yellow fever in senegal: strategies for control nicholas eriksson, heather lynch,
DESCRIPTION
World Health Organization: Communicable Diseases Epidemiological Report (2003)TRANSCRIPT
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
World Health Organization: Communicable Diseases Epidemiological Report (2003)
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
Urban
Village
Forest
infection from the reservoir
Num
ber o
f Inf
ecte
d In
divi
dual
s
Num
ber o
f Inf
ecte
d In
divi
dual
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
Vaccination =
vaccination rate = 2.5e-4 vaccinations/person/day
Frac
tion
of D
ays
Sam
pled
Number of Infected Individuals
+
Quarantine 50%Quarantine 75%
Mea
n U
rban
Infe
cted
Indi
vidu
als
Vaccination Rate
A Comparison of Vaccination Strategies
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
Eigenvalues of Equilibrium Point of Homogeneous System
Real part of eigenvalues Imaginary part of eigenvalues
Dominant Eigenvalue
Vaccination vs. Immigration