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Declining incidence of malaria imported into the UK from West Africa

Ron H Behrens13*, Bernadette Carroll1, Valerie Smith2 and Neal Alexander3

Author Affiliations

1 Department of Travel Medicine, Hospital for Tropical Diseases, Capper St, London, WC1 6JB, UK

2 HPA Malaria Reference Laboratory, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK

3 Clinical Research Unit (RHB) and Infectious Diseases Epidemiology Unit (NA) London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK

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Malaria Journal 2008, 7:235  doi:10.1186/1475-2875-7-235

Published: 10 November 2008

Abstract

Background

Two thirds of all falciparum malaria cases reported in the United Kingdom (UK) are acquired in West Africa (WA). To ensure recommendations and guidelines for malaria prophylaxis in travellers to West Africa correlate to the risk of infection, a study was undertaken to examine recent trends and predict future patterns of imported malaria acquired by UK residents visiting West Africa and West African visitors to the UK between 1993 and 2006.

Methods and Results

Using passenger numbers and malaria surveillance reports, the data revealed a 2.3-fold increase in travel to West Africa with a five-fold increase in travelers visiting friends and relatives (VFR). Malaria incidence fell through the study period, the greatest decline noted in VFR with a fall from 196 cases/1,000 person-years to 52 cases/1,000 person-years, 9.8% per year p < 0.0001. The risk for travellers from the UK visiting for other reasons declined 2.7 fold, at an annual decrease of 7.0%, with the incidence in West African visitors to the UK falling by 2.3 fold, a rate of 7.9% annually.

Discussion

The reduction in incidence among all three groups of travellers may be explained by several factors; changing chemoprophylaxis usage and/or increased travel in urban areas where malaria risk has declined over the past decade, or widespread reduction in malaria transmission in West Africa.

Conclusion

With the reduction in malaria incidence seen in both visitors to and from West Africa, the most rational explanation for these findings is a fall in malaria transmission in West Africa, which may require a change in chemoprophylaxis policy for UK travelers over the next 5–10 years.