Lecture 1 Public Health (Community Medicine) PDF

Public health (COMMUNITY MEDICINE) Lecture 1 Ass. Prof. Eman Farouk  Health Health: is a state of complete physical, mental and social well-being, but not mean the absence of a disease or infirmity. Therefore a health characteristics means well physical and me...

Public health (COMMUNITY MEDICINE) Lecture 1 Ass. Prof. Eman Farouk  Health Health: is a state of complete physical, mental and social well-being, but not mean the absence of a disease or infirmity. Therefore a health characteristics means well physical and mental health, good personality and psychological condition as well as satisfactory economic and living conditions. Factors affecting health Several factors affecting health outcome affecting all stages of faetal formation, before birth (prenatal), at birth (natal) and after birth (postnatal). 1- Prenatal factors: -Genetic factors: related to gene structure of both parents (gene anomaly, gene mutation, presence of genetic diseases in one or of both parents) 2- Natal factors: Care must be taken to minimize the risk of difficult and complicated labor to avoid the exposure of the new born to birth injuries or any hazards 3- Postnatal factors: Health promotion and prevention of health hazards must be fulfilled. Such as adequate nutrition, good housing, satisfactory socioeconomic condition. Medical care for early case- finding and management of morbidity to avoid complications. Mobidity: Is impaired health, which comprise diseases, injury, accidents and disability. Outcome of morbidity: may clear up, or may cause handicapping, and disability, or fatality. Mortality: is a population death. Mortality rate: is the number of deaths in a unit of population within a prescribed time. Public health Public health known as population medicine, preventive medicine or community medicine. Those deal with the study of collective health problems of the community for the promotion of health and prevention of disease. The term preventive medicine is regarded as synonymous with public health, which include : 1- Health promotion: the topmost level of health objectives, which fulfils requirements of physical, mental and social health 2- Prevention of health hazards: includes a- primary prevention: prevent the occurrence of health hazards to which man may be exposed. b- Secondary prevention: prevent the recurrence of the disease to whom previously exposed to a disease e.g rheumatic fever and diarrheal diseases. c- Tertiary prevention: rehabilitation of handicapped individuals to minimize disability. For developing countries, the common community hazards are endemic communicable diseases and nutritional deficiency 3- Control of health hazards: detecting of cases is the base of control for hazards, by health appraisal, the earlier the better. Health appraisal means evaluation and check-up of health status, for the detection of any morbidity, this involves clinical or curative service, screening tests, comprehensive medical examination, and survey studies. 4- Rehabilitation: rehabilitation is needed for handicapped individuals having physical or/mental disability interfering with normal attitude that was may be congenital or acquired  Communicable Diseases Epidemiological studies of communicable diseases include the following: I- Descriptive studies: Observing the distribution of a disease in a community. It depends on collecting data from. a- survey study b- Registered data from health authorities Data should include: 1- Number of cases studied. 2- Segment of people affected. 3- Location and time 4- Age, sex, socioeconomic level, job and material state. II- Analytical study: to show the relation between certain disease and a predisposing factor e.g. cancer and working in asbestos. It may be: 1- Retrospective (in the past ): case of control study a- Case group suffering from certain disease b- Control group: comparable group suffering from the same disease. c- Study of style, diet and work-------ect. 2- Prospective ( followed in future) control or cohort study: a- Study group: individuals exposed to a risky factor e.g. smoking. b- Control group: comparable group but not exposed to the same risk. It is more tedious, but more accurate. III- Experimental studies: also two groups ( study and control ) to show the effect of new drug or vaccine. Results of the studies are expressed as: Incidence of disease in a study group Relative risk=--------------------------------- incidence of disease in control group - prevalence rate of a disease = total number of infected persons (indicate severity of a disease) Number of infected persons X 100 Incidence rate of a disease =-------------------------------- Population risk Epidemiology of communicable diseases: Terminology: Epidemiology: Is the science of epidemics and explosive outbreaks. It is a study of all factors connected to incidence and spread of a disease. Etiology: Causative agent of a communicable disease or infectious disease: A disease caused by specific infectious agent ( transmissible) that could be transmitted by direct or indirect contact from human, animal or insect to human. Infection: Establishment of a relationship between a host and a parasite, may result in disease and /or immunity. Infestation: Development and reproduction of an arthropod on the surface of the body e. g. lice Epidemic A-Epidemic: An outbreak of a disease in a community i. e. when the No. of cases exceeds that expected e,g. cholera of 1948 in Egypt. Epidemics exist in two forms: a- Common source epidemic: People infected from a common source e.g. water, here the number of cases increases and decreases rapidly. b- Propagated epidemic: Person to person epidemic, where the number of cases increases and decreases slowly. B- Endemic: Habitual presence of a disease in a community e,g. bilharzia in Egypt. C- Pandemic: An epidemic occurring over a wide geographic area, more than one nation over the world e.g. plague in wars. d- Sporadic: Infrequent and scattered cases of a disease in a community. Herd immunity: Immunity of the community. It increase by increasing the number of immune population. Zoonotic infection (zoonosis): An infection, which is, transmitted under natural conditions between vertebrate animals (reservoirs of Infection) and human who is infected by direct contact  with infected animals or by indirect means e.g. brucellosis, plague, rabies, anthrax and bovine T. B. Nosocomial infection: Hospitally acquired infection e.g. Pseudomonas, E. coli , Staphylococcuss aureus……. Occupational infection: Infection associated with certain profession (work), are usually zoonotic e.g. brucellosis, anthax, rabies, for farmers, slaughters and veterinarians; leptospirosis for miners and sewers; and psittacosis for peoples handling birds Ecology of disease: Is a synonymous with epidemiology. It is the the natural history of disease and the interaction of triad; man (host), agent (infectious agent that cause disease), and environment. Concerning the following: a- host factors such as: Age, sex, race, occupation, education, culture and lifestyle. b- Infecting agent is the etiology of disease. It either exogenous or endogenous agents. c- Environment which is the medium where man lives or the external surrounding which may influence health. -It comprises, housing, climate, air sanitation, water supply, wastes disposal (refuse and sewage ), insect-vectors and rodents, ventilation……..  Infection Infection means that a pathogenic infectious agent has invaded the body of man, or animal. -The body then tries to defends itself against the invader. The two opposing forces, infection and the body resistance, come in action and the resultant depends on the magnitude of each force. -In most cases the body defense mechanism succeeds to get rid of infection. -Sometimes, however, the invading agent may cause the specific disease. -The two terms infection and disease should be properly applied. Infection may be: 1- Unapparent Infection (carrier): It may be associated with two important phenomena: -First, the host may become a carrier -Second, it may contribute to his immunity through repeated exposure to subclinical dose of infection (immune). 2- Case, the infected individual becomes a patient and shows manifestation of disease. A disease is the visible evidence of the interaction between the invading organism and the body resistance where the body fails to overcome the invader which gains the upper hand. Factors favoring infection: 1- Sanitation of the environment; sanitation is a feature of civilization and goes hand in hand with community development. 2- Health consciousness of the public; unsound health behavior favors the spread and maintenance of infection where the infected individuals contaminate the environment and the susceptible get infected through their faulty habits. 3- Occupation or profession.  The chain of infectious processes 1- Causative agent. 2- Source or reservoir of infection, harboring the agent. 3- Escape (exit) of the agent from the source. 4- Transmission of the agent to a new host. 5- Entry of agent into the host. 6- Susceptibility of the new host to infection. Source ( reservoir ) of infections This is either from human, animal, non living e.g. soil. I- Human reservoir (carrier) either a-Case: Either clinical or subclinical forms. b-Carrier: Is a person who harbors the microorganism and shed it in absence of clinical disease or symptoms. Classification of carriers: A- According to type: 1- Healthy carrier: A healthy person who distribute the infection to another (Healthy carriers are the most dangerous reservoir for infections). 2- Incubatory carrier: A person who shed the microorganism during the incubation period (specially last days of the incubation period) e.g. mumps, measles, and diphtheria. Infectivity is longer in viral hepatitis, and very long in AIDS. Incubation period: The time interval between the entry of the M.O. and the appearance of the first symptom of a disease. 3- Convalescent carrier: A person who still shed the M.O. during the convalescent period e.g. typhoid, dysentery and whooping cough. Convalescent period: The time between the disappearance of symptoms and disappearance of the M.O. from the host. The convalescent carrier is thus clinically cured, but not bacteriologically free. B-According to portal of exit: 1-Respiratory carrier: Shed of M.O. from the upper respiratory tract ( Throat, nose, and nasopharynx) through the mouth and nose e.g. influenza. 2-Fecal (intestinal ) carrier: e.g. typhoid, dysentery, cholera. 3-Blood carrier: e.g. hepatitis B, C, AIDS, malaria….. Organisms in blood find exit through: a-biting arthropod-vectors of disease e.g. relapsing fever and epidemic typhus by louse. B-blood transfusion and blood contaminated needles and syringes e.g. AIDS, syphilis. c-maternal-fetal causing congenital infection 4-Urinary or sexual carrier: e.g. typhoid, gonorrhea, syphilis, AIDS, herpes simplex 2… 5- Skin and mucous membrane lesions: - skin discharges of pyogenic and mycotic lesions. - Skin eruption of varicella, herpes zoster , and variola. - Eye discharge of infective conjunctivitis. - Syphilitic lesions of mouth and genitalia. II- Animal Reservoirs: Zoonoses: Certain infectious agents of a few animals are pathogenic to man. This disease which primarily infects animals, and can also infect man by different methods of transmission. Causative Agents of Zoonosis Viral: rabies, encephalitis, rift valley fever, yellow fever, lymphocytic choriomeningitis. Bacterial: brucellosis, salmonellosis, plague, tuberculosis, anthrax, psittacosis, tularaemia, relapsing fever. Reckettsial: Q fever, typhus fever. Protozoal: amoebiasis, blantidiasis, lishmaniasis toxoplasmosis , trypanosomiasis. III- Soil reservoir: e.g. tetanus, gas gangrene, anthrax botulism ( spore forming bacteria ), fungi and moulds which are capable of independent growth and can infect man. N.B: animal and soil reservoirs are very difficult to eradicate. Foci of Infection Some parts of the body may be inhabited by varied organisms, giving forms of infection foci: either from a carrier state or commensally organisms. Commensals are non pathogenic M.O. under normal conditions, they are potential pathogens (become pathogenic) under adverse circumstances Important foci of infection: 1- Upper respiratory tract: a- Respiratory carriers: from *Throat; Streptococcus pyogens, Staph. aureus, poliovirus, diphtheria. * Nose; Staph. aureus, diphtheria b- Commensals of nasopharynx: e.g Streptococcus viridans, Pneumococcus & meningococcus. 2- GIT: a- Fecal carriers: * Intestine: Salmonella, poliovirus, cholera, Hepatitis A * Colon: shigellae * Gall-bladder: typhoid and paratyphoid b- Intestinal commensals: e.g. E. coli, Streptococcus faecalis, lactobacilli. 3- Urinary tract: * Carriers of typhoid and paratyphoid. 4- Vagina: e.g. commensals anaerobic streptococci and lactobacilli. 5- Mouth: e.g. commensals lactobacilli Mode of Transmission of infections: 1- Droplet (respiratory): a- Direct droplets: Spray of saliva and naopharyngeal secretions during sneezing, coughing or talking e.g. Bacteria: Staphylococcus, Streptococcus pneumoniae, diphtheria, meningococcus, bodetella, T.B. Haemophilus influenza, psittacosis, Q fever, Mycoplama pneumonia. Virus: influenza, mumps, measles, rubella, small pox. b- Air borne droplet nuclei: Dried residues of droplets e.g. T.B. Dust: Due to droplets which settle down on floor e.g. T.B. or psittacosis. c- Fomite borne: e.g. towels, handkerchiefs, spoons, cups……ect. d- Milk borne: Milk could transmit some respiratory infections e.g. streptococci. 2- Food and water (intestinal or oral-fecal ): Those are transmitted as follows feces-flies-food-fingers (4 f) N.B. flies transmit trachoma mechanically but not biologically. Bacteria: Typhoid, dysentery, cholera, food poisoning. Virus: Hepatitis A and polio. Parasites: Entamoeba. 3- Arthropod: (transmit biologically) e.g. -Fleas transmit plague and epidemic typhus -Mosquito transmit yellow fever and malaria -Lice transmit epidemic relapsing fever -Tick transmit endemic relapsing fever -Mites transmit rickettsial pox and scrub fever 4- Contact: Direct transfer through kissing or sexual intercourse e.g. infectious mononuclusis. *Sexual contact e.g Bacteria: Gonorrhea, syphilis. Virus: Herpes simplex type II, Molluscum contagiosum and AIDS. 5- Parentral or blood transfusion: e.g. hepatitis B,C, and AIDS. 6- Animal bite: e.g. rabies 7- Transplacental (TORCH): which causes teratogenic effect on fetus, stillbirth or abortion. Bacteria : Syphilis. Virus: AIDS, Hepatitis B & C, rubellan Cytomegalo virus, Herpes simplex. Protozoal:Toxoplasma