NURS 236: Human-Microbial Interactions and Epidemiology PDF

NURS 236: Human-microbe interactions and epidemiology Part 1: Principles of epidemiology and disease 1  Learning Objectives 1. Explain the principles of the epidemiology of infectious diseases in human...

NURS 236: Human-microbe interactions and epidemiology Part 1: Principles of epidemiology and disease 1  Learning Objectives 1. Explain the principles of the epidemiology of infectious diseases in human 2  Epidemiology Study of disease progression within a population (includes when and where) Similar to medical detectives – Looking for non-medical factors that contribute to changes in health Not just etiology, risk factors associated with infections Can address with not only with medicine, but societal practices, control of reservoirs, vectors, etc. Early epidemiologists – Snow – Cholera contaminated well – Nightingale – typhus in armies (food, sanitation, disease 3  Epidemiology Descriptive – Acquire all data about the disease being examined Mostly retrospective (after) Cholera after the Haitian earthquake Analytical – Analyze a disease to try to determine etiology Case control – compare groups with and without disease to ID cause or risk factors Cohort – with or without exposure to the disease 4  Epidemiology Experimental – Hypothesis testing Idea of how disease spreads, a factor influencing its spread, or how it can be treated Test by compare a control and experimental group – Control other values 5  Epidemiology: Terms Notifiable diseases – Infections that must be reported to a public health body if they are found http://dsol-smed.phac-aspc.gc.ca/dsol-smed/ndis/list-eng.php (Canada) Morbidity – Incidence of specific notifiable diseases Mortality – Deaths caused by these notifiable diseases 6  Learning objectives (part 2) 2. To list Koch’s postulates 3. To compare communicable and non-communicable disease 4. distinguish terms for the occurrence and severity of disease 5. To recognize the different impacts on the host 7  Koch’s postulates What are the limitations of Koch’s postulates? Fig. 14.3 Tortora et al., 2013 8  Classifying human disease Communicable – Spreads between hosts (humans or animals) Contagious = easily communicable E.g., chickenpox, measles, herpes, typhoid fever Non-communicable – Doesn’t spread between hosts Normal microbiota that only occasionally causes disease (e.g., opportunistic) OR MOs that normally live in the environment but cause disease in humans E.g., Clostridium tetani, Cryptococcus gattii, Naegleria fowleri 9  Classifying human disease: Occurrences Incidence – New infections Prevalence – New and existing infections (more relevant for longer term infections) Fig. 14.4 Tortora et al., 2013 10  Classifying human disease: Frequency Sporadic – Only shows up occasionally – E.g., typhoid fever in the United States Endemic – Always present in a particular environment – E.g., common cold, malaria in certain areas of Mexico Epidemic – Many new infections in an area over a short period of time – E.g., influenza frequently, MRSA in a hospital or STI in a city/region Pandemic – Epidemic disease at a global scale – E.g., AIDS, occasionally influenza (H1N1, 1918) 11  Classifying human disease: Severity/duration Acute – Develops and resolves quickly – E.g., influenza Chronic/persistent – Slower development, but also longer lasting (continues or recurs) – E.g., infectious mononucleosis, tuberculosis, hepatitis B Latent – Inactive period before producing symptoms Fig 13.21 Tortora et al., 2013 – E.g., Shingles (varicella virus) 12  Classifying human disease: Host involvement/impact Local infections – Limited to a small area of the body – E.g., boils, abscesses, pimples Systemic/generalized infections – Throughout body, typically spread by blood or lymph – E.g., measles Primary infection – Initial infection Secondary infection – Infection that arises due to weakening of immune system by primary infection Subclinical/inapparent infection – Asymptomatic carrier of a MO in/on body 13  Discussion question: Of the following pairs of words that describe infections, identify which of the two do you feel would lead to a more severe or dangerous disease and explain why you chose that word. – Communicable vs. non-communicable – Acute vs. chronic vs. latent – Local vs. systemic/generalized 14