Principles of Disease and Epidemiology

Chapter 14 Principles of illness and Epidemiology Pathology transmittance and Disease 1. Pathology is the scientific poll of sickness concerned with feat (etiology) and manner in which indisposition bursts (pathogenesis) alike concerned with structural and functional budges brought about by sickness and last-place effects on the eubstance 2. Infection invasion or colonisation of the ashes by pathogenic microorganisms 3. Disease when transmittal system results in change in state of health Normal Microbiota 1. Free of microbes in utero, at birth gain lactobacilli in intestine from m some other(prenominal)s vaginal canal, E. oli taken d unmatched victuals and inhabits intestine thru life 2. Ten sentences much bacterial cells than human cells in the body 3. Normal flora traffic pattern microbiota 4. pass(a) microbiota present for a while notwithstanding disappear 5. Distribution of normal flora dependent on physical and chemical factors, defenses of the d rove and mechanic factors Relationship between Normal Flora and Host 1. Microbial uncongeniality aka competitive exclusion normal microbiota ability to protect the host from giantism of harmful microorganisms 2. Normal microbiota and host kick the bucket in symbiosis one is dependent on the other 3.The three types of symbiosis commensalism (one organism benefits, other unaffected), mutualism (both benefit) and parasitism (one harmed and one benefits) 4. Probiotics live microbial refinings applied to or ingested that be intended to exert a beneficial effect Opportunistic Microorganisms 1. E. coli ordinarily harmless but in other parts of the body driveway UTI, pulmonary transmission system systems, meningitis or abscesses. 2. AIDS compromises immune system increases susceptibility to opportunistic infection e. g. Pneumocystis pneumonia The Etiology of Infectious Disease Kochs Postulates 1. Koch grounded that microorganisms feature specific distemper 2. Isolate d microorganisms from diseased animal, grew in pure culture and identified, injected healthy animal, disease reproduced and identical 3. Experimental requirements same pathogen must be present in every case of disease, pathogen must be detached from diseased host and grown in pure culture, pathogen must exertion disease when inoculated into healthy animal, pathogen must be isolated from inoculated animal and shown to be original organism Exceptions to Kochs postulates 1.Unique culture environments modified to establish etiologies of those that cannot be grown on artificial media e. g. vir theatrical roles, syphilis, leprosy 2. Some disease much(prenominal)(prenominal)(prenominal) as tetanus have unequivocal signs and symptoms 3. Some disease whitethorn be provoked by a number of microbes e. g. pneumonia and nephritis 4. Some pathogens cause several diseases e. g. S. pyogenes 5. Certain pathogens only cause disease in domain e. g. HIV Classifying Infectious diseases 1. Ever y disease alters body structures and functions in limited ways ad ar indicated by several kinds of evidences 2.Symptoms changes in body functions 3. Signs objective changes the physician can observe or measure e. g. lesions, swelling, pyrexiaishness and paralysis 4. Syndrome a specific group of signs or symptoms that accomp either a disease 5. Communicable disease any disease that public exposures from one host to another e. g. herpes, chickenpox, measles, typhoid feverishness and TB 6. Contagious diseases Spread easily from host to host e. g. chickenpox 7. Noncommunicable Disease caused by microorganisms that restrict body and only occasionally produce disease or live outside the body and produce disease when introduced e. . tetanus Occurrence of Disease 1. Incidence the number of people in a cosmos who develop a disease during a particular accomplishment of judgment of conviction 2. prevalence number of people in a population who develop a disease at a specific time, regardless of when it first appeared sex long timenarian and new 3. Sporadic disease fall outs only occasionally e. g. typhoid fever 4. Endemic disease constantly present in a population e. g. common cold 5. Epidemic disease numerous people in a given area develop disease n pathetic time e. g. AIDS, STDs 6.Pandemic Epidemic disease that occurs worldwide e. g. avian flu Severity or Duration of Disease 1. Acute disease develops rapidly but only lasts a short time e. g. flu 2. Chronic Disease develops much than slowly and bodys reactions may be less severe but continues or recurs for long periods of time e. g. Mono, TB & hepB 3. Subacute Intermediate between Acute and Chronic e. g. Sclerosing panencephalitis 4. possible Disease causative promoter remains in restless for some time but than becomes active to produce symptoms e. . shingles 5. Herd oppositeness Immunity to disease in most of population Extent of Host social function 1. Local infection mic roorganisms limited to relatively small area e. g. boils 2. general infection Spread without the body by blood or lymph e. g. measles 3. Focal infection local infection enters blood or lymph and spread to other specific body parts where they are wrapped arise f/ teeth, tonsils, sinus 4. Sepsis toxic inflammatory condition arising from spread of microbes from a focus of infection 5.Septicemia blood poisoning general infection arising from multiplication of pathogens in blood 6. Bacteremia front of bacteria in blood, Toxemia presence of toxins in blood and viremia presence of virus in blood 7. Primary infection acute infection that causes sign illness 8. Secondary infection caused by an opportunistic pathogen later on primary weakens defenses 9. Subclinical (inapparent) infection is one that does not cause any noticeable illness e. g. Polio & HepA can be carried but never developed Patterns of Disease . Sequence must be reservoir of infection as a source pathogen pa trimonial to susceptible host by radio link or vectors transmission followed by invasion (enters host, multiplies) injures host through pathogenesis 2. Despite these effects, occurance of disease generally depends on resistance Predisposing factors makes body more than susceptible and may alter course of disease 1. Gender Females more UTI, Men more meningitis 2. Genetic background sickle cell against malaria 3. climate and weather respiratory disease increase in winter 4.Others nutrition, age environment, lifestyle, habitat, illness, chemo, emotions. Development of Disease 1. Incubation stage interval between initial infection and first mild signs and symptoms, time depends on virulence, number of microorganisms, and resistance 2. Prodromal period characterized by appearance of the first mild signs and symptoms 3. Period of illness disease at its height and all signs and symptoms apparent, PT dies during this period if not overcome 4. Period of Decline signs and sympto ms subside- vulnerable to secondary infection 5.Period of convalescence body returns to its pre-diseased state and health is restored The Spread of Infection Reservoirs of Infection 1. Reservoir of Infection A continual source of infection- may be human animal or nonliving 2. Human reservoirs Many people harbor pathogens and transmit them Carriers are living reservoirs and harbor the disease with or without signs or symptoms Can carry disease during latent phases such as incubation or convalescent play important reference in spread of AIDS, typhoid fever, diphtheria, hep, gonorrhea, and streptococcal infections 3.Animal Reservoirs Wild or domestic Zoonosis are diseases that occur in wild but can be transmitted to humans e. g. Rabies, Lyme disease Can occur through contact of animal, its waste, consumption or contamination. 4. Nonliving Reservoirs Soil and water supply Soil e. g. Ringworm, Botulism and Tetanus, Water e. g. usually contamination related, cholera , typho id fever Transmission of Disease 1. Contact spread od an agent of disease by direct contact, indirect contact or droplet transmission a. operate Contact touching kissing, intercourse, Any close physical contact e. . STDs, AIDS, cold, influenza, staph, Hep A, measles and so forth b. Indirect Contact occurs when agent of disease is transmitted from reservoir to host by means of nonliving object fomite is a object involved in spread of infection e. g. tissues, bedding, syringes etc. c. Droplet Transmission microbes are spread in droplet nuclei that travel short maintain Sneezing, coughing, talking not considered airborne e. g. flu, pneumonia and pertussis 2. Vehicle Transmission transmission of disease by a medium, such as water diet or air and do drugss blood IV and body fluids d.Waterborne begrime water, cholera leptospirosis e. Foodborne transported through undercooked, poorly kept or unsanitary food such as tapeworm f. Airborne droplet nuclei in make clean that tra vels more than 1 meter measles virus and TB bacteria as well as some spores can be carried in dust and cause disease coccidiodomyosis 3. Vectors animals that carry disease from one host to another g. Mechanical Transmission passive transport on insects feet or body part houseflies transfer from feces to food h.Biological transmission active process and more complex arthropod bites give person pathogens reproduce in vector increase causes more possibility of transmit. If arthropod vomits or defecates while harsh host, can transfer from gut. Often parasites, also entangles Lyme disease, plague, Malaria etc. Nosocomial (Hospital Acquired) Infections 1. A nosocomial infection is any infection that is acquired during the course of stay in a hospital, nursing home or other healthcare quickness 2. About 5 15% of all hospitalized patients will acquire this 3. moderate from combination of weakened host, chain of transmission in hospital and handiness of microorganisms in hospit al. Microorganisms in the Hospital 1. Often normal flora are a problem when introduced to body in catheters and surgical procedures 2. Major problems include coagulase negative staph, S. aureus, E. coli, Enterococcus, P. aeruginosa, Enterobacter, K. pnuemoniae, Candida albicans 3. Most frequent are opportunistic gram negative, drug resistant Compromised Host 1. Resistance impaired by disease, therapy and burns. 2. Two principals disconnected skin/Mucous membranes and suppressed immunity . Broken skin and mucose membranes disable first line of defense 4. Invasive devices also cause problems 5. Adverse effects to B and T Cells compromise host bowed stringed instrument of Transmission 1. Direct transmission from staff member to patient and among patients 2. Fomites such as catheters, syringes and respiratory devices Control of Nosocomial Infections 1. Aseptic techniques can hold Hand washing most important 2. Hospital infection tone down staff members are responsible for over seeing proper cleaning, storage and handling of equipment and supplies emergent Infectious Diseases . EIDs are new or changing, increasing of late and showing future increase. 2. Number of factors contribute to emergence including new strains which may result from genetic recombination (E. coli), a new serovar resulting from changes or evolution (Vibrio cholerea) , use of antibiotics and pesticide to cause resistance, changes in weather patterns (Hantavirus), modern transportation (West Nile), Ecological changes from inseparable disasters construction or wars, animal control measures (kill deer predators, more deer, more Lyme disease and failures in public health measures. . CDC priorities (1) Detect investigate and supervise pathogens and disease (2) Expand basic and applied research on bionomic and environmental factors microbial changes and host interaction (3) Enhance public breeding (4) Establish plans to monitor and control worldwide Epidemiology 1. The science of epidemi ology is the study of transmission incidence and frequency of disease 2.Modern epidemiology began in mid-1800s with the works of Snow, Semmelweis and nightingale 3. Descriptive Epidemiology data about infected people is collected and analyze includes info about person place and period 4. Analytical epidemiology analyzes disease to determine probable cause (case control method) a group of infected people is compared with an uninfected group or (Cohort Method) people in contact with an agent vs. hose not in contact with the same agent 5. Experimental Epidemiology controlled experiments designed to test hypothesis are performed e. g. placebo studying 6. slickness reporting provides data on incidence and prevalence to local, state and case health officials 7. The CDC is the main source of epidemiologic information in the US 8. The CDC publishes the Morbidity and Mortality weekly report to provide info on incidence and deaths.