Modeling the risk of malaria for travelers to areas with stable malaria transmission

Abstract

Background: Malaria is an important threat to travelers visiting endemic regions. The risk of acquiring malaria is complex and a number of factors including transmission intensity, duration of exposure, season of the year and use of chemoprophylaxis have to be taken into account estimating risk.

Materials and methods: A mathematical model was developed to estimate the risk of non-immune individual acquiring falciparum malaria when traveling to the Amazon region of Brazil. The risk of malaria infection to travelers was calculated as a function of duration of exposure and season of arrival.

Results: The results suggest significant variation of risk for non-immune travelers depending on arrival season, duration of the visit and transmission intensity. The calculated risk for visitors staying longer than 4 months during peak transmission was 0.5% per visit.

Conclusions: Risk estimates based on mathematical modeling based on accurate data can be a valuable tool in assessing risk/benefits and cost/benefits when deciding on the value of interventions for travelers to malaria endemic regions.

Figure 1

Stochastic risk of catching falciparum malaria for travelers as a function of the period of the year they arrive and the time remaining in the area (the figure shows 20 iterations of the 1000 simulated).

Figure 2

In the figure we show in the x-axis time in days. It starts arbitrarily at day 500 and illustrates seasonal variation of a mosquito population (susceptible and infected). The arrows define the relative season and seasonal impact on the susceptible mosquitoes populations (thin line) over the year. The figure also shows the infected mosquitoes (thick line) amplified 20 times.