Transcript Slide 1

Preventing Infectious Disease
Transmission
Thomas P. Fuller
ScD, CIH, MSPH, MBA
Tech Environmental –
Massachusetts Nurses Association
Transmission of Disease
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Environmental viability,
Exposure route,
Exposure pathway,
Infectious dose,
Incubation,
Organism size/mass/density,
Lethality,
Treatment,
Communicabilty,
Control.
“Control of Hospital Infections-A Practical
Handbook” G. Ayliffe (2000)
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Infection Control Team
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Physicians, ICNs, Management
ICN Activities
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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.
Hospital IC Goals and Measures
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Improve hand hygiene,
Increase environmental cleaning,
Improve equipment cleaning,
Expand contact precautions,
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As measured by,
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Increased soap use,
# of training sessions,
Reduced # of infections, and
Personnel accountability scorecards.
Goals Did NOT Include:
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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.
Healthcare Workers at Risk
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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.
Occupational Threats to Naturally
Occurring Infectious Agents
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Existing
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TB, HIV, hepatitis, measles,
smallpox
Emerging
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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).
SARS and Healthcare Workers
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774 deaths/>8,000 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%.
SARS and Healthcare Workers
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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.
SARS Hospital Management Shortcomings
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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
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Recognition of disease, perception of risk,
understanding disease, inability to prevent
spread.
H5N1 Influenza Pandemic Threat
Current WHO Phase of
Pandemic Alert
"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
The Next Pandemic?
H5N1 Fears
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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)
Industrial Hygiene
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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.
IH Expertise
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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.
Industrial Hygiene, defined:
 Anticipation*
 Recognition*
 Evaluation
 Control
Evaluation
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Historically very little monitoring of
infectious agents is done in U.S.,
Low germ loads led to the feeling that
monitoring didn’t 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.
Air Sample Considerations
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When to sample?
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Commissioning, before occupancy =
baseline,
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Disease outbreak analysis
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Measure all parameters for ventilation
assurance and cleanliness,
To provide comparison data for future
operations,
Measure all parameters with empahsis on
source detection,
Surface and air content for dust and
fungi,
Surveillance
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Pressure is most important,
Air exchanges for purging,
Non viable particles to assess filtration
efficiency,
Viable organisms.
SAS Air Sampler
Interpretation of microbiology
Data
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Rank order analysis
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Qualitative analysis
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Lowest counts in the areas with best filtration
Comparison necessary with outdoor control
Pathogen recovery
Temperature selectivity
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Pathogens grow best at >35C
Filtration efficacy determined at 25C
Surface Monitoring and
Evaluation
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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.
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
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Solid or liquid particles and the gas in
which they are suspended.
Gas
Liquid
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Solid
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Fog, mist, spray, haze.
Dust, fume, smoke.
Solid or Liquid
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Smog, cloud.
Factors Affecting Aerosol
Generation
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Energy Input
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Infectious Units
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Low = large particles
High = small particles.
Organisms per unit
Volume of original suspension
Persistence – particle size.
Aerosol Buildup in
Ventilated Space
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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.
Filtration Systems
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Reduce contaminates in the air from local
or general exhausts,
Variety of efficiencies for aerosols and
gases.
Engineering Controls
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Facility Design - isolation
Ventilation
Filtration
Chemicals, gases, irradiative
(UV, IR, RF, microwave,
heat)
Isolation
Security Systems ?
Positive Pressure Room Control
monitor
corridor
•positive pressure greater supply than exhaust air volume
•pressure differential @ >2.5 Pascal's or 0.01"w.g. ideal
at 0.03”wg or 8 Pascal’s-range from 2.5 to 8.0 Pa
•clean to dirty airflow,
•monitorin
• sealed
room, about 0.5 sq feet leakage
g
Intended usage's:
•immune compromised patient rooms
•recirculate air back through filters
•>12 air exchanges per hour
• greater than 125 cfm airflow differential supply vs exhaust
•operating rooms
Negative Pressure Room for Airborne Infection Isolation
monitor
corridor
•negative pressure greater exhaust than supply air volume
•pressure differential @ 2.5 Pascal's or 0.01"w.g
•sealed room, with about 0.5 sq. feet leakage
•airflow differential >125 cfm
•clean to dirty, airflow
•monitoring
•>12 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
Ventilation Controls
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% outdoor air,
ACH
Volume, direction, plena,
Evaluation
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Frequency, acceptance criteria,
IAQ, humidity, particulates,
Filtration,
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Type, efficiency, testing,
maintenance,
Ventilation/Filtration
Bio-Seal Damper – Butterfly type
HEPA Filter Technology
HEPA Filter
Assembly
Bio-Seal Damper – Dish type
Containment System Monitoring
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Monitors and alarms:
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HEPA Filters
Airflow Velocity
Building Exhaust Fans
Primary Containment
Periodic testing
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Patient isolation rooms
Negative pressure labs
Hospital ventilation and filtration
systems
Establishing Baseline Information
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Air quality
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Ventilation
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Non viable & viable particles
Air exchanges, filtration &
pressure
Operational Practice
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Preventative maintenance
Housekeeping
Visitation
Administrative Controls
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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.
Activities
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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.
Source Management Essential for
Airborne Infectious Disease Control
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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.
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
Contamination Control
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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!
Contamination Control
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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).
Contamination Control
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Sterilization, Disinfection (normal, high level),
Cleaning,
People, surfaces, equipment,
Ensure the methods (procedures) and agents
are appropriate for the needs and don’t
expose patients or workers to undue risks,
Chemicals (EtO, glutaraldehyde,
formaldehyde, hydrogen peroxide,
detergent),
Physical agents (microwave, UV, IR).
Personnel Protective Equipment
Controls
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Laboratories
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Labcoats, closed gowns, gloves, glasses,
goggles, face shields, booties, respirators, air
supplied suits
Patient Care
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Gloves, respirators, air supplied hoods,
gowns, face shields, eyewear,
OSHA’s
Respiratory Protection Standard
29 CFR 1910.134
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Permissible Practice
Written Program/Procedures
Medical Clearance
Fit-Testing and Training
Maintenance
Record Keeping
Respiratory Protection
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Surgical Masks are used
to protect
immunocompromised
patients,
Respiratory Particulate
Devices (RPD) N95 are
recommended for
worker protection.
Air-purifying Respirators
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Nonpowered
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Particle-removing
Gas-vapor removing
Combination particle gas vapor removing.
Nonpowered Air-purifying Respirator
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Advantages
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Small and compact
Lightweight
Simple construction
Doesn’t restrict
mobility
Low initial cost
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Disadvantages
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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.
Powered Air-purifying Respirator
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Types
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Particle-removing
Gas-vapor removing
Combination particle gas vapor removing.
Used when;
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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
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Advantages
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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
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Disadvantages
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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
Atmosphere Supplying Respirator
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Supplied Air
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Airline
Continuous flow
 Demand
 Pressure demand
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Hose-Mask
With blower
 Without blower
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Infection Control
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Preventive strategies to limit the spread
of infectious agents in the health care
setting,
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Patient to patient,
Staff to patient,
Patient to staff, and
Staff to staff.
Extremely important
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JCAHO, patient satisfaction ratings,
financially (stay and treatment durations),
Cost of health care.
Multidisciplinary Teams
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Infection Control Committee
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Medical Doctors, Nurses, Epidemiologists,
Administrators, Facilities Management, Risk
Management, Industrial Hygiene,
Occupational and Environmental Medicine,
Central Processing/Product Sterilization.