Association between incidence of Lyme disease and spring-early summer season temperature changes in Hungary--1998-2010.

The increase of Lyme borreliosis (LB) can be expected due to climate change, while the distribution of the disease and annual activity of the vector and host animals depend on several factors of the environment. The presented study aimed to assess expressly the spring season temperature dependence on the incidence of LB in Hungary. The weekly LB data were obtained from the National Epidemiologic and Surveillance System for a period of 13 years--1998-2010. Daily temperature data were derived from the European Climate Assessment and Dataset. The association was studied at national level, descriptive statistics and linear regression models were applied. A significant increasing trend was observed in the mean temperature of the analysed years (0.052°C per year). The annual LB incidence doubled during the 13 year period. The incidence rates of the periods 1998-2001 and 2007-2010 were 11.1 resp. 17.0 per 100,000. The start of a steep increase in weekly LB incidence (0.1 per 100,000) shifted significantly by 3 weeks earlier, the start date of spring showed similar trend (p=0.0041). LB incidence increased more steadily in spring than in summer, with 79% of the increase being reported during weeks 15-28, with maximum rates of increase occurring in weeks 23-25. The trend was significant between the weeks 15-28. In the warmer years with 19.02°C mean temperature in May and June, the LB incidence curve reached the annual peak 2-3 weeks earlier, and the descending phase of the curve started earlier than in the colder years with 17.06°C of the same period.