23 - Inf Control lecture copy.pdf

Infection Prevention & Control (IPAC) & Epidemiology of Infectious Diseases MICI 1100 Ian Davis MD FRCPC Mar 18, 2022  Global Objectives Review the history of Infection Control and basic epidemiology Understand t...

Infection Prevention & Control (IPAC) & Epidemiology of Infectious Diseases MICI 1100 Ian Davis MD FRCPC Mar 18, 2022  Global Objectives Review the history of Infection Control and basic epidemiology Understand the rational for infection prevention and control Be aware of some of the important infections seen in the health care setting Understand the practices to prevent Infection  Brief History of Epidemiology John Snow (1815-1858) – pioneer of Anaesthesia and Epidemiology – Broad Street pump cholera outbreak Soho, London (1854) – 700 deaths linked to contaminate pump – commercial water intake on River Thames linked to illness Broad Street Pump Brief History of Epidemiology Maternal Mortality Rates Puerperal fever 1st and 2nd obstetrics clinics, (General Hospital of Vienna) 8 10 12 14 16 18 Intervention May 15, 1847 Maternal Mortality First Second 4 6 2 0 1841 1842 1843 1844 1845 1846 1847 1848 1849 1850 Semmelweis IP, 1861  Epidemiology of Infectious Diseases? Hundreds of important microorganisms Variety of clinical manifestations – symptomatic vs asymptomatic infection – cancer-related Variety of time courses – acute, subacute, chronic – acute ➔ chronic) Different routes of transmission Different control methods Epidemiologic Triad of Disease Host Disease Agent Environment Chain of Infection Transmission Agent Mode of Transmission  Agent = Pathogen First component in the chain of infection Important characteristics of agent: – Ability to multiply – Ability to withstand environmental stress e.g. temperature, humidity, pH Agent – +/- Nonhuman host reservoirs Epidemiologically important if: – Transmitted (directly/indirectly) – Causes infection Mode of Transmission – Produces clinical disease  Agent Characteristics Infectivity: ability to enter, survive, and multiply within the host # infected = # exposed Pathogenicity: extent to which overt disease is produced in an infected population Agent # with clinical disease = # infected persons Virulence: serious disease-producing potential # serious cases = # with clinical disease Mode of Transmission  Ranking of Infection by Infectivity, Pathogenicity, and Virulence (Nelson & Williams) Grade Infectivity Pathogenicity Virulence High Smallpox Smallpox Smallpox Measles Measles TB Chickenpox Chickenpox Leprosy Rabies Rabies Common cold Intermediate MumpsCOVID-19 Rubella Common cold Rubella Mumps Poliomyelitis Measles Low TB TB Measles Poliomyelitis Chickenpox Very Low Leprosy Leprosy Rubella Common Cold  Agent Reservoir Place where agent lives +/- replicates Mode of Transmission – eg. animal, environment/water, food Must be able to exit reservoir and enter susceptible host via portal of entry – examples: mosquito transmitting malaria contaminated ICU sink (Pseudomonas) incompletely sterilized equipment (MDR-GNR – Klebsiella) Clostridium difficile spores in the environment 5 Modes of Transmission Contact (direct or indirect) – most healthcare associated transmission – e.g. MRSA, Clostridium difficile Droplet: – large respiratory droplets propelled over a short distance (< 2 m) – e.g. Influenza, COVID-19 Common vehicle – from contaminated instruments / products Agent – eg. HIV/HCV contaminated blood products Airborne: – Small droplets (