yellow fever in senegal: strategies for control
DESCRIPTION
Yellow Fever in Senegal: Strategies for Control. Nicholas Eriksson, Heather Lynch, Brendan O’Fallon, Katharine Preedy. Advisor: Simon Levin. http://www.fnai.org/ARROW/almanac/history/history_regional_timeline.cfm. World Health Organization: Communicable Diseases Epidemiological Report (2003). - PowerPoint PPT PresentationTRANSCRIPT
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Yellow Fever in Senegal:Strategies for Control
http://www.fnai.org/ARROW/almanac/history/history_regional_timeline.cfm
Nicholas Eriksson, Heather Lynch, Brendan O’Fallon, Katharine Preedy
Advisor: Simon Levin
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World Health Organization: Communicable Diseases Epidemiological Report (2003)
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Three patch model:Urban, Village, and Forest
U
V
F~ 1,000 individuals with constant rate of infection from forest (monkey) reservoir
~ 10,000 individuals with infection coming from contact with infected individuals from the forest patch
~ 100,000 individuals with infection coming from contact with infected individuals from the village patch
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Urban
Village
Forest
infection from the reservoir
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Num
ber
of In
fect
ed In
divi
dual
s
Num
ber
of
Infe
cted
Ind
ivid
ual
s
Time (days)
Time (days)
~ 2.3 years
rate of infection from reservoir = 0.0001/daytransmission-rate = 0.12/infected individual/dayrecovery rate = 0.10/daycontact probability between forest-village = 0.01/infected individual/daycontact probability between village-urban = 0.01/infected individual/daybirth rate = death rate = 0.0001/day
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Vaccination =
vaccination rate = 2.5e-4 vaccinations/person/day
Fra
ctio
n of
Day
s S
ampl
ed
Number of Infected Individuals
+
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Quarantine 50%
Quarantine 75%
Mea
n U
rban
Infe
cted
Indi
vidu
als
Vaccination Rate
A Comparison of Vaccination Strategies
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Further Work:
• pulsed vaccinations• seasonal fluctuations• mosquito population• mosquito-based control
- spraying
- mosquito nets• less parameter-sensitive models
Summary:
• in this model, the most effective vaccination strategy is in the urban patch
• quarantine can be as effective as vaccination if infected individuals can be properly identified
• vaccination is most effective at the ‘tails’ of the infected distribution, i.e. it eliminates the worst outbreaks
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Eigenvalues of Equilibrium Point of Homogeneous System
Real part of eigenvalues Imaginary part of eigenvalues
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Dominant Eigenvalue
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Vaccination vs. Immigration