The association between climate change and Lyme disease incidence in Northern European countries by the Baltic and North Seas: An ecological time-series study

Climate change is a complex problem that often disproportionately affects global health, including its influence on microbial ecosystems, which can lead to disease outbreaks such as Lyme disease (LD). However, the extent of climate variability and its influence on the spread of the most common vector-borne disease in countries that neighbor the Baltic Sea and North Sea have not been fully quantified. Therefore, this study focuses on an approach that measures the magnitude of the (LD) burden on the most at-risk European countries due to climate change. In this ecological study, the correlation between disease incidence over the years and climate change was tested using a Spearman correlation test, and the change in incidence of LD during the period 2000-2024 was assessed using Generalized Linear Models (GLMs), with a negative binomial distribution to handle overdispersion. The study found a strong positive relationship after adjusting for the tick lifecycle using lagged climate variables of two years to higher rates of LD in countries bordering the Baltic and North Seas. Most importantly, a unit increase in precipitation (mm/year), after adjusting for delayed effects, is associated with a higher disease rate (IRR Range= 1.15-1.24). Two years of delayed temperature effect is with a similar relationship (IRR range = 1.11-1.27). These findings suggest that the disproportionate climate change in the region influences the spread and burden of the disease in the north European temperate climate, even after controlling for delays. Compared to previous research, this study is concerned with the regional impact of climate change on microbial life and disease spillover, which causes public health problems. There is an urgent need for a collaborative and comprehensive program to include environmental, human, animal and vector data factors for future research to aid in disease control.