Significance Disease surveillance systems largely focus on infectious diseases with high mortality, whereas less severe diseases often go unreported. Using chicken pox as an example, we demonstrate that Internet queries can be used as a proxy for disease incidence when reporting is lacking. We established that Google Trends accurately reflected clinical cases in countries with surveillance, and thus population-level dynamics of chicken pox. Then, we discovered robust seasonal variation in query behavior, with a striking latitudinal gradient on a global scale. Next, we showed that real-time data-mining of queries could forecast the timing and magnitude of outbreaks. Finally, our analyses revealed that countries with government-mandated vaccination programs have significantly reduced seasonality of queries, indicating vaccination efforts mitigated chicken pox outbreaks. 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.
【저자키워드】 vaccination, Disease dynamics, internet search, chicken pox, forecast modeling,