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Borreliosis is the most frequently transmitted tick-borne disease in Europe. It is difficult to estimate the incidence of tick bites and associated diseases in the German population due to the lack of an obligation to register across all 16 federal states of Germany.
The aim of this study is to show that Google data can be used to generate general trends of infectious diseases on the basis of borreliosis and tick bites. In addition, the possibility of using Google AdWord data to estimate incidences of infectious diseases, where there is inconsistency in the obligation to notify authorities, is investigated with the perspective to facilitate public health studies.
Google AdWords Keyword Planner was used to identify search terms related to ticks and borreliosis in Germany from January 2015 to December 2018. The search volume data from the identified search terms was assessed using Excel version 15.23. In addition, SPSS version 24.0 was used to calculate the correlation between search volumes, registered cases, and temperature.
A total of 1999 tick-related and 542 borreliosis-related search terms were identified, with a total of 209,679,640 Google searches in all 16 German federal states in the period under review. The analysis showed a high correlation between temperature and borreliosis (
Our study provides insight into annual trends concerning interest in ticks and borreliosis that are relevant to the German population exemplary in the data of a large internet search engine. Public health studies collecting incidence data may benefit from the results indicating a significant correlation between internet search data and incidences of infectious diseases.
Borreliosis is the most frequently transmitted tick-borne disease in Europe. In 80%-90% of all cases, the disease presents with visible skin manifestations [
In 9 out of 16 federal states in Germany (Bavaria, Berlin, Brandenburg, Mecklenburg-West Pomerania, Rhineland-Palatinate, Saarland, Saxony, Saxony-Anhalt, and Thuringia), it is mandatory to report diagnosed borreliosis to the German federal government agency and research institute for disease control and prevention (Robert-Koch Institute). Thus, epidemiologic data for tick bites and associated diseases are based on measured, as well as estimated, values.
Google search analysis is a powerful tool to reflect the German population’s interest in specific topics because of its 94% market share [
Ticks are only active when ambient air temperature is 4-10 °C, so average temperature should be an important factor influencing tick-related queries. Therefore, weather data should provide insight into seasonal patterns [
This study aims to investigate the interest of the German population in tick bites and borreliosis by analyzing Google searches. Furthermore, this study aims to explore correlations between searches and whether that could provide information about real life tick bite occurrences, as well as associated diseases.
In this retrospective study, Google AdWords Keyword Planner was used to measure the search volume of terms related to tick bites and borreliosis across Germany from January 2015 to December 2018. The Keyword Planner is often used by advertisers to improve Google marketing campaigns and provides monthly search volumes estimated by Google. The term
In addition, search terms related to tick bites were identified using a keyword cluster for the German words for “tick bite” (“Zeckenbiss”) and “borreliosis” (“Borreliose”). Based on this cluster, Google AdWords Keyword Planner determined search terms to be analyzed. This data included only Google users with a German internet protocol address who used the German language. Furthermore, the German Climate Data Centre [
In 9 of 16 federal states in Germany (Bavaria, Berlin, Brandenburg, Mecklenburg-West Pomerania, Rhineland-Palatinate, Saarland, Saxony, Saxony-Anhalt, and Thuringia) covering 42% of the total German population, mandatory notification for the three most common Lyme borreliosis manifestations (erythema migrans, acute neuroborreliosis, and Lyme arthritis) has been achieved since 2013.
To assess whether the Google search volume correlates with registered cases of borreliosis, all registered cases from the federal states of Brandenburg, Mecklenburg-West Pomerania, Saxony, and Saxony-Anhalt were considered in the analysis, as complete statistics of registered data were only available for these on the website of the German federal government agency and research institute for disease control and prevention (Robert-Koch Institut).
The search volume data of the identified search terms was assessed using Excel version 15.23 (Microsoft Corporation). To describe the relationship between the investigated variables, we used SPSS version 24.0 (IBM Corp) to calculate the Pearson correlation coefficient (
In total, Google AdWords Keyword Planner identified 1999 search terms related to tick bites with a search volume of 26,080,530 in Germany from January 2015 to December 2018. The most frequently searched terms were “tick sting” (“Zeckenstich”; n=2,821,800, 10.82%), “tick” (“Zecke”; n=2,387,500, 9.15%), and “tick bite” (“Zeckenbiss”; n=178,850, 0.69%;
“tick-bite” (“Zeckenbiss”)
“tick sting” (“Zeckenstich”)
“tick” (“Zecke”)
“borreliosis” (“Borreliose”)
“borreliosis symptoms” (“Borreliose Symptome”)
“borreliosis” (“Borreliose”)
“borreliosis symptoms” (“Borreliose Symptome”)
“tick- bite” (“Zeckenbiss”)
“tick” (“Zecke”)
“symptoms borreliosis” (“Symptome Borreliose”)
Every year, an increase in search volume during summer months was observed (
Google searches in Germany in summer (April to September) vs winter months (October to March) for the top five tick- and borreliosis-related search terms in 2015-2018.
Seasonal variation of the two most common keywords searched for in Germany, “tick-bite” and “borreliosis,” from January 2015 to December 2018.
The analysis revealed a high correlation between temperature and borreliosis (
Google searches in Germany for "tick bite" and "borreliosis" correlated with the monthly average temperature in Germany in Celsius degrees between January 2015 to December 2018.
Furthermore, a high and very high correlation between google searches and registered cases in the referred federal states Brandenburg, Mecklenburg-West Pomerania, Saxony, and Saxony-Anhalt were detected (
Number of Google searches for "borreliosis" with registered cases of borreliosis in Brandenburg, Mecklenburg-West Pomerania, Saxony, and Saxony-Anhalt between January 2015 to December 2018.
Pearson correlation coefficients for Google searches for borreliosis and registered cases of borreliosis from January 2015 to December 2018 in Brandenburg, Mecklenburg-West Pomerania, Saxony, and Saxony-Anhalt.
Federal state | Registered cases, n | Google searches, n | Pearson correlation | |
Brandenburg | 6107 | 124,000 | 0.80 | <.001 |
Mecklenburg-West Pomerania | 3720 | 82,480 | 0.77 | <.001 |
Saxony | 7387 | 273,800 | 0.74 | <.001 |
Saxony-Anhalt | 2016 | 104,700 | 0.90 | <.001 |
The analysis of Google search volume related to tick bite and borreliosis identified an annual pattern that people tended to search more frequently during summer months. Therefore, a high correlation with average temperature was observed. Furthermore, a high correlation between registered cases of borreliosis in four German federal states was revealed.
One of the top five key terms of tick bite was borreliosis and vice versa. Therefore, we compared the two most common lay terms, tick bite and borreliosis. Interestingly, the search volume for the latter was higher. Especially in 2017 and 2018, a greater divergence between the keywords was observed, which can be explained by a greater awareness of associated diseases. This might be because of celebrities diagnosed with Lyme disease, such as Bastian Schweinsteiger and Justin Bieber, or because health education programs have taught people to make more accurate searches. Furthermore, media like smartphone apps and video games significantly improve knowledge of the disease and preventive measures [
Correlating weather data with the Google search volume showed seasonal trends, which were described in previous works concerning pruritus and identified inhabitants’ needs [
In some German federal states, it is mandatory to report borreliosis cases. Comparing numbers from Google searches and registered borreliosis cases shows a discrepancy. For example, in Brandenburg, the highest number of registered borreliosis cases in the reviewed years was 1743 in 2017. In comparison, the 2017 Google search volume for “borreliosis” in Brandenburg was 38,200, which is 22 times higher. This might be because the number of tick bites are much greater than the development of borreliosis symptoms. Additionally, not only affected people but also their relatives might search for information online, which explains a considerably higher number of search queries.
Walker [
We found statistically high correlations between registered borreliosis cases and Google search volume in four federal states. Previous studies identified Google data as a predictor of infectious disease outbreaks [
This study has some limitations. In Germany, Google accounts for 95% of search engine use, so Google data can depict the interests of the population as a whole. To transfer our findings to other countries, different market shares of Google over alternative search engines need to be taken into account. Although it is common among the whole population to make health-related searches, younger people tend to use the internet more often [
Our study provides insight into terms and fields of interest associated with tick bites and borreliosis, relevant to the German population. We found statistically high correlations between Google searches for borreliosis and registered cases of borreliosis across four German federal states. Accordingly, these results could help to estimate the incidence of borreliosis in the remaining 12 German federal states where it is not mandatory to report borreliosis. Furthermore, this approach could aid in the development and implementation of effective and sustainable awareness campaigns.
This work was supported by the department of Dermatology and Allergy, Technical University of Munich, School of Medicine, Munich, Germany.
None declared.