: A person or animal without apparent disease who harbors a specific infectious agent and is capable of transmitting the agent to others.

Reservoir Zoonosis animal human SOURCES OF INFECTION COMMUNICABLE DISEASE SOURCES OF INFECTION Reservoir Zoonosis animal 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: An infectious disease that is transmissible under normal conditions from animal to human animal human

SOURCES OF INFECTION Examples: Salmonella typhi Neisseria gonorrhea COMMUNICABLE DISEASE SOURCES OF INFECTION Examples: Salmonella typhi -Source = food/water -Reservoir = humans Neisseria gonorrhea -Source = humans -Reservoir = humans Hepatitis C -Source = transfusion, blood products -Reservoir = humans Rabies virus -Source = saliva of the dog -Reservoir = the dog

MODE OF TRANSMISSION OF INFECTION: COMMUNICABLE DISEASE MODE OF TRANSMISSION OF INFECTION: 1- AIR-BORNE 2- FOOD AND DRINK-BORNE 3- ARTHROPOD-BORNE 4- CONTACT TRANSMISSION

TRANSMISSION OFINFECTION: COMMUNICABLE DISEASE 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)

COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION:

CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE 2- FOOD AND DRINK-BORNE 3- ARTHROPOD-BORNE 4- CONTACT TRANSMISSION

(indirect air-borne): TB, Diphtheria COMMUNICABLE DISEASE CHANNELS 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

Caused by various strains of mycobacteria, usually Mycobacterium. COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: Pulmonary Tuberculosis Caused by various strains of mycobacteria, usually Mycobacterium. Spread through the air Most infections are asymptomatic and latent active TB infection cough, sneeze, or otherwise transmit respiratory fluids through the ai.

caused by the influenza viruses RNA viruses COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: Influenza 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.

1- AIR-BORNE Inhalation Infections: Pneumonia COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: 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.

1- AIR-BORNE Inhalation Infections: Sore-throat COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: 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. pharyngitis

1- AIR-BORNE Measles Inhalation Infections: COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: Measles 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 also known asmorbilli, English measles, or rubeola

Caused by the bacterium Bordetella pertussis COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: 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. It mainly affects infants younger than 6 months old before they're adequately protected by immunizations, and kids 11 to 18 years old whose immunity has started to fade.

1- AIR-BORNE Diphtheria Caused by Corynebacterium diphtheriae, COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 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.

COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: 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, most commonly affects 4-8 year old children. Strawberry tongue seen in scarlet fever. Red cheeks and pale area around the mouth in scarlet fever.

caused by: varicella zoster virus (VZV). COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 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. chickenpox is infectious one to two days before the rash appears.[2] They remain contagious until all lesions have crusted over (this takes approximately six days).[

1- AIR-BORNE Inhalation Infections: Mumps Caused by: the mumps virus. COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: 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 • (epidemic parotitis), is the most typical presentation The disease is generally self-limiting, running its course before receding,

Caused by the rubella virus. COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 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 ) also known as German measles. ). The virus may also be present in the urine, feces and on the skin. Infection of the mother by Rubella virus during pregnancy can be serious;

1- AIR-BORNE Cerebrospinal fever COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Cerebrospinal fever severe headaches, tenderness of the back of the neck, paralysis of the ocular muscles. characterized by inflammation of the membranes of the brain and spinal cord,

1- AIR-BORNE Inhalation Infections: Measles. Whooping cough Diphtheria COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 1- AIR-BORNE Inhalation Infections: Measles. Whooping cough Diphtheria Scarlet fever Chicken pox Mumps Rubella Cerebrospinal fever (Small Pox)

2- FOOD AND DRINK-BORNE Categories: The enterica (salmonellae) COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 2- FOOD AND DRINK-BORNE Categories: The enterica (salmonellae) The dysentery (shigellae ,Amoebic) The rotaviruses (G.E.) Hep A Cholera Food poisoning (staph). Helminths. Enterica is bacterial disease transmitted by the ingestion of food or which contain the bacterium Salmonella enterica , Dysentery is an inflammatory disorder of the intestine)( viral, bacterial, or parasitic)., Rotaviruses common cause of severe diarrhea among infants and young children caused by RNA virus in the family Reoviridae. Hepatitis A infection causes no clinical signs and symptoms in over 90% of infected children and since the infection confers lifelong immunity ,Hepatitis A is an acute infectious disease of the liver caused by the hepatitis A virus (HAV). Cholera is an infection in the small intestine caused by the bacterium Vibrio cholera. The main symptoms are watery diarrhea and vomiting . Foodborne illness usually arises from improper handling, preparation, or food storage. Goodhygiene practices before, during, and after food preparation can reduce the chances of contracting an illness. Parasitic worms, often referred to as helminths, Those that live inside the digestive tract are called intestinal parasites. They can live inside humans and other animals.

2- FOOD AND Water-BORNE Musca domestica House fly COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 2- FOOD AND Water-BORNE Methods of transmission: The human hand Flies Musca domestica House fly

2- FOOD AND DRINK-BORNE Methods of transmission: COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 2- FOOD AND DRINK-BORNE Methods of transmission: Milk: Excellent medium T.B. F.P. Diphtheria Dirty udder Dirty hands of milking man Dirty bottle Water: Very serious

2- FOOD AND DRINK-BORNE Methods of transmission: Meat: Diseased animal COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 2- FOOD AND DRINK-BORNE Methods of transmission: Meat: Diseased animal Contaminated meat. Fresh Vegetables and Fruits : Poor medium. Can be contaminated by: Flies Washing water Dirty hands Manure

3- ARTHROPOD-BORNE Methods of transmission: Can be: COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 3- ARTHROPOD-BORNE Methods of transmission: Can be: Biological transmission Harborage transmission Transovarial transmission Mechanical transmission Harborage transmission: a mode of infection transmission in which the organism does not undergo morphologic or physiologic changes in the vector.

3- ARTHROPOD-BORNE Methods of transmission: Vector: Inoculation COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 3- ARTHROPOD-BORNE Methods of transmission: Vector: Inoculation Inoculation Inoculation Contamination (broken skin or mucous membranes) By infectious feces. Body fluids (when crushed)

3- ARTHROPOD-BORNE Methods of transmission: Flies: Enteric fevers. COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 3- ARTHROPOD-BORNE Methods of transmission: Flies: Enteric fevers. Mucopurulent conjunctivitis. Ascariasis. Food poisoning. Ascariasis caused by the parasitic roundworm Ascaris lumbricoides may cause malabsorption and anorexia which contribute to malnutrition.. Poliomyelitis often called polio or infantile paralysis, is an acute, viral, infectious disease. is highly contagious via the oral-oral (oropharyngeal source) and fecal-oral (intestinal source) routes. the virus enters the central nervous system, and destroying motor neurons, leading to muscle weakness and acute flaccid paralysis. Amoebic dysentery. Poliomyelitis.

3- ARTHROPOD-BORNE Methods of transmission: COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 3- ARTHROPOD-BORNE Methods of transmission: The louse (Pediculum humanus): Epidemic typhus. L.B. relapsing fever. human body louse L.B. relapsing fever is a vector-borne disease caused by infection with certain bacteria in the genus Rickettsia and Borrelia , which are transmitted through the bites of lice or soft-bodied ticks . Human Head louse

3- ARTHROPOD-BORNE Methods of transmission: COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 3- ARTHROPOD-BORNE Methods of transmission: The Flea (Xenopsylla cheopis; rat flea) : Bubonic plague is a zoonotic disease, circulating mainly in fleas on small rodents, caused by Yersinia pestis. Swollen lymph nodes especially occur in the armpit and groin s, . Acral gangrene (i.e. of the fingers, toes, lips and nose), is another common symptom Endemic typhus

3- ARTHROPOD-BORNE Methods of transmission: The Mosquito (female of): COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 3- ARTHROPOD-BORNE Methods of transmission: The Mosquito (female of): - Culex sp. (filariasis) - Anopheles sp. (malaria) - Aedes sp. (Dengue fever) Filariasis caused by thread-like nematodes (roundworms). The most spectacular symptom of lymphatic filariasis is elephantiasis—edema with thickening of the skin and underlying tissues ,transmitted by mosquito bites.[3] Elephantiasis results when the parasites lodge in the lymphatic system.

- Cutaneous Leishmaniasis. COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 3- ARTHROPOD-BORNE Methods of transmission: The Sand Fly: - Cutaneous Leishmaniasis.

4- CONTACT Methods of transmission: Can be: Direct Indirect COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 4- CONTACT Methods 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. Diseases of Contact: Disease which are easily transmitted by physical contact with the person suffering the disease, or by their secretions or objects they touched.  

4- CONTACT Types: STD Hep.B Syphilis Herpes simplex Lymphogranuloma COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 4- CONTACT Types: STD Hep.B Syphilis Herpes simplex Lymphogranuloma HIV Herpes simplex caused by both Herpes simplex virus type 1 (HSV-1) and type 2 (HSV-2)Lymphogranuloma is a sexually transmitted disease caused by the invasive Chlamydia trachomatis .LGV is primarily an infection of lymphatics and lymph nodes.

- Tinea capitis (ring worm). COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 4- CONTACT Types: Fungal Infection of the skin - Tinea capitis (ring worm).   Tinea pedis (athlete’s foot). - Tinea cruris. (crotch itch)

4- CONTACT - Moniliasis - Mycetoma Madura foot Types: Mycosis COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 4- CONTACT Types: Mycosis - Moniliasis (Oral Thrush)   - Mycetoma Madura foot

mite (Sarcoptes scabiei) COMMUNICABLE DISEASE CHANNELS OF TRANSMISSION OF INFECTION: 4- CONTACT Types: -Scabies: mite (Sarcoptes scabiei)   -Trachoma and other eye infections.

HOST-PARASITE RELATIONSHIP COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Epidemiologic Triangle Agent (Seed)   Environment (Climate) Host (Soil)

HOST-PARASITE RELATIONSHIP Infectious Disease Model COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Infectious Disease Model Host Pathogen Environment disease  

Disease Agents Biological Physical Chemical Mechanical Nutrient COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Disease Agents Biological Physical Chemical Mechanical Nutrient  

Biological Disease Agents COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Biological Disease Agents Bacteria Viruses Parasites Protozoa Metazoa Rickettsiae Fungi  

Microbes-humans Relationship COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Microbes-humans Relationship Very few microbes are always pathogenic Many microbes are potentially pathogenic   Most microbes are never pathogenic

Microbes-humans Relationship (Symbiosis) COMMUNICABLE DISEASE HOST-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 (Bacteria and synthesis of vitamins K and B)   (Flora living on skin) (pathogenic infection)

- Ability to survive outside the host (milk, water, soil). COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Agent Factors Intrinsic Properties of “Agent” - 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.  

Infectivity Pathogenicity Virulence Immunogenicity Agent Factors COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Agent Factors Properties subject to interaction Infectivity Pathogenicity Virulence Immunogenicity Colonization : presence of microorganisms without disease at that point, without actual tissue invasion. This term applies to surfaces only, i.e., the blood cannot be colonized, and host cells with intracellular infection are not colonized. Infection: The entry and development or multiplication of an infectious agents in the body of person. Infectivity: The proportion of persons exposed to a causative agent who become infected by an infectious disease Pathogenicity: The proportion of persons infected after exposure to a causative agent, who then develops clinical disease Virulence: The proportion of persons with clinical disease, who after becoming infected, become severely ill or die. (The degree of pathogenicity) Immunogenicity: Is the ability of a particular substance to provoke an immune response  

Agent Factors HOST-PARASITE RELATIONSHIP COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Agent Factors Properties subject to interaction Infectivity Pathogenicity Virulence Immunogenicity Dose Source Route Duration before reaching the host Host characteristics   Age Race Nutritional Status

Exposure Susceptibility Response to the agent Host Factors COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Host Factors ( a HOST is a PERSON who can be infected under normal conditions.) Exposure Susceptibility Response to the agent  

Host Factors Exposure Age Sex Race S.E.S ( occupation) Behavior COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Host Factors Exposure Age Sex Race S.E.S ( occupation) Behavior Drug abuse Sexual practice  

Host Factors Age Pregnancy Malnutrition Immunity Other diseases COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Host Factors Susceptibility and Response to the Agent Age Pregnancy Malnutrition Immunity Other diseases Medications  

Climate Geography Water Housing Environmental Factors COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Environmental Factors 1- Physical Environment Climate Geography Water Housing  

Man Microbes Insects Rodents Animals Environmental Factors COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Environmental Factors 2- Biological Environment Man Microbes Insects Rodents Animals Agents Reservoirs Intermediate hosts Vectors  

Education Occupation Beliefs Attitude Behavior Environmental Factors COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Environmental Factors 3- Psychosocial Environment Education Occupation Beliefs Attitude Behavior  

Reservoir of Infection Types : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Reservoir of Infection Types : 1. Human to Human Human Human Most viral and bact. RTIs Most staph and strept. Childhood exanthemata STD 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: An infectious disease that is transmissible under normal conditions from animal to human  

Zoonosis animal human Reservoir of Infection Types : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Reservoir of Infection Types : 2. Animal to Human Zoonosis animal   animal human

- Malaria - Bilharzia - Tape worm Reservoir of Infection Types : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Reservoir of Infection Types : 3. Complex cycles - Malaria - Bilharzia - Tape worm  

Some Concepts of Infection Phases of Infectious Disease : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : The Incubation Period : Initial infection ( exposure ) Onset of clinical disease ( symptoms or signs)   Symptom = subjective complaint e.g.: pain, loss of appetite, lethargy Sign = observable or measurable change in body function eg : rash, fever

Some Concepts of Infection Phases of Infectious Disease : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : The Latent Period : Initial infection Start of infectiousness The Period of Communicability: 1. before onset early in disease course The Period of Communicability: The Person is directly or indirectly infectious to other persons or animals.   2. After onset after recovery - convalescence - chronic

Some Concepts of Infection Phases of Disease Cycle : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection 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 The innate immune system: The first line of defense, providing immediate defense against infection. It comprises the cells ( including: mast cells and phagocytes ) and mechanisms that defend the host from infection. It does not confer long-lasting or protective immunity to the host.  

Some Concepts of Infection Phases of Disease Cycle COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Disease Cycle Illness stage : - Most severe phase - Clear evidence of signs and symptoms - Acquired immune responses begin   Decline stage: - Alleviation of signs and symptoms - Recovery/convalescence

Some Concepts of Infection Phases of Infectious Disease : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : Cycle of Infection INFECTIOUS AGENT BACTERIA VIRUSES FUNGI PROTOZOA HELMINTH SUSCEPTIBLE HOST NEONATES DIABETICS IMMUNOSUPPRESSED CARDIOPULMONARY DISEASE RESERVOIR PEOPLE EQUIPMENT WATER PORTAL OF ENTRY BROKEN SKIN MUCOUS MEMBRANES GIT/RESPIRATORY URINARY TRACT PORTAL OF EXIT EXCRETIONS SECRETIONS DROPLETS SKIN MODE OF TRANSMISSION AIRBOURNE INGESTION INNOCULATION CONTACT

Some Concepts of Infection Phases of Infectious Disease : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : Cycle of Infection

Some Concepts of Infection Phases of Infectious Disease : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : Cycle of Infection PATHOGEN RESERVOIR/ SOURCE PORTAL of EXIT MODE of ENTRY PORTAL SUSCEPTIBLE HOST

COLONIZATION C O V E R T O V E R T COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : Outcome of Infection P R A S I T E H O S T COLONIZATION C O V E R T disease O V E R T disease

Tissue invasion Toxin production Hypersensitivity COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : Disease Mechanism Tissue invasion Toxin production Hypersensitivity

Some Concepts of Infection Phases of Infectious Disease : COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Infection Phases of Infectious Disease : Spectrum of Disease TB, Polio, Hep A f f f f f Measles, Chickenpox f f f f f Rabies, Amebic Encephalitis, Hemorrhagic Fever. f f f f f f f f f f Inapparent Mild Moderate Sever Fatal

Occurs irregularly and only occasionally in a population . COMMUNICABLE DISEASE HOST-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 DISEASE HOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease : Communicable Diseases Occurrence Endemic Disease : Constant presence of an infectious disease within a given geographical area or population group. the usual or expected frequency of disease

Communicable Disease : HOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease : Communicable Diseases Occurrence Hyperendemic Disease : When occurrence frequency rises, but not to epidemic proportions. e.g. - Common cold in the winter months - high prevalence malaria

Communicable Disease : HOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease : Communicable Diseases Occurrence Epidemic : 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 Disease : HOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease : Communicable Diseases Occurrence Outbreak : epidemic-like increase in frequency, but in a very limited (focal) segment of the population; Usually of shorter duration. Example: Food poisoning, URTI

Communicable Disease : HOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease : Communicable Diseases Occurrence Pandemic : An epidemic occurring over a very wide area (several countries or continents) and usually affecting a large proportion of the population ? One example

Communicable Disease : HOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease : Communicable Diseases Occurrence Endemic Epidemic : Number of Cases of a Disease Endemic Epidemic Time

Communicable Disease : HOST-PARASITE RELATIONSHIP Some Concepts of Communicable Disease : Communicable Diseases Occurrence Endemic Epidemic : Host Factors: - Change in behavior ? - Population movement - Immunity

Environmental Factors: - Adverse conditions: - War - Famine COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Communicable Diseases Occurrence Endemic Epidemic : Environmental Factors: - Adverse conditions: - War - Famine - Vector: - Mosquitos - Flies

Environmental Factors: COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Communicable Diseases Occurrence Endemic Epidemic : Environmental Factors: - New or Exposure - Change in climate - Irrigation scheme - Control measures

Can be classified into: COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Control of Communicable Disease : Can be classified into: I Controlling the source of infection II Blocking the channels of transmission III Protecting the susceptible population

- Early diagnosis - Notification - Isolation - Treatment - Quarantine COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Controlling the source of infection (CASES, CARRIERS AND ANIMAL RESERVOIR) - Early diagnosis - Notification - Isolation - Treatment - Quarantine - Surveillance - Disinfection ISOLOATION: Placement of patients in special rooms in hospital to prevent spread of infection to susceptible persons. QUARANTINE: Restriction of freedom of movement, or detention of apparently well individuals who have been exposed to infectious disease, which is imposed for the maximal incubation period of the disease, to prevent disease from entering a country. This can involve vessels or vehicles coming from infected or suspected ports or places. SURVEILLANCE: The systematic collection, analysis, interpretation, and dissemination of health data on an ongoing basis. DISINFECTION: The process of destroying pathogenic organisms on patient's objects( or rendering them inert). It is applied to non-living objects.

- Effective ventilation - Good health habits - Air disinfection COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Blocking the channels of transmission 1.Air- borne: - Bed-spacing - Dust-control - Effective ventilation - Good health habits - Air disinfection - Use of masks - Minimize over-crowding

2.Food and Drink - borne: HOST-PARASITE RELATIONSHIP COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Blocking the channels of transmission cont. 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.

HOST-PARASITE RELATIONSHIP Blocking the channels of transmission cont. COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP Blocking the channels of transmission cont. Food and Drink – borne: BOTH FOOD and DRINK FOOD DRINK

Avoiding overcrowding. Dusting by insecticides. COMMUNICABLE DISEASE HOST-PARASITE RELATIONSHIP 3.Arthropod - borne: Lice: Personal cleanliness. Avoiding overcrowding. Dusting by insecticides.

Communicable Disease : HOST-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 Disease : HOST-PARASITE RELATIONSHIP Control of Communicable Disease : II Blocking the channels of transmission : Arthropod - borne: Mosquitos : Vector control. Personal protection.

Communicable Disease : HOST-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 Disease : HOST-PARASITE RELATIONSHIP Control of Communicable Disease : II Blocking the channels of transmission : Contact Diseases : - Avoid use of common articles: - Comb. - Hair brush. - Towels. - Underwear. - Footwear ……. etc.

Communicable Disease : HOST-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 Disease : HOST-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 Disease : HOST-PARASITE RELATIONSHIP Control of Communicable Disease : III Protecting the susceptible population : - Primary Prevention: - Specific protection. - Specific immunization. - 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. - Protection against occupational hazards. - Protection against accidents. - Protection from carcinogens. - Avoidance of allergens.

Communicable Disease : HOST-PARASITE RELATIONSHIP Control of Communicable Disease : III Protecting the susceptible population : - Secondary Prevention: - Early diagnosis and - Prompt treatment. - Health education Screening for sub-clinical disease. - Case finding

Communicable Disease : HOST-PARASITE RELATIONSHIP Control of Communicable Disease : III Protecting the susceptible population : - Tertiary Prevention: - Limitation of disability. - Adequate treatment. - Rehabilitation. Psychological: Restoration of personal confidence and independence. - Medical: - Physical restoration of function.

Communicable Disease : HOST-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.

Natural History of Disease COMMUNICABLE DISEASE Natural History of Disease Recovery

Natural History of Disease COMMUNICABLE DISEASE Natural History of Disease Recovery

Natural History of Disease COMMUNICABLE DISEASE Natural History of Disease Recovery

Natural History of Disease COMMUNICABLE DISEASE Natural History of Disease Recovery

Natural History of Disease COMMUNICABLE DISEASE Natural History of Disease Recovery