Download Pandemic Influenza: Medical Counter

Pandemic influenza:
medical counter-measures
Jo Hofmann, MD
Communicable Disease
Epidemiology Section
Washington State
Department of Health
July 2006
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
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
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
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”)
Hemagglutinin
“H”
• Virus subtypes designated by H
and N numbers
 For
example -- H5N1, H3N2
Influenza virus
• Infects people, animals
and/or birds
• Has a simple genetic
structure
• Likes to share genes and
evolves by:
RNA
genes
 Mutation
 Reassortment
Areas with confirmed H5N1 influenza
in poultry and/or wild birds, 2003-06
As of August 2, 2006
Areas with confirmed H5N1influenza in people, 2003-06
As of August 9, 2006
Total cases
241
Total deaths
141
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
Controlling the
spread of influenza
Medical counter-measures
• List is small
 Influenza vaccine
 Antiviral medications
Annual process of development, manufacturing, and
distribution of influenza vaccine: January- May
Annual process of developing, manufacturing and
distribution of influenza vaccine: May-October
Source: Treanor, J. N Engl J Med 2004;351:2037-2040
Problems with vaccine in a pandemic
• Current technology can’t produce
vaccine without knowing virus
structure
 Is H5N1 a future pandemic virus?
• Vaccine unlikely to be available until
months into pandemic
• Federal gov’t will probably control
distribution of limited vaccine
supplies to state and local
government agencies
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
Antivirals – how they work
M2 inhibitors
(amantidine,
rimantidine)
Neuraminidase
inhibitors
(oseltamivir,
zanamivir)
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
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
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
The estimated impact of a
pandemic on the US and Washington State
Moderate (1957/68-like)
Severe (1918-like)
US
Washington
US
Washington
Outpatient
care
23–54 million
.5 –1.1
million
45 million
943,000
Hospital
Care
.5–1.2 million
10-24,000
9.9 million
210,009
ICU care
77–180,000
15–3600
1.5 million
31,500
Deaths
117–270,000
23–5400
1.9 million
40,400
Modern Quarantine
Honey - will you join me
in registering our
whereabouts with the
appropriate government
bureaucracies?
Oh, Jim you
romantic fool – of
course I’ll wear my
CDC Division of
Global Migration
and Quarantine
Electronic Locator
Ring™