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Chapter 14 Principles of Disease and Epidemiology Biology 205 Chandler-Gilbert Community College Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Principles of Disease and Epidemiology Pathology: The study of disease Etiology: The study of the cause of a disease Pathogenesis: The development of disease Infection: Colonization of the body by pathogens Disease: An abnormal state in which the body is not functioning normally Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Normal Microbiota and the Host Transient microbiota may be present for days, weeks, or months. Normal microbiota permanently colonize the host. Symbiosis is the relationship between normal microbiota and the host. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.1c Symbiosis In commensalism, one organism is benefited and the other is unaffected. In mutualism, both organisms benefit. In parasitism, one organism is benefited at the expense of the other. Some normal microbiota are opportunistic pathogens. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Normal Microbiota and the Host Locations of normal microbiota on and in the human body. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.1c Normal Microbiota and the Host Microbial antagonism is a competition between microbes. Normal microbiota protect the host by: Occupying niches that pathogens might occupy Producing acids Producing bacteriocins Probiotics are live microbes applied to or ingested into the body, intended to exert a beneficial effect. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Koch’s Postulates Koch's postulates are used to prove the cause of an infectious disease. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.3 (1 of 2) Classifying Infectious Diseases Symptom: A change in body function that is felt by a patient as a result of disease. Sign: A change in a body that can be measured or observed as a result of disease. Syndrome: A specific group of signs and symptoms that accompany a disease. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Classifying Infectious Diseases Communicable disease: A disease that is spread from one host to another. Contagious disease: A disease that is easily spread from one host to another. Noncommunicable disease: A disease that is not transmitted from one host to another. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Occurrence of Disease Incidence: Fraction of a population that contracts a disease during a specific time. Prevalence: Fraction of a population having a specific disease at a given time. Sporadic disease: Disease that occurs occasionally in a population. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Occurrence of Disease Endemic disease: Disease constantly present in a population. Epidemic disease: Disease acquired by many hosts in a given area in a short time. Pandemic disease: Worldwide epidemic. Herd immunity: Immunity in most of a population. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.4 Severity or Duration of a Disease Acute disease: Symptoms develop rapidly. Chronic disease: Disease develops slowly. Subacute disease: Symptoms between acute and chronic. Latent disease: Disease with a period of no symptoms when the patient is inactive. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Extent of Host Involvement Local infection: Pathogens are limited to a small area of the body. Systemic infection: An infection throughout the body. Focal infection: Systemic infection that began as a local infection. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Extent of Host Involvement Bacteremia: Bacteria in the blood. Septicemia: Growth of bacteria in the blood. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Extent of Host Involvement Toxemia: Toxins in the blood. Viremia: Viruses in the blood. Primary infection: Acute infection that causes the initial illness (i.e., Sinus infection). Secondary infection: Opportunistic infection after a primary (predisposing) infection (i.e., Meningitis). Subclinical disease: No noticeable signs or symptoms (inapparent infection). Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Predisposing Factors Make the body more susceptible to disease Short urethra in females Inherited traits such as the sickle-cell gene Climate and weather Fatigue Age Lifestyle Chemotherapy Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings The Stages of a Disease Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.5 Reservoirs of Infection Reservoirs of infection are continual sources of infection. Human — AIDS, gonorrhea Carriers may have inapparent infections or latent diseases. Animal — Rabies, Lyme disease Some zoonoses may be transmitted to humans. Nonliving — Botulism, tetanus Soil Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Disease Contact Direct: Requires close association between infected and susceptible host. Indirect: Spread by fomites. Droplet: Transmission via airborne droplets. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Disease Vehicle: Transmission by an inanimate reservoir (food, water). Vectors: Arthropods, especially fleas, ticks, and mosquitoes. Mechanical: Arthropod carries pathogen on feet (fly). Biological: Pathogen reproduces in vector (Malaria). Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Transmission of Disease Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figures 14.7b, 14.8 Nosocomial (Hospital-Acquired) Infections Are acquired as a result of a hospital stay. 5-15% of all hospital patients acquire nosocomial infections. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figures 14.6b, 14.9 Relative Frequency of Nosocomial Infections Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.5 Common Causes of Nosocomial Infections Percentage of Nosocomial Infections Percentage Resistant to Antibiotics Gram + cocci 51% 29%-89% Gram – rods 30% 3-32% Clostridium difficile 13% Fungi 6% Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Emerging Infectious Diseases Diseases that are new, increasing in incidence, or showing a potential to increase in the near future. Contributing factors Genetic recombination E. coli 0157, Avian influenza (H5N1) Evolution of new strains V. cholerae 0139 Inapproriate use of antibiotics and pesticides Antibiotic resistant strains Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Emerging Infectious Diseases Changes in weather patterns (moisture) Hantavirus Modern Transportation (Hitching a ride) West Nile virus Ecological disaster, war, and expanding human settlement Coccidioidomycosis Animal control measures (Deer) Lyme disease Public Health failure (Lack of water treatment) Diphtheria Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Crossing the Species Barrier Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings UN 13.3 Epidemiology The study of where and when diseases occur Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 14.10 Epidemiology John Snow 1848-1849 Mapped the occurrence of cholera in London Ignaz Semmelweis 1846-1848 Showed that hand washing decreased the incidence of puerperal fever Florence Nightingale 1858 Showed that improved sanitation decreased the incidence of epidemic typhus Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Descriptive Collection and analysis of data Snow regarding occurrence of disease Analytical Comparison of a diseased group Nightingale and a healthy group Experimental Study of a disease using controlled experiments Case reporting Health care workers report specified disease to local, state, and national offices Nationally notifiable Physicians are required to diseases report occurrence Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Semmelweis “AIDS” to “Gonorrhea”; “Pertussis” to “Streptococcal Toxic Shock Syndrome” Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.7 (1 of 2) “Haemophilus influenzae” to “Mumps”; “Streptococcus pneumonaie” to “Yellow Fever” Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Table 14.7 (2 of 2) Centers for Disease Control and Prevention (CDC) Morbidity: Incidence of a specific notifiable disease. Mortality: Deaths from notifiable diseases. Morbidity rate: Number of people affected in relation to the total population in a given time period. Mortality rate: Number of deaths from a disease in relation to the population in a given time. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Centers for Disease Control and Prevention (CDC) Collects and analyzes epidemiological information in the United States. Publishes Morbidity and Mortality Weekly Report (MMWR) www.cdc.gov Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Exam Review Read Chapter 14 Complete the Chapter 14 Quiz Study the Chapter 14 Exam Notes Review the following YouTube video on Malaria for a possible essay question on the Exam. Malaria Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings