Pandemic Influenza: Current Perspectives

1
Update on the 2009 Influenza A(H1N1) Pandemic in
the United States
Mark Simmerman, PhD Chief, Influenza
Section International Emerging Infections
Program Thailand MOPH-US CDC Collaboration
The contents of this presentation are those of
the presenter and do not necessarily reflect the
views of CDC
2
Novel Influenza A (H1N1) Detected

• 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

3
2009 Pandemic Influenza A(H1N1)

• Novel and unique quadruple reassortant with
• Swine influenza virus of North American lineage
• North American avian influenza virus
• One segment of human influenza virus
• Swine influenza virus normally found in Asia and
  Europe
• Not previously detected in swine or humans

4
Next cases detected in Texas

• On April 22, 2009
• 2 additional cases of febrile respiratory illness
  
• Residents of the same county in Texas
• Swine influenza A (H1N1) virus, genetically
  similar to California cases
• Two 16 year-old boys met case definition for
  febrile respiratory illness
• Illness onset 4/10 and 4/14
• Both tested on 4/14
• Go to same school but not family
• No known pig exposure
• Case investigation started

5
Confirmed and Probable pandemic H1N1 Cases by
State as of 27 April 2009
(1)
1
(1)
NYC 28
7 (4)
2
2 (4)
States with confirmed cases
States with probable cases but no confirmed
6
Confirmed and Probable Novel H1N1 Cases by
Report Date as of 24 July 2009
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US Surveillance for Novel H1N1

• No longer getting individual case counts
• As of August 27, 2009 there were
• Sex 50 male/female
• Median age
• All cases - 12 years (as of July 24)
• Hospitalized - 19 years (as of July 24)
• Died - 42 years (as of July 16)
• As of September 1st, all counts reset to zero.
  Now reporting all influenza deaths (not just
  pandemic H1N1)
• Aggregate weekly counts by age group for
  hospitalizations and deaths

8
Clinical Characteristics of Hospitalized
Cases(case series of 268)
9
Pandemic H1N1 Cases Rate per 100,000 Population
by Age GroupAs of 09 JULY 2009 (n35,860)
n17829
n3621
n5774
n1673
n382
Excludes 1,386 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/fi
les/NC-EST2007-ALLDATA-R-File24.csv
10
Hospitalization Rate per 100,000 Population by
Age Group (n6,124)
Hospitalizations with unknown ages are not
included (n382) 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
Death Rate per 100,000 Population by Age Group
Deaths with unknown ages are not included (n4)
Rate / 100,000 by Single Year Age Groups
Denominator source 2008 Census Estimates, U.S.
Census Bureau at http//www.census.gov/popest/na
tional/asrh/files/NC-EST2007-ALLDATA-R-File24.csv
12
Seasonal Influenza-Associated Hospitalizations
Deaths By Age Group
Thompson WW, JAMA, 2004
13
Pandemic H1N1 Hospitalizations andUnderlying
Conditions (n268)
Excludes hypertension
14
Pandemic H1N1 Cases by StateRate / 100,000 State
Population
15
Influenza Positive Tests Reported to CDC by U.S.
WHO/NREVSS Laboratories, 2008-09
16
Percentage of Visits for Influenza-like Illness
(ILI) Reported by the US Outpatient
Influenza-like Illness Surveillance Network
(ILINet)
17
Weekly Influenza Activity by State (Week of Sept
19)
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Summary of Antiviral Resistance, U.S. 2008-09
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Antiviral Treatment Recommendations

• Priority Hospitalized Patients with suspected or
  confirmed pandemic H1N1 virus infection
• Treatment recommended with Oseltamivir or
  Zanamivir
• Treat patients as soon as possible (duration 5
  days)
• Outpatients with suspected or confirmed pandemic
  H1N1 infection at high risk for complications
• Persons with chronic pulmonary, cardiac, renal,
  hepatic, metabolic, hematological disorders
  immunosuppression, pregnant women, children lt5
  years adults 65 years
• Treatment recommended with Oseltamivir or
  Zanamivir
• Treat patients as soon as possible (duration 5
  days)

http//www.cdc.gov/h1n1flu/recommendations.htm
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Influenza A (H1N1) 2009 Monovalent
Vaccine(Advisory Committee on Immunization
Practices)

• Guiding principle - vaccinate as many persons as
  possible as quickly as possible
• Five initial target groups (159 million)
• Pregnant women
• Persons who live with or provide care for infants
  aged lt6 months
• Health-care and emergency medical services
  personnel
• Children and young adults aged 6 months--24 years
• Persons aged 25--64 years who have medical
  conditions that put them at higher risk for
  influenza-related complications
• Guidance on use of vaccine in other adult
  population groups as vaccine availability
  increases
• US FDA announced 1 dose is sufficient in persons
  gt9 years
• 2 doses required for 6 months to 9 years of age
• US President- 10 of US vaccines will be donated
  to developing countries

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Summary

• Pandemic H1N1 virus quickly spread nationally,
  globally
• Some states, cities more affected than others
• Summertime circulation with focal outbreaks
  observed
• Elderly relatively spared
• Capable of causing severe disease and death
• Most severe outcomes in people with underlying
  heath problems
• Virus remains sensitive to oseltamivir and
  zanamvir
• Rapid and early fall rise in ILI visits detected
• Pneumonia admissions currently at expected levels
• Monovalent vaccination available beginning
  October

22
Priority Issues Requiring Close Monitoring

• Genetic mutations that confer resistance to
  Zanamivir
• Outbreaks of Oseltamivir resistant infections
• Change in pathogenicity of H1N1 pandemic virus
• Vaccine adverse events

23
Thank you

• Image by Karsten Schneider/Science Photo Library