Estimating the malaria risk of African mosquito movement by air travel

Abstract

Background: The expansion of global travel has resulted in the importation of African Anopheles mosquitoes, giving rise to cases of local malaria transmission. Here, cases of 'airport malaria' are used to quantify, using a combination of global climate and air traffic volume, where and when are the greatest risks of a Plasmodium falciparum-carrying mosquito being importated by air. This prioritises areas at risk of further airport malaria and possible importation or reemergence of the disease.

Methods: Monthly data on climate at the World's major airports were combined with air traffic information and African malaria seasonality maps to identify, month-by-month, those existing and future air routes at greatest risk of African malaria-carrying mosquito importation and temporary establishment.

Results: The location and timing of recorded airport malaria cases proved predictable using a combination of climate and air traffic data. Extending the analysis beyond the current air network architecture enabled identification of the airports and months with greatest climatic similarity to P. falciparum endemic regions of Africa within their principal transmission seasons, and therefore at risk should new aviation routes become operational.

Conclusion: With the growth of long haul air travel from Africa, the identification of the seasonality and routes of mosquito importation is important in guiding effective aircraft disinsection and vector control. The recent and continued addition of air routes from Africa to more climatically similar regions than Europe will increase movement risks. The approach outlined here is capable of identifying when and where these risks are greatest.

Figure 1

Total incoming passenger numbers per country from malaria endemic African airports for 2000.

Figure 2

Countries in which confirmed or probable cases of airport malaria have been reported. Data taken from Gratz (2000)[6].

Figure 3

Month in which European airport malaria cases occurred [7, 8, 14, 25, 38-62] (where date is provided).

Figure 4

Number of months in a year that the climate at each international airport is sufficiently similar to that of a SSA airport within its primary malaria transmission season for imported P. falciparum-carrying An. gambiae survival.

Figure 5

Month of peak climatic similarity with climatically closest malaria-endemic SSA airport.