Climate Change and Encephalitis

The potential impact of climate change on the transmission risk of tick-borne encephalitis in Hungary

Kyeongah Nah, Ákos Bede-Fazekas, Attila János Trájer, and Jianhong Wu

Summarized by Kailey McCain

What data were used? The data collected for this study includes the monthly average temperature values in Hungary from the years 1961-1990. Specifically, for the past climate data,researchers used the CarpatClim-Hu database. For future climate predictions, the researchers used two distinct climate models: ALADIN-Climate 4.5 and RegCM 3.1. Additionally, previously established models for Tick-borne Encephalitis virus (i.e., a human viral infectious disease) transmission was used. Models help us hypothesize how different scenarios will look, by allowing us to input a lot of different types of data to understand large future patterns, like the one in this article! 

Methodology: By using the previous climate data for the years 1961-1990, the researchers established a predictive warming model for the years 2021-2050 and 2071-2100 in Hungary. This data was then compared to the tick-borne encephalitis virus (TBEV) transmission model to establish correlations between the data sets. This model broke down the transmission into various factors: reproduction numbers, duration of infestation, and density. The dynamics of transmission can be visualized in figure 1.

Figure 1: This figure shows an extensive diagram of how an infected tick spreads the disease to humans, livestock, and other animals. The inner circle represents the stages from larva, to nymph, to mature tick; then it branches to external transmission.

Results: The predictive climate model showed a steady increase in temperature for the age ranges 2021-2050 and 2071-2100, and the TBEV model resulted in an increase in tick population and transmission. These increases can be positively correlated (linked) to warming climate because previous data shows that a higher temperature speeds up the rate of sexual maturity in ticks; meaning, this allows the tick to reproduce at an increased rate. Moreover, research has shown that a warming climate leads to the elongation of tick questing season; which increases the chance for transmission. When a tick is questing (shown in figure 2), it is strategically placed on vegetation in order to grab a hold of by passers. 

Figure 2: This image represents a questing tick sitting on the edge of a lead with their legs spread out, and ready for attachment.

Why is this study important? This study is important because it shows the dynamic effects climate change has on global health. It also conveys an important message that the prevention of climate change is not only a biological and geological problem, but a public health problem, too. This means that solutions for reducing the impacts of climate change have to be creative and have to be from a lot of different types of researchers! 

The big picture: This study helps us understand the ways in which infectious diseases, (e.g., Tick-Borne Encephalitis Virus) are affected by climate change. As well as giving a glimpse into the future of what disease transmission will look like if prevention protocols are not put in place.

Citation: Kyeongah Nah, Ákos Bede-Fazekas, Attila János Trájer, & Jianhong Wu. (2020). The potential impact of climate change on the transmission risk of tick-borne encephalitis in Hungary. BMC Infectious Diseases, 20(1), 1–10.

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