Preventing%20Infectious%20Disease%20Transmission

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Preventing Infectious Disease Transmission

• Thomas P. Fuller
• ScD, CIH, MSPH, MBA
• Tech Environmental
• Massachusetts Nurses Association

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Transmission of Disease

• Environmental viability,
• Exposure route,
• Exposure pathway,
• Infectious dose,
• Incubation,
• Organism size/mass/density,
• Lethality,
• Treatment,
• Communicabilty,
• Control.

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Control of Hospital Infections-A Practical
Handbook G. Ayliffe (2000)

• Infection Control Team
• Physicians, ICNs, Management
• ICN Activities
• Surveillance of infections,
• Rapid identification and investigation of
  outbreaks,
• Advice on isolation of patients,
• Development of policies and procedures to control
  the spread of infections,
• Training staff,
• Preparation of annual statistical reports of
  infection rates.

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Hospital IC Goals and Measures

• Improve hand hygiene,
• Increase environmental cleaning,
• Improve equipment cleaning,
• Expand contact precautions,
• As measured by,
• Increased soap use,
• of training sessions,
• Reduced of infections, and
• Personnel accountability scorecards.

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Goals Did NOT Include

• Discussion of worker safety,
• Environmental or personal monitoring for
  infectious agents,
• Evaluation of disinfection or sterilization
  techniques of chemicals,
• Use of engineering controls such as ventilation
  or filtration,
• Selection and use of Personal Protective
  Equipment (PPE),
• The expertise of an Industrial Hygienist.

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Healthcare Workers at Risk

• Injury and illness rate of 10.1
• Greatly under reported due to difficulties in to
  documentation, job classification, poor
  categorization of activities, long latent periods
  HIV, Hepatitis, and large varieties of sources
  and symptoms.

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Occupational Threats to Naturally Occurring
Infectious Agents

• Existing
• TB, HIV, hepatitis, measles, smallpox
• Emerging
• New agents or strains (SARS, H5N1 flu, MRSA),
• New vectors (moving between species),
• New pathways,
• Possibly more infectious,
• Possibly more lethal,
• Super Spreading Events,
• Less understood (vaccines, treatment,
  transmission, viability).

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SARS and Healthcare Workers

• 774 deaths/gt8,000 SARS cases worldwide (9),
• Low infectivity, high severity,
• Many cases hospital acquired (nosocomial),
• 44 deaths/375 cases(12 in Toronto),
• 42 of SARS cases were healthcare workers Toronto
  (57 Vietnam) (Booth),
• Other reported mortality rates range between
  34-52.

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SARS and Healthcare Workers

• Transmission may be via inhalation of aerosols or
  droplets, or mucous membrane contact with fomites
  or body fluids,
• Infection rate was directly proportional to time
  spent in the patients room and illness severity.

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SARS Hospital Management Shortcomings

• Failure to track patient contact history,
• Lack of healthcare worker surveillance,
• Failure/availability of ventilation systems and
  personal protective equipment,
• Failure to track visitor contacts,
• Lack of communications and preparedness
• Recognition of disease, perception of risk,
  understanding disease, inability to prevent
  spread.

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H5N1 Influenza Pandemic Threat
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Current WHO Phase of Pandemic Alert
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"It is only a matter of time before an avian flu
virus -- most likely H5N1 -- acquires the ability
to be transmitted from human to human, sparking
the outbreak of human pandemic influenza"
November 7, 2005

• Dr. Lee Jong-Wook
• WHO Director-General

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The Next Pandemic?
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H5N1 Fears

• Worlds population is immunologically vulnerable,
• A new strain for which there are no residual
  antibodies from
• previous seasonal
• influenza outbreaks,
• An extremely
• virulent disease,
• (52-55 mortality).
• (www.who.int)

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Industrial Hygiene

• Misunderstood and underutilized,
• IC is unaware of IH capabilities,
• Sophisticated IH activities are performed by
  other departments with little understanding or
  knowledge of IH principles,
• Decisions made based on outdated assumptions and
  poor understanding of IH concepts (e.g. aerosol
  physics),
• Difficulty for IH principles an suggestions to be
  understood or accepted.

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IH Expertise

• Aerosol/particle physics,
• Ventilation design/operation,
• Air filtration systems,
• Exposure assessment and control,
• Contamination control/decontamination
  (toxicology),
• Risk assessment,
• Personnel Protective Equipment,
• Respiratory Protection,
• Biological hazards, and
• Air monitoring/sampling and analysis.

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Industrial Hygiene, defined

• Anticipation
• Recognition
• Evaluation
• Control

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Evaluation

• Historically very little monitoring of infectious
  agents is done in U.S.,
• Low germ loads led to the feeling that monitoring
  didnt provide any useful information at such low
  levels,
• As a result few hospitals maintain the equipment
  or expertise in airborne or surface monitoring
  for infectious agents,
• Additionally, not a lot is known about how and
  what to monitor, viability, and what are
  acceptable (safe) concentrations.

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Air Sample Considerations

• When to sample?
• Commissioning, before occupancy baseline,
• Measure all parameters for ventilation assurance
  and cleanliness,
• To provide comparison data for future operations,
• Disease outbreak analysis
• Measure all parameters with empahsis on source
  detection,
• Surface and air content for dust and fungi,
• Surveillance
• Pressure is most important,
• Air exchanges for purging,
• Non viable particles to assess filtration
  efficiency,
• Viable organisms.

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SAS Air Sampler
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Interpretation of microbiology Data

• Rank order analysis
• Lowest counts in the areas with best filtration
• Comparison necessary with outdoor control
• Qualitative analysis
• Pathogen recovery
• Temperature selectivity
• Pathogens grow best at gt35C
• Filtration efficacy determined at 25C

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Surface Monitoring and Evaluation

• Not historically done to a great extent in health
  care,
• Very useful demonstration during the SARS
  outbreak to demonstrate transmission throughout
  the hosptial ,
• cfus per square cm.

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Control of Aerosols

• Reduce generation at source,
• Containment at the source,
• Reduce survival in the environment,
• General exhaust ventilation,
• Local exhaust ventilation,
• Ventilation filtration.

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Aerosols

• Solid or liquid particles and the gas in which
  they are suspended.
• Gas
• Liquid
• Fog, mist, spray, haze.
• Solid
• Dust, fume, smoke.
• Solid or Liquid
• Smog, cloud.

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Factors Affecting Aerosol Generation

• Energy Input
• Low large particles
• High small particles.
• Infectious Units
• Organisms per unit
• Volume of original suspension
• Persistence particle size.

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Aerosol Buildup in Ventilated Space

• 30 air changes per hour required to maintain or
  reduce concentrations,
• Highest concentrations are in work areas,
• Breathing zone is within 3 feet of source.

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Filtration Systems

• Reduce contaminates in the air from local or
  general exhausts,
• Variety of efficiencies for aerosols and gases.

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Engineering Controls

• Facility Design - isolation
• Ventilation
• Filtration
• Chemicals, gases, irradiative (UV, IR, RF,
  microwave, heat)
• Isolation
• Security Systems ?

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Positive Pressure Room Control
monitor
corridor
positive pressure greater supply than exhaust
air volume
pressure differential _at_ gt2.5 Pascal's or
0.01"w.g. ideal at 0.03wg or 8 Pascals-range
from 2.5 to 8.0 Pa
clean to dirty airflow,
Intended usage's
monitoring
immune compromised patient rooms
sealed room, about 0.5 sq feet leakage
operating rooms
recirculate air back through filters
gt12 air exchanges per hour
greater than 125 cfm airflow differential
supply vs exhaust
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Negative Pressure Room for Airborne Infection
Isolation
monitor
corridor
negative pressure greater exhaust than supply
air volume
pressure differential _at_ 2.5 Pascal's or 0.01"w.g
sealed room, with about 0.5 sq. feet leakage
airflow differential gt125 cfm
clean to dirty, airflow
monitoring
gt12 air exchanges per hour new or 6 ac/hr
renovation
exhaust to outside or HEPA filtered if
recirculated
Intended usage's
procedure/treatment rooms
bronchoscopy rooms
autopsy
emergency rooms
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Ventilation Controls

• outdoor air,
• ACH
• Volume, direction, plena,
• Evaluation
• Frequency, acceptance criteria, IAQ, humidity,
  particulates,
• Filtration,
• Type, efficiency, testing, maintenance,

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Ventilation/Filtration
Bio-Seal Damper Butterfly type
HEPA Filter Technology
HEPA Filter Assembly
Bio-Seal Damper Dish type
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Containment System Monitoring

• Monitors and alarms
• HEPA Filters
• Airflow Velocity
• Building Exhaust Fans
• Primary Containment
• Periodic testing
• Patient isolation rooms
• Negative pressure labs
• Hospital ventilation and filtration systems

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Establishing Baseline Information

• Air quality
• Non viable viable particles
• Ventilation
• Air exchanges, filtration pressure
• Operational Practice
• Preventative maintenance
• Housekeeping
• Visitation

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Administrative Controls

• Policies/Plans/Programs/Procedures
• Oversight and Review
• Enforcement
• Access Control/Contact/Transport
• Training (simulated Labs, medical drills)
• Vaccination, patient screening and isolation,
  medical surveillance, prophylaxis and treatment,
• Cleaning, Disinfection, Sterilization.

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Activities

• Continually review infection rates and sources,
• Track and trend infection data,
• Develop programs and procedures,
• Communicate issues and work to develop solutions,
• Monitor systems and correct deficiencies.

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Source Management Essential for Airborne
Infectious Disease Control

• Patient sources need to be recognized and
  isolated,
• Environmental sources need to be managed through
  training and procedural practice,
• Healthcare facilities must be maintained,
• New facility design should facilitate infection
  control measures.

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Barrier management
Solid versus plastic barriers Short and long
term Framed or taped barriers Ceilings and
doors as barriers Smoke and aerosol
control Pressure differential management
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Contamination Control

• Not as well understood in health care as we might
  like to think (health physics, nuclear power),
• Little actual experience of workers with
  real-time monitoring,
• Little actual awareness of how agents are spread
  on surfaces or might physically move about,
• Few measurement methods currently available,
  basically none in real-time!

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Contamination Control

• Consists of making a best guess of where the
  agents are likely to be (get),
• Often there is very little understanding on the
  part of the medical community of the
  environmental viability of known organisms, much
  less unknown ones! (SARS).

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Contamination Control

• Sterilization, Disinfection (normal, high level),
  Cleaning,
• People, surfaces, equipment,
• Ensure the methods (procedures) and agents are
  appropriate for the needs and dont expose
  patients or workers to undue risks,
• Chemicals (EtO, glutaraldehyde, formaldehyde,
  hydrogen peroxide, detergent),
• Physical agents (microwave, UV, IR).

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Personnel Protective Equipment Controls

• Laboratories
• Labcoats, closed gowns, gloves, glasses, goggles,
  face shields, booties, respirators, air supplied
  suits
• Patient Care
• Gloves, respirators, air supplied hoods, gowns,
  face shields, eyewear,

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OSHAsRespiratory Protection Standard29 CFR
1910.134

• Permissible Practice
• Written Program/Procedures
• Medical Clearance
• Fit-Testing and Training
• Maintenance
• Record Keeping

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Respiratory Protection

• Surgical Masks are used to protect
  immunocompromised patients,
• Respiratory Particulate Devices (RPD) N95 are
  recommended for worker protection.

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Air-purifying Respirators

• Nonpowered
• Particle-removing
• Gas-vapor removing
• Combination particle gas vapor removing.

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Nonpowered Air-purifying Respirator

• Disadvantages
• Cannot be used in oxygen deficient atmosphere
• Cannot be used in IDLH atmosphere
• Poor warning properties
• Possible leakage
• Cannot be worn with a beard
• High cost
• High maintenance
• Less comfortable, irritates eyes.

• Advantages
• Small and compact
• Lightweight
• Simple construction
• Doesnt restrict mobility
• Low initial cost

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Powered Air-purifying Respirator

• Types
• Particle-removing
• Gas-vapor removing
• Combination particle gas vapor removing.
• Used when
• the agent is known,
• Air concentrations are known,
• No other hazards are present,
• Sufficient Oxygen
• No chemical hazards
• No radioactive materials.

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Powered air purifying respirator

• Advantages
• No restriction on mobility
• Minimal breathing resistance
• Cooling affect on wearer
• Can be worn for long periods
• Fit tests not required
• Can be worn with beards

• Disadvantages
• Cannot be used in oxygen deficient atmosphere
• Cannot be used in IDLH atmosphere
• Poor warning properties
• Functional limitations, restricts movement
• Discomfort to wearers
• Higher cost and maintenance

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Atmosphere Supplying Respirator

• Supplied Air
• Airline
• Continuous flow
• Demand
• Pressure demand
• Hose-Mask
• With blower
• Without blower

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Infection Control

• Preventive strategies to limit the spread of
  infectious agents in the health care setting,
• Patient to patient,
• Staff to patient,
• Patient to staff, and
• Staff to staff.
• Extremely important
• JCAHO, patient satisfaction ratings, financially
  (stay and treatment durations),
• Cost of health care.

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Multidisciplinary Teams

• Infection Control Committee
• Medical Doctors, Nurses, Epidemiologists,
  Administrators, Facilities Management, Risk
  Management, Industrial Hygiene, Occupational and
  Environmental Medicine, Central
  Processing/Product Sterilization.