1. INFLUENZA DIVISION U.S. Influenza Surveillance Update, 2008-9 Season Joseph Bresee, MD Epidemiology and Prevention Branch, Influenza Division, CDC VRBPAC Meeting Feb 21, 2008 Gaithersburg, MD

2. INFLUENZA DIVISION Summary of 2008-9 influenza season so far Little disease until last few weeks Overall, a mild season so far Predominance of A(H1N1) Predominance of oseltamivir-resistant H1N1 viruses observed and necessitated a change in recommendations for use of antivirals

3. INFLUENZA DIVISION Seasonal Influenza Geographic Spread Virus Monitoring Mortality Outpatient Illness Hospitalizations Antiviral Resistance

4. INFLUENZA DIVISION Weekly Influenza Activity Estimates by State & Territorial Epidemiologists*

5. INFLUENZA DIVISION Seasonal Influenza Geographic Spread Virus Monitoring Mortality Outpatient Illness Hospitalizations Antiviral Resistance

6. INFLUENZA DIVISION Influenza Positive Tests Reported to CDC by U.S. WHO/NREVSS Collaborating Laboratories, National Summary, 2008-09 Since October 1, 6.6% of ~90,000 specimens tested positive for influenza viruses 78% A 22% B of 32% of A viruses subtyped: -88% A (H1) viruses -12% A (H3) viruses

7. INFLUENZA DIVISION Seasonal Influenza Geographic Spread Virus Monitoring Mortality Outpatient Illness Hospitalizations Antiviral Resistance

8. INFLUENZA DIVISION Epidemic Thresh old Seasonal Base line Pneumonia and Influenza Mortality for 122 U.S. Cities Week Ending 02/07/2009 2007200820062005

9. INFLUENZA DIVISION Number of Influenza-Associated Pediatric Deaths by Week of Death: 2005-06 season to present

10. INFLUENZA DIVISION Seasonal Influenza Geographic Spread Virus Monitoring Mortality Outpatient Illness Hospitalizations Antiviral Resistance

11. INFLUENZA DIVISION Percentage of Visits for Influenza-like Illness (ILI) Reported by the US Outpatient Influenza-like Illness Surveillance Network (ILINet), National Summary 2008-09 and Previous Two Seasons

12. INFLUENZA DIVISION Seasonal Influenza Geographic Spread Virus Monitoring Mortality Outpatient Illness Hospitalizations Antiviral Resistance

13. INFLUENZA DIVISION EIP Influenza Laboratory- Confirmed Cumulative Hospitalization Rates for Children Aged 0-4 and 5-17 yrs, 2007-2008 and Previous 2 Seasons September 30 – February 2, 2008

14. INFLUENZA DIVISION Seasonal Influenza Geographic Spread Virus Monitoring Mortality Outpatient Illness Hospitalizations Antiviral Resistance

15. INFLUENZA DIVISION Antiviral Resistance Week 4 (Jan 25-31, 2009) Oseltamivir-resistant influenza A (H1N1) viruses predominate –have been found in 30 states. –No resistance found among H3N2 and B isolates No resistance to zanamivir noted in any virus tested H3N2s remain adamantane-resistant; H1N1s remain largely adamantane- sensitive The results of antiviral resistance testing performed on these viruses are summarized in the table below:

16. INFLUENZA DIVISION Interim Guidance for Use of Antivirals in the Treatment and Prevention of Influenza, 2008-09 Season *Adapted from Health Alert Network Advisory issued December 19, 2008. Available at http://www2a.cdc.gov/HAN/ArchiveSys/ViewMsgV.asp?AlertNum=00279

17. INFLUENZA DIVISION Rationale: Interim Guidance for Use of Antivirals in the Treatment and Prevention of Influenza, 2008-09 Season Early season data indicated that oseltamivir- resistant H1N1 is the most commonly isolated virus thus far –Strain predominance often changes as season progresses Clinicians need to know that oseltamivir alone might not effectively prevent or treat influenza Health Alert Network advisory issued December 19, 2008

18. INFLUENZA DIVISION Interim Guidance for Use of Antivirals in the Treatment and Prevention of Influenza, 2008-09 Season: Key Points Treatment with zanamivir or a combination of oseltamivir and rimantadine* is preferable in some situations –Influenza subtype likely to be H1 or unknown Local influenza surveillance data and laboratory testing can help with physician decision-making regarding the choice of antiviral agents for their patients Oseltamivir-resistant H1N1 strains are antigenically similar or identical to the strains in the vaccine *Amantadine acceptable in place of rimantadine

19. INFLUENZA DIVISION Advisory Committee on Immunization Practices, February 18, 2009 Influenza session Update on season Antiviral resistance update New recommendations vote –All children aged 6 months through 18 years should receive annual influenza vaccination, beginning in 2008 if feasible, but beginning no later than during the 2009-2010 influenza season –Updated influenza vaccine strains –Separate antiviral recommendations from vaccine recommendations

20. INFLUENZA DIVISION Thank you Weekly FluView available at: http://www.cdc.gov/flu/weekly/fluactivity.htm