Dixie E. Snider, M.D., M.P.H.Senior Advisor, Office of the Director, CDC

Update on Approaches to Understanding Human Influenza Transmission

November 4, 2010

Background for this Meeting

Office of the DirectorOffice of the Associate Director for Science (OADS)

Outline of Presentation

Selected Chronology of Events since April, 2009

High Level Summary of the “State of the Science”

Why the mode or modes of transmission matter to public health

Conclusion

Chronology of Events April, 2009 – Outbreaks of disease caused

by a novel, influenza A (H1N1) strain are detected in Mexico and the United States.

May, 2009 – CDC issues interim recommendations for infection control in healthcare settings. Based primarily on concerns about the severity of disease caused by this new strain, N95 respirators were recommended rather than surgical masks (the standard for seasonal influenza protection).

Chronology of Events (Continued)

June, 2009 – Acting CDC Director orders guidelines for influenza infection control in healthcare settings be reviewed and revised as necessary. External stakeholders are to be engaged.

Early July, 2009 – Informal CDC working group is created to carry out the task. Members represent various CDC components with expertise in the area.

Chronology of Events (Continued) July, 2009 – WG engages external

stakeholders, including healthcare infection control experts, occupational health and safety experts, OSHA, and labor unions representing HCP.

July, 2009 - CDC WG identifies differences of opinion about the use of surgical masks vs. N-95 respirators as a major obstacle to developing consensus guidelines

July, 2009 – IOM is asked by CDC and OSHA to convene a panel to specifically address the respiratory protection issue, without considering “economic and logistical” factors.

Chronology of Events (Continued) September 1, 2009 – IOM panel meets September 3, 2009 – IOM panel issues a

letter report with two recommendations: Recommendation 1: Use Fit-Tested N95 Respirators Recommendation 2: Increase Research on Influenza

Transmission and Personal Respiratory Protection • “The need for research in a number of areas was striking.

Due to the lack of a strong and conclusive evidence base, the committee concluded that determination of the relative contribution of each route of influenza transmission is essential for long-term preparedness planning.”

Chronology of Events (Continued)September 29, 2010 – CDC Director attends

meeting at the White House and emerges with a charge to “fast track” research which would close critical knowledge gaps noted by the IOM.

October, 2009 – Amidst great controversy, CDC issues new interim infection control guidance which continues to recommend N95 respirators, but attempts to address feasibility and logistical issues.

October, 2009 – WHO identifies the mode or modes of influenza transmission as a major knowledge gap.

Chronology of Events (Continued)

October, 2009 – Ten CDC staff members are identified to serve on an “Influenza Research Agenda Steering Committee”. One objective is to create a “fast tack” agenda.

November 2010 – the committee completes its work, presents its proposal to leadership, and receives approval to proceed to implement five projects.

Summary of the “Fast Track” Agenda Study to understand the modes of influenza

transmission Study of the persistence of viable influenza

virus in aerosols A direct comparison of N95 respirators vs.

surgical masks for protection of healthcare personnel

Study of the dispersal of viable airborne influenza viruses and the effect of ultraviolet light

The effect of exclusion policies (e.g., school closures) on influenza transmission

High Level View of“The State of the Science”

The literature on influenza transmission is rather large but is not definitive and often contradictory

There is evidence both for and against each of three modes of transmission, i.e., direct or indirect contact, large droplets, and droplet nuclei (aerosol) transmission

Inappropriate inferences characterize some studies, e.g., close range spread does not necessarily prove large droplet transmission

Study designs often have serious limitations, but optimal designs have not been put forth

Why Does the Mode of Transmissionof Influenza Matter to CDC?

Guideline Development Infection control in healthcare settings Infection control in the workplace Infection control in schools Infection control in public transportation settingsPurchases for the Strategic National

StockpileAssistance to our Federal, national, state,

and local constituencies, e.g. , OSHA, SHEA

Meet Expectations of the PublicMeet Expectations of Executive and

Legislative Branches

Conclusions

Events over the past 18 months have brought attention to the fact that the mode or modes of transmission of influenza are not well understood

Filling this knowledge gap would serve a number of public health purposes

We need your individual advice on the optimal way or ways to fill this knowledge gap

Thank you for Coming!

Questions?