Malaria in travellers and migrants : disease severity and long term effects

Malaria is a potentially fatal infection, where prompt and correct management is crucial for the outcome. Despite international efforts to reduce transmission, there are over 200 million new malaria cases with approximately 400 000 deaths per year, the majority occurring in Sub-Saharan Africa. Globalization, in terms of travel and migration, brings malaria also to non-endemic countries. Approximately 100-300 cases of malaria are diagnosed in Sweden per year, with significant variations during the last years due to changes in travel and migration patterns. Despite a well-established national surveillance, the clinical presentation, outcome and risk factors for severe malaria have not previously been described. Individuals growing up in endemic areas, gradually develop immunity, first to the most severe forms of malaria and eventually also to mild disease. However, how long protection against severe disease is maintained in individuals that are no longer exposed is not clear. Moreover, non-communicable diseases and obesity increase globally, including in travellers and populations living in malaria endemic areas, but the impact of comorbidities on the severity of malaria has not been systematically assessed. In addition to the well-described acute complications, malaria may cause long-term consequences that have been much less investigated. The association between malaria and Burkitt lymphoma in African children is since long recognized, but it is unknown if malaria is related to other cancer forms. In this thesis, we have investigated risk factors for severe disease in travellers and migrants diagnosed with malaria in Sweden 1995-2015. Moreover, by using the Swedish surveillance system and national health and demographic registers, we studied long-term consequences of malaria in terms of lymphoma and other cancer. In Study I, we assessed the risk of severe P. falciparum in immigrants from Sub-Saharan Africa and non-immune travellers. We showed that duration of residency in a malaria-free country was associated ...