Geographical and temporal trends in imported infections from the tropics requiring inpatient care at the Hospital for Tropical Diseases, London - a 15 year study

Abstract

Background: Understanding geographic and temporal trends in imported infections is key to the management of unwell travellers. Many tropical infections can be managed as outpatients, with admission reserved for severe cases.

Methods: We prospectively recorded the diagnosis and travel history of patients admitted between 2000 and 2015. We describe the common tropical and non-tropical infectious diseases and how these varied based on region, reason for travel and over time.

Results: A total of 4362 admissions followed an episode of travel. Falciparum malaria was the most common diagnosis (n=1089). Among individuals who travelled to Africa 1206/1724 (70.0%) had a tropical diagnosis. The risk of a tropical infection was higher among travellers visiting friends and relatives than holidaymakers (OR 2.8, p<0.001). Among travellers to Asia non-tropical infections were more common than tropical infections (349/782, 44.6%), but enteric fever (117, 33.5%) of the tropical infections and dengue (70, 20.1%) remained important. The number of patients admitted with falciparum malaria declined over the study but those of enteric fever and dengue did not.

Conclusions: Most of those arriving from sub-Saharan Africa with an illness requiring admission have a classical tropical infection, and malaria still predominates. In contrast, fewer patients who travelled to Asia have a tropical diagnosis but enteric fever and dengue remain relatively common. Those visiting friends and relatives are most likely to have a tropical infection.

Keywords: Enteric fever; Febrile illness; Imported infections; Malaria; Travellers.

Figure 1.

Reason for travel to different regions of the world. The pie charts show the reason for travel in individuals who travelled to each region of the world. Larger pie charts represent regions to which more individuals had travelled. VRF: visiting friends and relatives.

Figure 2.

Cause of admission following travel to different regions of the world. The pie charts show the reason of admission in individuals who travelled to each region of the world. Larger pie charts represent regions to which more individuals had travelled. LRTI: lower respiratory tract infection; PVI: presumed viral infection; SSTI: skin and soft tissue infection; UTI: urinary tract infection.

Figure 3.

Admissions due to falciparum malaria. The number of admissions per year due to falciparum malaria declined over the period of the study. For comparison the number of admissions related to leishmaniasis, non-falciparum malaria and enteric fever data are also provided. There was no significant change in admission patterns for these three diagnoses.