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Pandemic preparedness: What can epidemiological modelling offer policy?

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From today to emergence of a novel ... Headache, sore throat, chills, fever, myalgia, anorexia, ... bird to human by inhaling dried aerosolised faeces ... – PowerPoint PPT presentation

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Title: Pandemic preparedness: What can epidemiological modelling offer policy?


1
Pandemic preparednessWhat can epidemiological
modelling offer policy?
  • Nim Arinaminpathy
  • Department of Zoology
  • University of Oxford

2
Talk plan
  • Influenza a background
  • From today to emergence of a novel influenza
    virus
  • Antiviral drugs for control of pandemic influenza

3
Influenza
  • RNA virus
  • Clinical manifestations
  • Headache, sore throat, chills, fever,
  • myalgia, anorexia, malaise
  • Transmission
  • By contact with respiratory droplets,
  • generated by coughing or sneezing
  • Infectiousness
  • can start a day before symptoms and continue for
    3 5 days after symptoms developing in adults

4
The seasonal influenza burden
  • Disease
  • 5 15 of population affected with upper
    respiratory tract infections in annual flu
    season
  • Estimated 3-4,000 annual deaths in UK caused by
    influenza infection (mainly elderly and
    immunocompromised)
  • The Economy
  • Europe flu accounts for 10 of sick leave
  • Costs US estimated 90bn a year

5
Influenza family tree
Orthomyxoviridae

Influenza
From http//www.abc.net.au/health
A
B
C
Type

H1N1
Subtype
H3N2
6
Pandemic and seasonal influenza
Taken from www.en.influenza.pl
7
Social and economic disruption
8
Social and economic disruption
9
H5N1 Future pandemic?
  • Wild bird reservoir ? Poultry ? Humans
  • Transmitted from bird to human by inhaling dried
    aerosolised faeces
  • First major outbreak in 1997, Hong Kong
  • Resurgence in 2003 has seen virus established in
    poultry in South-East Asia
  • So far human-to-human spread is non-existent or
    very limited
  • 387 human cases, 245 deaths to date
  • Wide geographical spread, from S.E.Asia (inc.
    Indonesia, Viet Nam) to Africa (Nigeria, Egypt)
  • However, H7N7 and N9N2 are also pandemic
    candidates

10
Evolution and emergence of pandemic influenza
  • Each human case is an opportunity for an avian
    virus to adapt for human transmission

11
Antiviral drugs for pandemic control
  • No vaccine for at least first 6 months
  • Oseltamivir (Tamiflu) is main antiviral drug of
    choice
  • UK stockpile
  • Currently enough for 25 of population
  • Drugs intended mainly for treatment, not
    prophylaxis
  • For all clinical cases
  • How best to minimise epidemic size and impact
    with a limited stockpile?

12
A simple compartmental model
?T
a?
IT
RT
S
?N
(1-a)?
IN
RN
13
A simple compartmental model
?T
a?
IT
RT
S
?N
(1-a)?
IN
RN
14
1957 Asian Flu pandemic
30/11/57
22/02/58
15
1957 Asian Flu pandemic
16
1957 Asian Flu pandemic
17
1957 Asian Flu pandemic
CFR 0.16 R0 1.65
25 stockpile exhausted
18
How many drugs are needed?
Secondary effect of mass antiviral treatment is
to reduce the spread of infection in the
community Its strength depends on drug
efficacy and disease transmissibility
19
Antiviral programmes
  • By shortening infectious period and reducing
    infectiousness, antiviral drugs can influence the
    course of infection
  • Broadening and delaying epidemic peak
  • Reducing numbers of cases
  • If there is a risk-group for whom the drug has
    little protective effect, the stockpile is better
    deployed in the general population.
  • Priority shifts to protection from infection
    rather than from illness.

20
The social element
  • Potential wastage of drugs on the worried well
  • Personal stockpiles
  • Non-compliance with treatment regime may lead to
    drug resistance
  • Pressing ethical questions, eg distributive
    justice

21
Conclusions
  • Mathematical models can offer valuable insights
    into disease control
  • Transmission dynamics are often fundamental to
    epidemic outcomes and effects of interventions
  • sometimes offering counterintuitive results!
  • However models always entail simplifications,
    often about human behaviour (important factors)
  • Effective pandemic preparedness could involve a
    synergy between such models and the social
    sciences
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