Malaria risk in travelers.

Helena Hervius Askling,Jenny Nilsson,Anders Tegnell,Ragnhild Janzon,Karl Ekdahl

doi:10.3201/eid1103.040677

Helena Hervius Askling, Jenny Nilsson + Show 3 more

Open Access

https://doi.org/10.3201/eid1103.040677

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Abstract

Imported malaria has been an increasing problem in several Western countries in the last 2 decades. To calculate the risk factors of age, sex, and travel destination in Swedish travelers, we used data from the routine reporting system for malaria (mixture of patients with and without adequate prophylaxis), a database on travel patterns, and in-flight or visa data on Swedish travelers of 1997 to 2003. The crude risk for travelers varied from 1 per 100,000 travelers to Central America and the Caribbean to 357 per 100,000 in central Africa. Travelers to East Africa had the highest adjusted odds ratio (OR = 341, 95% confidence intervals [CI] 134-886) for being reported with malaria, closely followed by travelers to central Africa and West Africa. Male travelers as well as children <1-6 years of age had a higher risk of being reported with malaria (OR = 1.7, 95% CI 1.3-2.3 and OR = 4.8, 95% CI 1.5-14.8) than women and other age groups.

Highlights

Imported malaria has been an increasing problem in several Western countries in the last 2 decades
The calculated malaria risk per 100,000 travelers in 4 countries with alternative sources of travel information is shown in Table 5, with risk data based on the travel database, and the annual malaria incidence reported to World Health Organization (WHO) [15] as comparisons. These results are based on official reports of malaria, with data from one of the largest ongoing population-based surveys on travel patterns in Europe as denominator
The laboratory method of microscopy of a blood film for malaria is well defined, and the reporting of diagnosed malaria is believed to be relatively complete in Sweden

Summary

Introduction

Imported malaria has been an increasing problem in several Western countries in the last 2 decades. Other approaches to achieve risk estimates are case-control studies. In 1 such Danish study, the country-specific risk for acquiring malaria varied from 714 per 100,000 travelers to Ghana to 2.5 per 100,000 to Thailand [13]. No previous study based on national data over an extended period has related the number of cases of malaria diagnosed in returning travelers from malaria-endemic areas to continuously collected data on the total number of travelers to that same area. Through access to one of Europe’s largest ongoing surveys on travel patterns [14] and to data on reported malaria, we analyzed the risk factors for malaria in returning Swedish travelers from 1997 to 2003

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