Trends in imported malaria to Basel, Switzerland

Due to persistent international travel and immigration trends, imported malaria remains to be of clinical and public health importance in nonendemic countries. The aim of this study was to investigate trends in imported malaria over a period of more than three decades.

We assessed travel history, demographic characteristics, and clinical course with special regard to malaria diagnosis and intensive care unit (ICU) admission of patients diagnosed with malaria. The sample comprised 109 patients with the diagnosis of malaria according to the International Statistical Classification of Diseases and Related Health Problems (ICD)-coding system (versions 9 and 10) at the University Hospital and at a teaching hospital in Basel between January 1994 and June 2004. Changes in clinical management and outcomes were compared with previous studies at the same institutions dating back to the 1970s.

The most common reason for travel was to visit friends and relatives in the country of origin (37%), and most infections were acquired in Africa (82%), with Plasmodium falciparum malaria the most frequently found parasite (84%). The mean time between first symptoms and the diagnosis of malaria was 4 days (range 0.5-31 d). Delay in diagnosis occurred in 14% of cases, and 37% of hospitalized patients were referred to the ICU. In 22% of referred cases, high parasitemia (>2%) according to internal criteria was a reason for referral. The course of disease remained mild in the great majority (90%) of patients, and none of the patients died.

Prompt and specific diagnosis of malaria could be improved. Malaria-associated mortality was reduced over time. As ICU referral showed to be inappropriately high in relation to a moderate clinical course of several admitted patients, criteria for ICU admission should be reevaluated. The trend toward malaria in patients originating from endemic areas suggests that preventive travel advice should specifically address these patients.