INFLUENZA DIVISION Update on the Epidemiology and Clinical Features of Novel H1N1 Joseph Bresee, MD Chief, Epidemiology and Prevention Branch Influenza Division, NCIRD Influenza Division, NCIRD Centers for Diseases Control and Prevention July 15, 2009 The contents of this presentation are those of the presenter and do not necessarily reflect the views of CDC Why are so afraid of bird flu? INFLUENZA DIVISION Increased swine influenza detection in humans January 2007 Novel influenza A made a Nationally Notifiable Disease but CSTE part of pandemic preparedness efforts RT-PCR for influenza capabilities developed by public health labs in U.S. Increasing numbers of swine influenza infections in humans being detected from improved surveillance Increasing efforts at states, CDC, and USDA to investigate human cases of swine influenza Triple-Reassortant Swine Influenza A (H1) in Humans in the United States, 20052009 Shinde, et al. N Engl J Med Jun 18;360(25): INFLUENZA DIVISION Overview Background on novel H1N1 pandemic Epidemiologic features Virologic features Current status of epidemic in the US INFLUENZA DIVISION Novel Influenza A (H1N1) Detected March 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 15 th,17 th 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 MMWR INFLUENZA DIVISION Confirmed and Probable Novel H1N1 Cases by Report Date 17 JUN 2009 (N=40,617) April 23 Mexican Cases of Severe Respiratory Illness are Confirmed as Novel H1N1 April 25 First Cases of the Novel Influenza A H1N1 Virus Recognized in Canada April 25 First Cases of the new Influenza A H1N1 Virus Recognized Outside of North America April 29 WHO Raises Pandemic Alert Level to Phase 5 June 11 WHO Declares Phase 6 Level of Pandemic Influenza Alert INFLUENZA DIVISION International Map Pandemic H1N1 10 JUL 2009 Epidemiology/Surveillance Pandemic H1N1 Hospitalizations Reported to CDC Clinical Characteristics as of 19 JUN 2009 (n=268) Data are provisional and will not be officially released by the CDC until 1100 EDT Internal Use Only (FIUO)---For Official Use Only (FOUO) NOT FOR FURTHER DISTRIBUTION -Sensitive But Unclassified (SBU) 14 Epidemiology/Surveillance Pandemic H1N1 Cases Rate per 100,000 Population by Age Group As of 16 JULY 2009 (n=33,112*) *Excludes 7,505 cases with missing ages. Rate / 100,000 by Single Year Age Groups: Denominator source: 2008 Census Estimates, U.S. Census Bureau at: Data are provisional and will not be officially released by the CDC until 1100 EDT Internal Use Only (FIUO)---For Official Use Only (FOUO) NOT FOR FURTHER DISTRIBUTION -Sensitive But Unclassified (SBU) 15 Epidemiology/Surveillance Pandemic H1N1 Hospitalization Rate per 100,000 Population by Age Group (n=4,395*) As of 16 JULY 2009 *Hospitalizations with unknown ages are not included (n=300) *Rate / 100,000 by Single Year Age Groups: Denominator source: 2008 Census Estimates, U.S. Census Bureau at: Data are provisional and will not be officially released by the CDC until 1100 EDT Internal Use Only (FIUO)---For Official Use Only (FOUO) NOT FOR FURTHER DISTRIBUTION -Sensitive But Unclassified (SBU) 16 Epidemiology/Surveillance Pandemic H1N1 Deaths by Age Group 16 JULY 2009 (n=262) States: AZ - 11 CA - 52 CT - 7 FL - 12 GA - 1 HI - 1 IL - 15 IN - 1 MA - 5 MD - 3 MI - 8 MN - 3 MO - 1 NE - 1 NC - 4 NJ - 14 NY- 57 OH - 1 OK - 1 OR - 5 PA - 8 RI - 2 TN - 1 TX - 24 UT - 14 VA - 2 WA - 4 WI % 25% Median age = 42 years 83% >18 years 67% with underlying disease Influenza-Associated Hospitalizations Deaths By Age Group Epidemiology/Surveillance Pandemic H1N1 Hospitalizations Reported to CDC Underlying Conditions as of 19 JUN 2009 (n=268) *Excludes hypertension Pandemic H1N1 Cases by State Rate / 100,000 State Population As of 16 JUL 2009 Data are provisional and will not be officially released by the CDC until 1100 EDT Internal Use Only (FIUO)---For Official Use Only (FOUO) NOT FOR FURTHER DISTRIBUTION -Sensitive But Unclassified (SBU) 20 Epidemiology/Surveillance Incidence* of Hospitalization for Pandemic H1N1 by Age Group and Selected Sites - 16 JULY 2009 (Note Different Scale for NYC) *Denominator: U.S. Census population estimates for July 2008 for all states, 2007 American Community Survey for NYC Hospitalizations with unknown ages are not included Epidemiology/Surveillance Novel H1N1 16 JUL 2009 EDT Percentage of Visits for Influenza-like Illness (ILI) Reported by the US Outpatient Influenza-like Illness Surveillance Network (ILINet), National Summary and Previous Two Seasons There was no week 53 during the and seasons, therefore the week 53 data point for those seasons is an average of weeks 52 and 1. Data are provisional and will not be officially released by the CDC until 1100 EDT Internal Use Only (FIUO)---For Official Use Only (FOUO) NOT FOR FURTHER DISTRIBUTION -Sensitive But Unclassified (SBU) 22 Epidemiology/Surveillance Novel (H1N1) 16 JUL 2009 U.S. WHO/NREVSS Collaborating Laboratories Summary, * Percentage of all positive influenza specimens that are Influenza A (Pandemic H1N1) or Influenza A (unable to subtype) for the week indicated 37%* 55%* 68%* 73%* 81%* 80%* 85%* 76%* 71%* 65%* 62%* Summary of Antiviral Resistance, U.S Influenza viruses Antiviral Seasonal A (H1N1) Seasonal A (H3N2) Seasonal B Pandemic H1N1 Adamantanes SusceptibleResistantNo activityResistant Oseltamivir Resistant Susceptible Zanamivir Susceptible INFLUENZA DIVISION Summary of key points Once emerged, pandemic H1N1 virus spread to all 5 states and globally quickly Some areas more affected than others Expect continued summertime circulation with focal outbreaks Elderly seemingly relatively spared Capable of causing severe disease and death Most severe outcomes among people with underlying heath problems that are associated with high risk of influenza complications Virus remains sensitive to oseltamivir and zanamvir Whats Next Disease likely persists through summer in US, expected surge in fall Severity of Fall epidemic difficult to predict Southern Hemisphere being monitored for subtypes, spread, and severity Vaccine being readied Surveillance continuing