Pandemic influenza: medical counter-measures

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Pandemic influenzamedical counter-measures
Jo Hofmann, MDCommunicable Disease Epidemiology
Section Washington State Department of
HealthJuly 2006

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Influenza - overview

• Review the difference between seasonal, avian
  and pandemic influenza
• Update on avian influenza (H5N1) situation in
  Asia, Europe, Middle East and Africa
• Discuss the use of medical interventions to
  control the spread of pandemic influenza

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Seasonal, avian or pandemic?

• Seasonal influenza
• Flu that circulates each winter the virus
  changes a little from year-to-year
• Avian influenza
• A common infection of birds but virus may also
  infect other species
• Pandemic influenza
• A widespread, multi-continental outbreak of
  serious human influenza
• Caused by a new virus adapted to spread quickly
  between people

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How is influenza spread?

• Flu virus infects cells in nose and throat
• Virus can be spread 24 hours before a person is
  ill until 5-7 days later
• Spread by coughing, sneezing and surfaces
  contaminated with flu virus

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Influenza virus subtypes
Neuraminidase N

• Proteins determine characteristics of a virus
• Which species it infects
• How deadly it is to host
• 2 proteins on surface determine virus subtype
• Hemagglutinin (H)
• Neuraminidase (N)
• Virus subtypes designated by H and N numbers
• For example -- H5N1, H3N2

Hemagglutinin H
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Influenza virus

• Infects people, animals and/or birds
• Has a simple genetic structure
• Likes to share genes and evolves by
• Mutation
• Reassortment

RNA genes
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Areas with confirmed H5N1 influenza in poultry
and/or wild birds, 2003-06
As of August 2, 2006
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Areas with confirmed H5N1influenza in people,
2003-06
As of August 9, 2006 Total cases 241 Total
deaths 141
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Avian influenza and pandemics

• All 20th century pandemics were caused by a virus
  closely related to avian influenza

• Genetic fingerprint of the 1918-1919 Spanish
  influenza pandemic virus looks avian-like but
  the actual source of the virus is unknown

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Controlling the spread of influenza
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Medical counter-measures

• List is small
• Influenza vaccine
• Antiviral medications

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(No Transcript)
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Annual process of developing, manufacturing and
distribution of influenza vaccine May-October
Source Treanor, J. N Engl J Med
20043512037-2040
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Problems with vaccine in a pandemic

• Current technology cant produce vaccine without
  knowing virus structure
• Is H5N1 a future pandemic virus?
• Vaccine unlikely to be available until months
  into pandemic
• Federal govt will probably control distribution
  of limited vaccine supplies to state and local
  government agencies

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Influenza antivirals

• Medications to treat or prevent influenza
• M2 inhibitors - amantidine, rimantidine
• First approved in 1976
• No longer recommended due to resistant influenza
  strains
• Neuraminidase inhibitors oseltamivir,
  zanamivir (Tamiflu, Relenza)
• First approved in 1999

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Antivirals how they work
M2 inhibitors (amantidine, rimantidine)
Neuraminidase inhibitors (oseltamivir, zanamivir)
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Neuraminidase inhibitors

• Compared with M2 inhibitors, fewer side effects
  but more
• Can reduce duration of flu symptoms by 24 hours
  if taken within the first 48 hours of illness
• Can reduce chance of getting flu if exposed
• None shown to reduce the complications associated
  with flu
• Seasonal influenza viruses and H5N1 have been
  identified that are resistant to oseltamivir

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Problems with antivirals in a pandemic

• Pandemic virus could be resistant
• Antivirals may not prevent flu complications or
  deaths
• HHS stockpile enough to treat only 25 of the US
  population
• Waiting list for state/local stockpiles orders is
  long
• Current guidelines are for treatment, not
  prevention of influenza

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Summary

• No magic bullets for the pandemic
• We need more research and improved technology for
  vaccine and antiviral production
• We need more information on how well other
  prevention measures work
• A combination of measures will be needed to limit
  a pandemic

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The estimated impact of a pandemic on the US and
Washington State
Moderate (1957/68-like) Moderate (1957/68-like) Severe (1918-like) Severe (1918-like)
  US Washington US Washington
Outpatient care 2354 million .5 1.1 million 45 million 943,000
Hospital Care .51.2 million 10-24,000 9.9 million 210,009
ICU care 77180,000 153600 1.5 million 31,500
Deaths 117270,000 235400 1.9 million 40,400
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Modern Quarantine
Oh, Jim you romantic fool of course Ill wear
my CDC Division of Global Migration and
Quarantine Electronic Locator Ring
Honey - will you join me in registering our
whereabouts with the appropriate government
bureaucracies?