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The next influenza pandemic

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1997 A/H5N1 avian influenza, Hong Kong. 1999 A/H9N2 human ... of H5 Avian Influenza in ... H5N1 avian influenza virus is changing but development into a ... – PowerPoint PPT presentation

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Title: The next influenza pandemic


1
The next influenza pandemic ?
  • Centre for Infections
  • Health Protection Agency
  • London
  • John Watson
  • July 2005

2
Plan
  • Health protection
  • What is an influenza pandemic?
  • Impact of a pandemic
  • Risk of a future pandemic
  • Pandemic plans
  • Potential responses

3
Health Protection Roles
  • To reduce the dangers to health from infections,
    chemical hazards and poisons, radiological and
    other environmental hazards.
  • Preventing harm
  • Preparing for threats
  • Protecting people

4
Health Protection Agency
5
Health Protection Agency Divisions/Centres
  • Communicable Disease Surveillance
  • Specialist and Reference Microbiology
  • Emergency Response Division
  • Business Division
  • Local and Regional Services
  • Chemical and Toxicological Hazards
  • Radiological Hazards
  • National Institute of Biological Standards and
    Control

6
HPA Nationally
FWE Food, Water Environment
7
Functions
  • Advice to Government on health protection
  • Delivery of services to the NHS and other
    agencies
  • Impartial, authoritative information and advice
    to the public and professionals
  • Rapid response to new threats and emergencies
  • Improved knowledge base through research and
    development, education and training

8
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9
  • Influenza or 'flu' is a respiratory illness
    associated with infection by influenza virus.
  • Symptoms frequently include headache, fever,
    cough, sore throat, aching muscles and joints.
  • There is a wide spectrum of severity of illness
    ranging from minor symptoms through to pneumonia
    and death.
  • The influenza virus was first identified in 1933.
  • There are two main types that cause infection
    Influenza A and influenza B. Influenza A usually
    causes a more severe illness than influenza B

10
Pre-requisites for pandemic influenza
  • PAN (all) DEMOS (people) Epidemic that
  • affects all people
  • New influenza A sub-type Haemagglutinin (HA)
  • unrelated to immediate (pre-pandemic)
  • predecessor. Could not have arisen by mutation.
  • Little or no pre-existing population immunity
  • Person to person spread, causing clinically
    apparent disease
  • Spread (rapid) beyond the community in which it
    was first identified

11
Influenza epidemiology - Pandemics
1889-1892 ? A/H2N2 1900 ? A/H3N8 mild
pandemic 1918 A/H1N1 Spanish
influenza 1957 A/H2N2 Asian influenza 1968 A/H3
N2 Hong Kong influenza (1977 A/H1N1 re-emergenc
e) Shortest interval 11 years Longest
interval 39 years Current interval 36 years
12
Geographic spread 1968-69
09/68
01/69
09/68
09/68
07/68
09/68
08/68
06/69
09/68
C.W. Potter, Textbook of Influenza, 1998
13
Mortality in 20th century pandemics
  • 1918-1919 (A/H1N1) Spanish flu
  • USA, 500,000 excess deaths UK 198,000
  • Worldwide Est. 40 million deaths in three
    distinct waves
  • 1957-1958 (A/H2N2) Asian flu
  • USA, 80,000 excess deaths
  • Worldwide Est. 1 million deaths
  • 1968-1970 (A/H3N2) Hong Kong flu
  • UK 30,000 excess deaths (c/f 26,000 in 1989-90)
  • Worldwide Est. 1 million deaths

14
Age specific influenza death rates among females
in England Wales during 1st and 4th quarters of
1918
Death Rate per 1,000
Ministry of Health, GB, 1919
15
Morbidity associated with pandemic influenza
Persons who consult their GP
1968
25-30
Persons infected with symptoms
1918
25
1957
25-30
50
Persons infected without symptoms
16
Impact in the UK
  • Planning assumption
  • 25 ill (50 infected) over one or more waves of
    about 12 weeks
  • Range 10 50 ill

17
Range of excess deaths (EW)
  • CFR Clinical attack rate
  • 10 25 50
  • 0.37 19,300 48,400 96,700
  • 1.0 51,700 129,200 258,400
  • 1.5 77,100 192,700 258,400
  • 2.5 129,200 323,000 645,900
  • Case fatality rate

18
Pandemic warning
19
Influenza epidemiology Pandemic warnings
1976 A/H1N1 swine-like virus, Fort Dix, NJ,
USA 1977 A/H1N1 global re-introduction 1997 A/
H5N1 avian influenza, Hong Kong 1999 A/H9N2
human cases, Hong Kong 2003/04 A/H7N7 human
cases, Netherlands British Columbia 2002/03 SA
RS outbreak, rapid global spread of novel resp.
virus
20
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21
20 February 2003
  • Chicken flu (influenza A H5N1) in Hong Kong
  • Outbreak in a family linked to southern China
  • Two deaths among four ill
  • Two cases confirmed influenza virus infection

22
Influenza epidemiology Pandemic warnings
1976 A/H1N1 swine-like virus, Fort Dix, NJ,
USA 1977 A/H1N1 global re-introduction 1997 A/
H5N1 avian influenza, Hong Kong 1999 A/H9N2
human cases, Hong Kong 2003/04 A/H7N7 human
cases, Netherlands British Columbia 2002/03 SA
RS outbreak, rapid global spread of novel resp.
virus 2003/04 A/H5N1 further human cases, SE
Asia (Thailand, Korea, Vietnam)
23
Outbreaks of H5 Avian Influenza in Asia In the
period January-March 2004 (with first dates of
animal outbreaks reporting)
24
Recent (since June 2004) outbreaks of H5 Avian
Influenza in Asia  and confirmed Human casesAs
of 16 March 2005 (with first dates of animal
outbreaks reporting)
25
Up to 28 June 2005
26
April 2005
27
WHO global influenza preparedness plan, 2005
28
WHO global influenza preparedness plan, 2005
29
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30
H5N1 as a pandemic virus?
  • Genetic changes
  • Virulence in humans
  • Asymptomatic cases
  • Clusters
  • ? Adaptation to humans

31
UK Alert Levels
A pandemic is thought most likely to start
outside the UK, and to become established in
other countries before reaching the UK. For the
UK, four alert levels are described in the DH and
HPA Plans Alert level 1 Cases due to pandemic
virus only outside the UK Alert level 2 New
pandemic virus isolated in the UK (pandemic
imminent in the UK) Alert level 3 Outbreak(s)
due to new pandemic subtype in the UK Alert level
4 Widespread pandemic activity across UK In
terms of specific actions, both plans assume UK
alert levels 1-4 will be triggered within WHO
phase 2.
32
Current UK vigilance
  • International situation
  • Unexplained clusters of severe respiratory
    illness (esp in health care workers)
  • Returning travellers
  • Large numbers
  • Ordinary respiratory infections

33
Algorithm for the management of returning
travellers from south-east Asia presenting with
febrile respiratory illness recognition,
investigation and initial management.
34
DH and HPA influenza pandemic contingency planning
  • Well advanced, but more to go

35
UKHD and HPA plans in context
  • UKHD plan covers all of UK this includes
    Scotland, Wales and Northern Ireland who now have
    separate Health Departments independent of DH
    England.
  • Considered to be the Overarching UK Plan
  • Covers role of DH England as lead government
    department
  • Covers National Health Service (NHS) and wider
    issues such as essential services (Civil
    Emergency Response)
  • Covers specific responsibilities for policy,
    practice and logistics regarding antiviral drugs
    (oseltamivir Tamiflu) and vaccine (when
    supplies available)

36
UKHD and HPA plans in context
  • HPA plan is an operational manual for the HPA
  • Supports the overarching UKHD plan
  • Covers role of each relevant Centre or Division
  • Contains more detailed projections of impact
  • Concentrates on HPA public health roles
  • - surveillance
  • - diagnostics
  • - modelling (and real-time prediction)
  • - communications
  • - and operational support to NHS and DH England

37
Responses
  • Vaccine

38
Vaccine options
  • Develop vaccine once new strain is identified to
    be causing pandemic
  • Specificity
  • Delay
  • Develop vaccine in advance
  • Limited or no protection

39
Responses
  • Vaccine
  • Antivirals

40
A major decision on antivirals
Health Secretary John Reid today announced the
Department of Health is to procure 14.6 million
courses of oseltamivir (Tamiflu), an antiviral
drug, as part of the UK's preparedness for an
influenza pandemic. John Reid said The plan we
are publishing today, together with our
procurement of these antivirals, puts the UK in
the forefront of international preparedness for a
possible flu pandemic.. ..it makes sense to
ensure we in the UK are as prepared as we can be
and have drugs for use against an influenza
pandemic here. That is why I have ordered 14.6
million courses of oseltamivir for delivery over
the next two financial years. This will enable us
to treat one in four of the UK population - the
proportion which the WHO recommends we plan for.
01 March 2005
41
Responses
  • Vaccine
  • Antivirals
  • Infection control (including masks)

42
Responses
  • Vaccine
  • Antivirals
  • Infection control (including masks)
  • Travel

43
Responses
  • Vaccine
  • Antivirals
  • Infection control (including masks)
  • Travel
  • Social distancing measures

44
Impact on working life
  • Employees sick
  • Employees caring for sick
  • Employees reluctant to travel to, or for, work
  • Disruption to national or international trade or
    commerce
  • Disruption to national infrastructure

45
www.hpa.org.uk
46
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47
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48
The next pandemic ?
  • maximum recorded interval between pandemics is
    39 years
  • likely origin will be SE Asia, seasonality
    unknown
  • rapid global spread
  • several epidemic waves first may be milder
    than subsequent ones
  • excess mortality and morbidity difficult to
    predict but may be high
  • overall population clinical attack rate likely
    to be 25-30
  • likely shift from current inter-pandemic
    pattern of disease, towards younger age
  • groups in terms of severity and mortality
  • impact on health services likely to be
    considerable
  • H5N1 avian influenza virus is changing but
    development into a pandemic strain is still not
    certain

49
Antigenic drift and shift
DRIFT random (small) change in antigenic
structure Influenza A and B
A / H3N2
SHIFT non-random substitution of haemagglutinin
(H) or haemagglutinin and neuraminidase (H and
N). Influenza A ONLY
A / H5N1
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