Preventing Infectious Disease Transmission

Thomas P. Fuller ScD, 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"

November 7, 2005

Dr. Lee Jong-Wook WHO Director-General

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 ?

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 g •

Intended usage's: immune compromised patient rooms

•recirculate air back through filters •>12 air exchanges per hour •

operating rooms

• greater than 125 cfm airflow differential supply vs exhaust

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

     % outdoor air, ACH Volume, direction, plena, Evaluation  Frequency, acceptance criteria, IAQ, humidity, particulates, Filtration,  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

 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 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

    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’s Respiratory Protection Standard 29 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.