Yellow Fever in Senegal: Strategies for Control

1. 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

3. World Health Organization: Communicable Diseases Epidemiological Report (2003)

4. Three patch model:Urban, Village, and Forest ~ 100,000 individuals with infection coming from contact with infected individuals from the village patch U V ~ 10,000 individuals with infection coming from contact with infected individuals from the forest patch F ~ 1,000 individuals with constant rate of infection from forest (monkey) reservoir

5. Urban Village Forest infection from the reservoir

6. rate of infection from reservoir = 0.0001/day transmission-rate = 0.12/infected individual/day recovery rate = 0.10/day contact probability between forest-village = 0.01/infected individual/day contact probability between village-urban = 0.01/infected individual/day birth rate = death rate = 0.0001/day Number of Infected Individuals Number of Infected Individuals ~ 2.3 years Time (days) Time (days)

7. Vaccination = + Fraction of Days Sampled vaccination rate = 2.5e-4 vaccinations/person/day Number of Infected Individuals

8. A Comparison of Vaccination Strategies Quarantine 50% Quarantine 75% Mean Urban Infected Individuals Vaccination Rate

9. Further Work: • 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 • pulsed vaccinations • seasonal fluctuations • mosquito population • mosquito-based control - spraying - mosquito nets • less parameter-sensitive models

10. Eigenvalues of Equilibrium Point of Homogeneous System Real part of eigenvalues Imaginary part of eigenvalues

11. Dominant Eigenvalue

12. Vaccination vs. Immigration