Preventing Infectious Disease Transmission
Thomas P. FullerScD, CIH, MSPH, MBA
Tech Environmental – Massachusetts Nurses Association
Transmission of Disease 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)
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.
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.
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.
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.
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).
SARS and Healthcare Workers
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
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
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.
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"
Dr. Lee Jong-WookWHO Director-General
November 7, 2005
The Next Pandemic?
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)
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.
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.
Industrial Hygiene, defined:
Anticipation* Recognition* Evaluation Control
Evaluation 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 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.
SAS Air Sampler
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 >35C Filtration efficacy determined at 25C
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.
Control of Aerosols
Reduce generation at source, Containment at the source, Reduce survival in the
environment, General exhaust ventilation, Local exhaust ventilation, Ventilation filtration.
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.
Factors Affecting Aerosol Generation
Energy Input Low = large particles High = small particles.
Infectious Units Organisms per unit Volume of original suspension
Persistence – particle size.
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.
Filtration Systems
Reduce contaminates in the air from local or general exhausts,
Variety of efficiencies for aerosols and gases.
Engineering Controls
Facility Design - isolation Ventilation Filtration Chemicals, gases,
irradiative (UV, IR, RF, microwave, heat)
Isolation Security Systems ?
monitor
corridor
Positive Pressure Room Control
Intended usage's:
•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
• greater than 125 cfm airflow differential supply vs exhaust
• sealed room, about 0.5 sq feet leakage•monitoring
•>12 air exchanges per hour
•recirculate air back through filters
•clean to dirty airflow,
•immune compromised patient rooms
•operating rooms
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
•monitoring•>12 air exchanges per hour new or 6 ac/hr renovation•exhaust to outside or HEPA filtered if recirculated
Negative Pressure Room for Airborne Infection Isolation
Intended usage's:+procedure/treatment rooms+bronchoscopy rooms
+autopsy+emergency rooms
•clean to dirty, airflow
Ventilation Controls % outdoor air, ACH Volume, direction, plena, Evaluation
Frequency, acceptance criteria, IAQ, humidity, particulates,
Filtration, Type, efficiency, testing,
maintenance,
HEPA Filter Assembly
HEPA Filter TechnologyBio-Seal Damper – Butterfly type
Bio-Seal Damper – Dish type
Ventilation/Filtration
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
Establishing Baseline Information
Air quality Non viable & viable
particles
Ventilation Air exchanges, filtration &
pressure
Operational Practice Preventative maintenance Housekeeping Visitation
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.
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.
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.
Barrier managementBarrier management
••Solid versus plastic barriers Solid versus plastic barriers
••Short and long term Short and long term
••Framed or taped barriersFramed or taped barriers
••Ceilings and doors as barriersCeilings and doors as barriers
••Smoke and aerosol controlSmoke and aerosol control
••Pressure differential Pressure differential managementmanagement
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!
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).
Contamination Control
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
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,
OSHA’sRespiratory Protection
Standard29 CFR 1910.134
Permissible Practice Written
Program/Procedures Medical Clearance Fit-Testing and Training Maintenance Record Keeping
Respiratory Protection
Surgical Masks are used to protect immunocompromised patients,
Respiratory Particulate Devices (RPD) N95 are recommended for worker protection.
Air-purifying Respirators Nonpowered
Particle-removing Gas-vapor removing Combination particle gas vapor removing.
Nonpowered Air-purifying Respirator
Advantages Small and compact Lightweight Simple construction Doesn’t restrict
mobility Low initial cost
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.
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.
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
Atmosphere Supplying Respirator
Supplied Air Airline
Continuous flow Demand Pressure demand
Hose-Mask With blower Without blower
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.
Multidisciplinary Teams
Infection Control Committee Medical Doctors, Nurses,
Epidemiologists, Administrators, Facilities Management, Risk Management, Industrial Hygiene, Occupational and Environmental Medicine, Central Processing/Product Sterilization.