Scientific Working Meeting on Occupational Influenza Prevention and Control in Health Care Settings

Meeting Summary Report

Mississauga, Ontario
October 26 – 27, 2006

PDF Version (4,74MB - 175 pages)

Table of Content

• Introduction
• Summary
• Presentations
  • Michael Tapper MD
  • Burleigh Trevor-Deutsch PhD LLB
  • Mark Nicas PhD
  • Jennifer Goy MSc, Chris O’Callaghan DVM PhD, Dick Zoutman MD FRCPC
  • Michael Gardam MD MSc FRCPC
  • Mary Chamberland, MD, MPH
  • Nick Phin MD
  • Carmem Lucia Pessoa da Silva MD
  • Lisa Brosseau ScD CIH
  • Mary Vearncombe MD FRCPC
  • George Astrakianakis PhD OHSAH
  • Liz Bryce MD
• Discussions
  • Ranking influenza-control measures by efficacy
  • Difficulties of ranking infection-control measures by effectiveness
  • Transmission routes
  • Assessing the relative contributions of possible transmission routes
  • Assessing the relative contributions of preventive measures
  • Host and other biological factors
  • Costs
  • The hierarchy of control measures
• Infection prevention and control measures
  • Pharmaceuticals
  • Early identification
  • Environmental controls
  • Hand hygiene
  • Administrative controls
  • Personal protective equipment (PPE)
  • Surgical masks
  • Respirators
• Deciding on prevention methods in the absence of data
• Next step
• Appendices
  • Agenda
  • Planning Committee Administrative staff
  • Presenters and Facilitator
  • List of Participants
  • Presentations Slides
    • Burleigh Trevor-Deutsch PhD LLB
    • Mark Nicas PhD
    • Jennifer Goy MSc, Chris O’Callaghan DVM PhD, Dick Zoutman MD FRCPC
    • Michael Gardam MD MSc FRCPC
    • Mary Chamberland, MD, MPH
    • Nick Phin MD
    • Carmem Lucia Pessoa da Silva MD
    • Lisa Brosseau ScD CIH
    • Mary Vearncombe MD FRCPC
    • George Astrakianakis PhD OHSAH
    • Liz Bryce MD

---

Introduction

Canada has had a pandemic influenza plan for 19 years, and it continues to evolve based on research, evidence and lessons learned. The Canadian Pandemic Influenza Plan for the Health Care Sector was last revised in December 2006 and has made several additions based on new information in regards to avian and pandemic influenza.

The Public Health Agency of Canada (PHAC) has begun a process to better understand the transmission dynamics of influenza and to prevent its transmission in health care settings. This is a multi-step process and one of these steps was to hold a preliminary scientific working meeting.

These processes will involve a wide variety of experts and stakeholders, and will also include consideration of recommendations from other sources such as the World Health Organization, the United Kingdom Health Protection Agency, and the US Centers for Disease Control and Prevention.

The PHAC is working with stakeholders and expert groups on the revision of the Annex F of the Canadian Pandemic Influenza Plan for the Health Sector. This annex has brought a lot of attention among the health care professionals as it addresses the recommendations for infection control and preventions in health care settings.

The Scientific Working meeting on Occupational Influenza Prevention and Control in Health Care setting was held in Mississauga, Ontario, on October 26 & 27 2006, and was hosted by the PHAC.

The goal of this meeting was to present and discuss scientific evidence pertaining to the transmission of influenza in health care settings. The specific objectives of this meeting were:

• To establish an understanding of the modes of transmission of seasonal, avian (human form) and pandemic influenza based on current scientific knowledge; and
• To identify the hierarchy of practices that are key in the prevention of influenza transmission and the relative contribution of prevention practices.

In order to have a broad spectrum of opinions on the subject, the organizing committee invited organizations and individuals from different scientific views and background. Among them were leading Canadian nurses, physicians, microbiologists, virologists, industrial hygienists and occupational health and safety specialists.

Summary

This report summarizes the twelve presentations that were given at the Scientific Working Meeting on Occupational Influenza Prevention and Control in Health care Settings, held on Oct 26 and 27, 2006, and summarizes and paraphrases, without attribution, the discussions that occurred after each presentation and during the meeting's plenary sessions.

The disciplines practiced by the participants covered a broad range, including industrial hygiene, occupational health, infection-control, and public health. There was consensus on some issues and, not surprisingly, disagreement on others.

The main points made at the meeting and on which most participants agreed were:

• Occupational health and infection-control measures can be classed into a hierarchy by effectiveness.
• Engineering and administrative measures are generally more effective than personal protective equipment.
• Scientific evidence is the best foundation for policy-making.
• There is, as yet, no direct evidence for weighing the relative contribution of droplets, droplet nuclei, direct contact, or fomites in the transmission of influenza.
• When evidence is lacking, policy makers should make explicit the reasons, including the non-scientific ones, for their decisions.

Presentations

Michael Tapper MD
Lenox Hill Hospital, New York

Impact Of Influenza On The Health Care System And Health Care Workers: What Can We Learn From The Past?

Dr Tapper gave an overview of Pandemic Influenza outbreaks, and presented data on how these previous pandemics spread in the USA.

One of his key conclusions was that the "numbers affected in any future pandemic will depend on multiple factors, many of which remain unknown, and any estimates must be viewed as provisional."

Burleigh Trevor-Deutsch PhD LLB
Director, Ethics Office, Canadian Institutes of Health Research

Protecting the Health Care Worker: Managing Risk in the Face of Uncertainty

Dr. Trevor-Deutsch defined the role of ethics in determining best practices in health care, explored the relationship between risk and uncertainty, and suggested ways of dealing with uncertainty.

He recommended that one should base policy on science, but that when scientific information is incomplete, one should integrate ethics. Health care workers should work in an optimally safe environment, and should understand and accept that working in a health care setting during an outbreak involves risk that exceeds background. Policy makers should fully and respectfully address health care workers' subjective interpretation of risk. The nature, quality, and magnitude of workplace risk should be communicated clearly, completely, and in a timely manner, and decisionmakers should be accountable for their decisions.

Mark Nicas PhD
School of Public Health, University of California, Berkeley

Of Droplets and Droplet Nuclei

Dr. Nicas described several mathematical models of the mechanics of influenza infection. By plugging various assumptions derived from the literature into these models he made estimates of exposure to and risk of influenza infection.

His results suggest, among other things, that being more than 1 m from a coughing patient does not prevent inhalation exposure, although most exposure is to droplet nuclei, and being near the coughing patient maximizes the intensity of inhalation exposure to both droplet nuclei and inspirable droplets.

His concluding points were:

• An influenza virus that causes a pandemic is likely to be highly infectious, and probably airborne.
• Given this high infectivity, a low concentration of virus in the air can impart a high risk of infection via inhalation.
• The residual infection risk with poorly fitting respirators may be substantial.

Jennifer Goy MSc, Chris O’Callaghan DVM PhD, Dick Zoutman MD FRCPC
Queen’s University

A Review of The Evidence on Aerosolized Influenza Transmission: Implications for Personal Protective Equipment in Health Care Settings

Goy, O'Callaghan, and Zoutman reported on their systematic review of the scientific literature on modes of transmission.

They gave an overview of the modes of transmission (contact, droplet, and aerosol), described the methodology of their review, and presented a detailed critique of the most widely cited and strongly suggestive evidence for aerosolized influenza transmission.

The studies identified in their review provided no proof that influenza is transmitted via the aerosol route. The studies (on mice, ferrets, prisoners, observations of outbreaks in aircraft and TB wards, etc) cited as evidence of such transmission are limited by the inability to rule out competing hypotheses, lack of reproducible findings, and lack of validity. These studies do not constitute scientific evidence and cannot be responsibly used as the basis for decision-making. Moreover, the overall weight of scientific evidence indicates that influenza is spread via the droplet route.

Michael Gardam MD MSc FRCPC
University of Toronto

How is Influenza Transmitted in Humans? A Systematic Review

Dr Gardam's systematic review included much of the same literature on survival of influenza in the environment, on experimental infections in laboratory animals and in humans, and epidemiological studies of outbreaks as that reviewed by the Queen's University team. (This paper is now in press in Lancet Infectious Diseases)He concluded that:

• The literature supports the idea that close contact is required for transmission to occur. Whether this occurs through droplet, contact, or indirect contact is unknown.
• The literature does not support transmission over long distances. Although there is no evidence that long-distance (airborne) transmission occurs, this has not been conclusively ruled out in the current literature. It was further concluded that if this type of transmission occurs, it is rare.
• There are no data in the literature to define the conditions under which influenza might become opportunistically airborne (i.e., during a bronchoscopy).

Mary Chamberland, MD, MPH
Centers for Disease Control and Prevention, USA

Pandemic Influenza Infection Control Guidance: US Update and Perspectives

Dr Chamberland described the background and context for the development of the recently revised interim US guidance. Following publication of the 2005 HHS Pandemic Influenza Plan, there were many comments and inquiries about the use of surgical masks and respirators. To clarify the guidance, existing data on transmission of influenza were reviewed again. No new scientific information was available.

The approach taken in the revised US Guidance, she said, is cautious, and attempts to bridge the gap between the approaches of traditional infection control and those of industrial hygiene. Supply should not drive recommendations, for example, but the guidance acknowledges that masks and respirators are likely to be in short supply.

The revised guidance highlights the paucity of transmission data as well as the need for improved protective equipment. It will be updated as new information becomes available.

Nick Phin MD
Pandemic Influenza Office, Health Protection Agency, UK

Influenza Prevention and Control in Health Care Settings: United Kingdom Perspective

After discussing the definitions and assumptions needed in infection control, Dr Phin looked at the evidence for possible modes of spread. He noted that people draw different conclusions from the same evidence, and thus recommend different modes of containment. He could not find evidence that high levels of respiratory protection played a part in halting an outbreak. Key elements of UK guidelines include segregation (of influenza patients from others), through cohorting, and an emphasis on the use of hand hygiene and surgical masks.

Pre-requisites for success include stockpiling of personal protective equipment (PPE), and conducting simulation exercises. Such exercises are being carried out in the UK in order to identify, amongst other things, practical and logistic issues with the use of PPE 24 hours a day by many workers, and with the layout of wards.

Carmem Lucia Pessoa da Silva MD
World Health Organization, Geneva

Infection Control Strategies in Health Care

Dr Pessoa da Silva discussed World Health Organization (WHO) initiatives in helping prevent and control infections amongst health care workers. WHO guidelines identify engineering controls, such as reducing the concentration of infectious aerosols in the air by improving the quality of ventilation, are among the most effective of possible measures of controlling the risk of infections related to spread of fine aerosols.

For pandemic (humanized) influenza, the WHO recommends using Standard and Droplet Precautions when providing routine care, and using gowns, gloves, goggles, and particulate respirators when engaged in aerosolgenerating medical procedures.

The use of PPE is not a panacea. Hand hygiene, and the promotion of an organizational safety climate, are very important. She reviewed the degree of preparedness around the world. Only few countries, she said, mostly wealthy countries, have defined infection-control recommendations for health care in the pandemic influenza preparedness plans. In many countries, not only are there no plans, but also sanitary conditions are poor. The goal, she said, is gradual, stepwise improvement in all member states.

Lisa Brosseau ScD
CIH School of Public Health, University of Minnesota

Filter Efficiency and Facial Fit of Surgical Masks

Dr. Brosseau discussed the regulation of filter efficiency and fit in the US. The tests used by the National Institute for Occupational Safety and Health (NIOSH) for measuring filtering efficiency are more stringent than those used by the Food and Drug Administration (FDA). The FDA only regulates the sale and marketing of masks, and in doing so does not require evaluation of fit.

Brosseau described the methods and results of her own study to measure filter efficiency and facial fit for representative surgical masks. The efficiency of surgical masks varies widely, she found, and such masks do not pass even minimum requirements for respirator fit. Even when equipped with relatively efficient filters, they allow 10-40% leakage around the faceplate.

Her conclusions, supported by the results of other studies she cited, are that:

• Surgical masks should not be considered respiratory protective devices.
• The FDA should consider a more robust regulatory approach, including the evaluation of fit.

Mary Vearncombe MD
FRCPC Medical Director, Infection Prevention and Control, Sunnybrook Health Sciences Center, Toronto

Infection Prevention and Control Paradigm

Dr Vearncombe reviewed the principles on which infection prevention and control programs are based. The goals of such programs are to protect patients and others in the health care system, including health care providers, and to do so in a cost-effective way. Prevention is always preferable over control.

Persons in the health care environment are protected through a hierarchy of measures:

• primary (e.g., immunization, education)
• secondary (e.g., PPE, post-exposure prophylaxis)
• tertiary (e.g., outbreak control, treatment of infection)

Protection of persons from infection in the health care environment is dependent on the consistent use of Routine Practices by all health care providers for all patients all the time. Routine Practices include hand hygiene, the use of appropriate barriers (i.e., gloves, gowns, facial protection) when a patient activity is likely to result in exposure, safe sharps management and disposal and appropriate accommodation of patients.

Additional precautions are based on the mode of transmission of an infectious agent and are designed to interrupt that transmission. Additional precautions are initiated both on syndromic presentation and on specific etiologic diagnosis. Additional precautions are always used in addition to Routine Practices.

• contact precautions: gown and gloves on entering patient's room or bedspace (e.g. used for gastrointestinal infection)
• droplet precautions: gown, gloves, mask, eye protection when within 1 meter of patient; single room accommodation (e.g. for patients with febrile respiratory infection)
• airborne precautions: single negative-pressure room accommodation, and the use of high-efficiency particulate filtration mask/respirator (e.g. for TB); for some diseases (e.g. measles, varicella) only immune staff may enter the room.

Decisions as to which practices to use should be based on clinical evidence of risk and on evidence of the effectiveness of the intervention. All interventions carry some level of risk, so the benefit of the intervention must be greater than the risk.

Maintaining a healthy workplace is a joint responsibility of workers and administrators.

Health care dollars must be spent on programs of proven effectiveness, otherwise other programs will suffer, both patient health and safety and occupational health and safety programs. Both cost and efficacy are considered by healthcare decision makers. In the real world where resources are scarce, when you choose to do something, you are choosing to not do something else.

George Astrakianakis PhD
OHSAH Occupational Health and Safety Agency for Health Care in BC

Occupational Hygiene Paradigm

The occupational hygiene paradigm differs from the infection prevention and control paradigm mainly in the need for and the assessment of the efficacy of additional respiratory precautions.

The focus of the infection prevention and control paradigm is on 'routine practice' designed to interrupt contact and droplet transmission. It is assumed that the airborne route of transmission plays a minor role, and thus respirators are required only for specialized procedures.

The occupational hygiene paradigm, on the other hand, is concerned with all three modes of transmission (contract, droplet, and airborne). Though the role played by airborne transmission is not clear, it could be substantial based on occupational hygiene principals and practice. Surgical masks offer only minimal protection against airborne particles, because they do not seal or filter well. On the other hand, when worn properly respirators safely filter biological particles just as they filter any other workplace contaminants.

Within the context of the hierarchy of control measures available to prevent exposure, respirators should be worn whenever health care workers are directly caring for influenza patients.

Liz Bryce MD
University of British Columbia/Vancouver Coastal Health

Hierarchy of Practices: Addressing Influenza Transmission

Dr Bryce reviewed the many uncertainties (about, for instance, the concentration and range of particle sizes reaching the airways of recipients, lack of occupational exposure limits for microorganisms) that make it difficult to assess risk to health care workers.

She classified the factors to be considered in analyzing infection-control measures according to whether they act:

• at the source, (e.g., the degree of infectiousness of the virus, microbial load or the clinical status of the infected patient)
• in transmission (e.g., air flow, filtration, range of particle sizes expelled, aerosolizing procedures, etc)
• in the recipient (e.g., immune status, use of personal protective equipment, compliance with hand hygiene)

She listed a large number of possible interventions or measures for controlling the transmission of infection, classifying them by where they act.

• Interventions that act at the source of infection include early identification of possible cases, masking or isolating patients.
• Interventions that interrupt transmission dynamics include engineering control of air flow, pressure, humidity, and temperature.
• Interventions that act within the recipient include prophylaxis, providing appropriate PPE and education on correct donning and doffing of PPE, and hand hygiene.

Of all the interventions or measures for controlling the transmission of infection that are possible or necessary many remain unexplored or under funded, she said, and we should not neglect other interventions at the expense of focusing on PPE. In addition, while we do have some understanding of the factors that influence a healthcare worker's intent to comply with protocols and procedures, the best way(s) to change behavior and improve the safety climate requires further study.