Increased incidence of Lyme borreliosis in southern Sweden following mild winters and during warm, humid summers.

Document type: Journal Articles
Article type: Original article
Peer reviewed: Yes
Author(s): Louise Bennet, Anders Halling, Johan Berglund
Title: Increased incidence of Lyme borreliosis in southern Sweden following mild winters and during warm, humid summers.
Journal: European journal of clinical microbiology & infectious diseases
Year: 2006
Volume: 25
Issue: 7
Pagination: 426-432
ISSN: 0934-9723
Publisher: SPRINGER
URI/DOI: 10.1007/s10096-006-0167-2
ISI number: 000239084200002
Organization: Blekinge Institute of Technology
Department: School of Health Science (Sektionen för hälsa)
School of Health Science S-371 79 Karlskrona
+46 455 38 50 00
http://www.bth.se/hal/
Language: English
Abstract: The aim of the present study was to investigate the long-term incidence rate of Lyme borreliosis and, additionally, to determine whether a correlation exists between climatic factors and summer-season variations in the incidence of Lyme borreliosis. Climatic variability acts directly on tick population dynamics and indirectly on human exposure to Lyme borreliosis spirochetes. In this study, conducted in primary healthcare clinics in southeastern Sweden, electronic patient records from 1997-2003 were searched for those that fulfilled the criteria for erythema migrans. Using a multilevel Poisson regression model, the influence of various climatic factors on the summer-season variations in the incidence of erythema migrans were studied. The mean annual incidence rate was 464 cases of erythema migrans per 100,000 inhabitants. The incidence was significantly higher in women than in men, 505 and 423 cases per 100,000 inhabitants, respectively (p<0.001). The summer-season variations in the erythema migrans incidence rate correlated with the monthly mean summer temperatures (incidence rate ratio 1.12; p<0.001), the number of winter days with temperatures below 0 degrees C (incidence rate ratio 0.97; p<0.001), the monthly mean summer precipitation (incidence rate ratio 0.92; p<0.05), and the number of summer days with relative humidity above 86% (incidence rate ratio 1.04; p<0.05). In conclusion, Lyme borreliosis is highly endemic in southeastern Sweden. The climate in this area, which is favourable not only for human tick exposure but also for the abundance of host-seeking ticks, influences the summer-season variations in the incidence of Lyme borreliosis.
Subject: Medical Sciences
Public Health\General
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