Globally, non-communicable diseases and obesity are growing in prevalence, particularly in malaria-threatened populations. Moreover, a large proportion of travellers are older and an estimated 1/3 of travellers to malaria countries have underlying medical conditions. This changing disease environment in malaria-prone populations warrants the need to assess how comorbidities impact the severity of malaria. Old age has been described in travellers as a risk factor for both serious and fatal malaria, and in patients aged 65 years with chronic diseases, longer hospital stays have been recorded. Nonetheless, no research has systematically examined how comorbidities impact malaria severity. In order to enhance public health strategies and to assist clinicians in identifying patients at risk, such assessment is necessary.

In this national retrospective review of imported malaria in Sweden for more than 20 years, it was assessed that comorbidity was correlated with extreme malaria in adults diagnosed, and any chronic disease in particular. Medical records from identified cases were provided by 18 hospitals managing malaria in Sweden. Data were retrieved regarding sociodemographics, travel history, chemoprophylaxis, clinical presentation, comorbidities, patient and healthcare delay (days from symptoms onset until healthcare contact, and from healthcare contact to diagnosis), intensive care, duration of hospital stay, treatment, and outcome, as well as routine blood chemistry and microbiology data including parasitemia, HIV, and hepatitis status. 

No one is completely immune to malaria, but individuals living in malaria-endemic countries often develop immunity to severe malaria. We are now seeing that people who have grown up in Sub-Saharan Africa and come to Sweden are gradually losing this immunity so that they are at the same risk of severe malaria after about 15 years as travellers born in Sweden. The population of travellers and migrants in Sweden who have been diagnosed with malaria, the multiple risk factors for extreme malaria and the long-term effects of the disease. Every year, 100 to 300 cases are diagnosed, a number which has varied in recent years, with growing migration and changes in travel behaviour. The findings are based on clinical data from all patients diagnosed between 1995 and 2015 with malaria in Sweden. We have also related the data to other registers, including the cancer registry of the National Board of Health and Welfare.

risk factors for severe malaria