Methods of Epidemiological investigation Epidemiology is the scientific

Methods of Epidemiological investigation

Epidemiology is the scientific process applied to the control of infections in the healthcare setting.

Origin of the term ‘epidemiology’ • epi - ‘on, upon, at, by, near, over, on top of, against, among’ • demos - ‘common people or citizenry’ • ology - ‘the study of’ • epidemiology =‘Study of disease among the population’

Epidemiology is about Populations • Groups of people not individuals • It answers population questions – aetiology of disease – prevention of disease – Extent/distribution of disease (allocation of effort & resources in health facilities and communities)

Relationship between Epidemiology and Clinical Medicine Studies/Assessments Diagnosis Prevention Treatment Evaluation Cure Planning Care

Examples of Epidemiological Studies • Link between smoking and lung cancer Doll & Hill, 1964

Examples of Epidemiological Studies Water fluoridation: • Communities that had low natural water fluoride levels had high levels of dental caries • Communities that had high natural water fluoride levels had low levels of dental caries

Uses of Epidemiology(Gordis, 2000) • Identifies aetiology or causes of disease including the risk factors for the disease. • Determine the extent of the disease in the community • Examines natural history of disease and prognosis of disease • Investigates and controls disease outbreaks

Uses of Epidemiology(Gordis, 2000) • Describes and monitors the population health and the patterns of disease • Evaluates new preventive and therapeutic interventions and modes of health care delivery • Provides information to inform public policy decisions

Key components of epidemiological studies Target Population Study Population/ Sample Exposure to a study factor Exposed Outcome Unexposed

Key components of epidemiological studies • Target population is the population a researcher wants to make generalizations about • Study population is the group a researcher wishes to study (sometimes the same as the target population) • Study sample is a group of subjects chosen for study to represent the study population

Key components of epidemiological studies • Study factor – is a element that is being investigated to see if it is a determinant of a particular health problem – or if it reduces the impact of a particular health problem. – Study factors can include • risk factors for a health problem, • interventions (therapeutic or preventative) to ameliorate a health condition, • diagnostic tests or techniques and • environmental exposures.

• Exposure is contact with or possessing a particular study factor • Exposed group is a group whose members have had contact with or possess a study factor

Key components of epidemiological studies • Unexposed group is a group that has not had contact with a cause of, or possess a characteristic that is a determinant of, a particular health problem. • Outcome is any or all of the possible results that may stem from an exposure or study factor.

• How is Hospital Epidemiology different from Healthcare Epidemiology? • Healthcare Epidemiology extends the practice into the outpatient areas.

History of infection control and hospital epidemiology in the USA • • Pre 1800: Early efforts at wound prophylaxis 1800 -1940: Nightingale, Semmelweis, Lister, Pasteur 1940 -1960: Antibiotic era begins, Staph. aureus nursery outbreaks, hygiene focus 1960 -1970’s: Documenting need for infection control programs, surveillance begins 1980’s: focus on patient care practices, intensive care units, resistant organisms, HIV 1990’s: Hospital Epidemiology = Infection control, quality improvement and economics 2000’s: ? ? Healthcare system epidemiology modified from Mc. Gowan, SHEA/CDC/AHA training course

Why do we need infection control? ? Hospitals and clinics are complex institutions where patients go to have their health problems diagnosed and treated But, hospitals, clinics, and medical/surgical interventions introduce risks that may harm a patient’s health

Consequences of Nosocomial Infections • Additional morbidity • Prolonged hospitalization • Long-term physical, developmental and neurological sequelae • Increased cost of hospitalization • Death

What is healthcare epidemiology? The fundamental roles of healthcare epidemiology are to: – Identify risks – Understand risks – Eliminate or minimize risks

What is the role of healthcare epidemiology? Identify risks to patient’s health • Find nosocomial infections – surveillance • Identify and study risk factors for nosocomial infections – understand epidemiologic principles and methods – understand nosocomial pathogens – what is it about healthcare institutions that increases risk?

What is the role of healthcare epidemiology? Eliminate or minimize risks to a patient’s health • organize care to minimize risk – eliminate risk factors – work around risk factors – develop improved policies and procedures • educate physicians and nurses regarding risks • study risk factors to learn more about them and how to eliminate them

Responsibilities of the Infection Control Program • Surveillance of • Education of nosocomial infections hospital staff on infection control • Outbreak investigation • Develop written policies • Ongoing review of all aseptic, isolation for isolation of patients and sanitation • Develop written policies techniques to reduce risk from • Eliminate wasteful patient care practices or unnecessary • Cooperation with practices occupational health

Areas of interest to a healthcare epidemiologist • Surveillance for nosocomial infection • Patterns of transmission of nosocomial infections • Outbreak investigation • Isolation precautions • Evaluation of exposures • Employee health • Disinfection and sterilization • Hospital engineering and environment – water supply – air filtration • Reviewing policies and procedures for patient care

Organizing for Infection Control • Requires cooperation, understanding and support of hospital administration and medical/surgical/nursing leadership • There is no simple formula: – Every facility is different – Every facility’s problems are different – Every facility’s personnel are different • The facility must develop its own unique program

Organizing for Infection Control • Main elements – Establish policies and regulations to reduce risks • Develop with clinicians (physicians and nurses) – Develop and maintain a program of continuing education for hospital personnel – Use scientific (epidemiologic) methods to study problems and test hypotheses

Disease Transmission To cause disease, a pathogenic organism must: Leave original host Survive in transit Be delivered to a susceptible host Reach a susceptible part of the host Escape host defenses Multiply and cause tissue damage Disease

Routes of Transmission • Contact: Infections spread by direct or indirect contact with patients or the patient-care environment (e. g. , shigellosis, MRSA, C. difficile) • Droplet: Infections spread by large droplets generated by coughs, sneezes, etc. (e. g. , Neisseria meningitidis, pertussis, influenza) • Airborne (droplet nuclei): Infections spread by particles that remain infectious while suspended in the air (TB, measles, varicella, variola)

Precautions to Prevent Transmission of Infectious Agents • Standard Precautions Apply to ALL patients • Transmission-based Precautions Used in addition to Standard Precautions • Contact • Droplet • Airborne http: //www. cdc. gov/ncidod/dhqp/pdf/guidelines/Isolation 2007. pdf

Standard Precautions • Hand hygiene • Respiratory hygiene and cough etiquette • Personal protective equipment (PPE) Based on risk assessment to avoid contact with blood, body fluids, excretions, secretions • Safe injection practices • Environmental control • Patient placement

PPE for Standard Precautions • Gloves – when touching blood, body fluids, secretions, excretions, mucous membranes, nonintact skin, contaminated items • Gowns – during procedures or patient-care activities when anticipating contact with blood, body fluids, secretions, excretions • Mask, eye protection (goggles or face shield) – during procedures or patient care activities likely to generate splashes or sprays

Transmission-based Precautions

Contact Precautions • Patient placement – Single room or cohort with patients with same infection – If neither is possible, ensure patients are separated by at least 3 ft (1 m) *Change PPE and perform hand hygiene between patient contacts regardless of whether one or both are on contact precautions

Contact Precautions PPE Ш Gown and gloves Ш Don upon entry to room Ш Remove and discard before leaving the room Ш Perform hand hygiene after removal • Environmental measures/patient care equipment – Clean patient room daily using a hospital disinfectant, with attention to frequently touched surfaces (bed rails, bedside tables, lavatory surfaces, blood pressure cuff, equipment surfaces). – Use dedicated equipment if possible (e. g. , stethoscopes, bp cuffs)

Droplet Precautions • Patient placement – Single room or cohort with patients with same infection – If neither is possible, ensure patients are separated by at least 3 ft (1 meter) – Surgical mask on patient when outside of patient room – Negative pressure or airborne isolation rooms not required PPE • surgical mask • Don upon entry into room • Eye protection (goggles or face shield) if needed according to standard precautions

Airborne Isolation Airborne infection isolation room (AIIR)* Monitored negative air pressure in relation to corridor 6 -12 air exchanges/hour Air exhausted outside away from people or recirculated by HEPA filter Surgical mask on patient when not in AIIR (limit movement) PPE – filtering facepiece respirator For all personnel inside negative pressure room * Natural ventilation alone or combined with mechanical ventilation may be a practical alternative in some settings. http: //www. who. int/csr/resources/publications/AI_Inf_Control_Guide_10 May 2007. pdf

TYPES OF NOSOCOMIAL INFECTION BY SITE 1. 2. 3. 4. Urinary tract infections (UTI) Surgical wound infections (SWI) Lower respiratory infections (LRI) Blood stream infections (BSI)

EPIDEMIOLOGICAL INTERACTION Intrinsic host susceptibility Age, Poor nutritional status, Co morbidity, severity of underlying disease Agent factors varieties of organisms Institutional and human Reservoirs & their virulence Environmental factors hospital location, diagn procedures, immunosuppressive, chemotherapy, antibiotics, med & surgical devices, exposure to infected patients or health workers, asymptomatic carriers

MODES OF TRANSMISSION A) BY CONTACT 1) Direct - between Patients and between patient care personnel 2) Indirect - contaminated inanimate objects in environment (Endoscopes etc) 3) Droplet infections by large aerosols B) THRO COMMON VEHICE like Food, Blood & blood products, Diagnostic reagents, Medications C) AIRBORNE e. g. legionellosis, aspergillosis D) VECTORBORNE – by flies

Why surveillance? • NCI cause of morbidity and mortality • One third may be preventable • Surveillance = key factor – an infection control measure – overview of the burden and distribution of NCI – allocate preventive resources • Surveillance is cost-efficient!!

The surveillance loop Health care system Surveillance centre Reporting Action Analysis, interpretation Event Data Information Feedback, recommendations

Objectives • • • Reducing infection rates Establishing endemic baseline rates Identifying outbreaks Identifying risk factors Persuading medical personnel Evaluate control measures Satisfying regulators Document quality of care Compare hospitals’ NCI rates

Who • All hospitals? • All departments? • All specialties? • Other health institutions?

Surveillance of one or more types of NCI Urinary tract infections Lower respiratory tract infections Surgical site infections Bloodstream infections Conjunctivitis Others…

Targeted surveillance • Special patient population (surgical, medical, paediatric, intensive) • Diagnostic and therapeutic procedures (endoscope, haemodialysis, catheterization, blood transfusion) • Specific pathogens (staphylococcus aureus, MRSA, clostridium difficile, norovirus)

Variables • Administrative data – Id, address, dates of admission, discharge. . • Patient related factors: – Age, sex, severity of underlying disease • Procedures – Surgery – Devices (e. g. catheters) • Treatment, diagnosis – Use of antibiotics

When? • During hospital stay? – Frequency of data collection • After discharge? – When and how?

How? • Two main surveillance methods – incidence – prevalence • Variations within these methods

Methodological issues • Definitions NCI – Cut off 48 or 72 hours? – Criterias from Centers for Disease Control and Prevention (hospital) – Mc. Geer (long-term care facilities) Risk variables • Case finding – Active or passive – By whom? – After discharge? – Prospective or retrospective?

SURVEILLANCE Important means of monitoring HAI Early detection of trends outbreaks 1. Laboratory Based Microbiology Laboratory lists +ve organisms ICN reviews ‘Alert organisms’ reported 2. Ward Based Ward staff monitor patients ICN reviews ICN visits wards