An update on H1N1 activity

1. An update on H1N1 activity Jamaal A. Russell, MPH, MT Senior Epidemiologist Montgomery County DHHS

2. March 2009 • 2 cases of febrile respiratory illness in children in late March • No common exposures, no pig contact • Uneventful recovery • Residents of adjacent counties in southern California • Tested because part of enhanced influenza surveillance • Reported to CDC as possible Novel influenza A virus infections • Swine influenza A (H1N1) virus detected on April 15th,17th at CDC • Both viruses genetically identical • Contain a unique combination of gene segments previously not recognized among swine or human influenza viruses in the US

3. Epidemiology • Earliest reports • – North America • – Travelers, contacts, schools, cities with community • spread •  Efficient person-to-person transmission from start •  Some aspects very different from seasonal influenza • – High levels of summer disease activity in northern • hemisphere • – Severe and fatal disease focused in younger age • groups • – Deaths primarily associated with rapid respiratory • failure

6. Montgomery County ESSENCE & Flu Flu Season 9/2006-4/2007 Flu Season 9/2007-4/2008 Flu Season 9/2008-4/2009 Pandemic H1N1 April 1, 2009- July 30, 2009

7. Epidemiology/SurveillancePercentage 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 novel 2009-H1N1 – 11 SEPT 2009

8. Epidemiology/SurveillanceWeekly Influenza Activity Reported by SLTT’s novel 2009-H1N1 – 5 SEPT 2009

9. Risk Factors for Severe Illness Children younger than 5 years old, and especially children younger than 2 years old Persons aged 65 years or older Pregnant women Persons with certain chronic medical or immunosuppressive conditions Persons younger than 19 years of age who are receiving long-term aspirin therapy

10. Rate per 100,000 Population by Age Group novel 2009-H1N1 – 24 JUL 2009 (n=37,030*) n=4816 n=7434 n=2187 n=513 *Excludes 6,741 cases with missing ages. Rate / 100,000 by Single Year Age Groups: Denominator source: 2008 Census Estimates, U.S. Census Bureau at: http://www.census.gov/popest/national/asrh/files/NC-EST2007-ALLDATA-R-File24.csv

11. Hospitalization Rate per 100,000 Population by Age Group (n=4,738*) novel 2009-H1N1 – 24 JUL 2009 *Hospitalizations with unknown ages are not included (n=273) *Rate / 100,000 by Single Year Age Groups: Denominator source: 2008 Census Estimates, U.S. Census Bureau at: http://www.census.gov/popest/national/asrh/files/NC-EST2007-ALLDATA-R-File24.csv

12. *April 12 – June 30 Distribution by Age Group of Influenza Hospitalized Cases Emerging Infections Program - Pandemic H1N1 -14 JUL 2009

13. Approximately 70% of persons hospitalized from 2009 H1N1 influenza have had a recognized high risk condition (~60% of children and ~ 80% adults) • Influenza-Related Pediatric Deaths MMWR – Sept. 3, 2009: • 67% percent of children who died with 2009 H1N1 influenza had a high-risk medical condition • 4 of 7 children <5 years old who died with 2009 H1N1 influenza did not have a high-risk medical condition • Among children with high-risk medical conditions, >90% had neurodevelopmental conditions • 59% had > 1 neurodevelopmental diagnoses • 41% had a pulmonary problem

14. Montgomery County ILI activity 3/1/09-9/25/09

15. What have we learned? • It’s here! • Younger age groups are more susceptible • Case Fatality Rate (CFR) is the same as seasonal flu • H1N1 is the predominate flu strain in the US • 67% of H1N1-related pediatric deaths had a high risk medical condition

16. Acknowledgments • CDC- Dr. Joseph Bresee • DHMH- EDCP • Montgomery County DHHS • Disease Control • Emergency Preparedness • Immunization

17. ?Questions?

18. Thank you