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.