• Journal: Proceedings of the National Academy of Sciences
  • Date: June 14, 2016
  • DOI: 10.1073/pnas.1523941113
  • Category: Scientific Research


Kevin M. Bakker, Micaela Elvira Martinez-Bakker, Barbara Helm, and Tyler J. Stevenson used chicken pox to study how well internet queries and Google Trends reflected the incidence of less-severe diseases. By using the varicella database from Project Tycho, the authors found that Google Trends accurately reflected clinical cases in countries with surveillance and noted seasonal variation in query behavior. The analysis also showed that vaccination programs had a significant impact on reducing chicken pox outbreaks.


Kevin M. Bakker

Micaela Elvira Martinez-Bakker

Barbara Helm

Tyler J. Stevenson

Related Project Tycho Datasets

United States of America - Varicella


Public health surveillance systems are important for tracking disease dynamics. In recent years, social and real-time digital data sources have provided new means of studying disease transmission. Such affordable and accessible data have the potential to offer new insights into disease epidemiology at national and international scales. We used the extensive information repository Google Trends to examine the digital epidemiology of a common childhood disease, chicken pox, caused by varicella zoster virus (VZV), over an 11-y period. We (i) report robust seasonal information-seeking behavior for chicken pox using Google data from 36 countries, (ii) validate Google data using clinical chicken pox cases, (iii) demonstrate that Google data can be used to identify recurrent seasonal outbreaks and forecast their magnitude and seasonal timing, and (iv) reveal that VZV immunization significantly dampened seasonal cycles in information-seeking behavior. Our findings provide strong evidence that VZV transmission is seasonal and that seasonal peaks show remarkable latitudinal variation. We attribute the dampened seasonal cycles in chicken pox information-seeking behavior to VZV vaccine-induced reduction of seasonal transmission. These data and the methodological approaches provide a way to track the global burden of childhood disease and illustrate population-level effects of immunization. The global latitudinal patterns in outbreak seasonality could direct future studies of environmental and physiological drivers of disease transmission.

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