LAUSR

Influenza epidemics are a major public health concern, causing hundreds of thousands of deaths worldwide each year. Studies suggest a possible beneficial use of online activity monitoring in influenza epidemics surveillance and forecasting. Until the present time Google search user activity has not been assessed for forecasting of influenza epidemics in Lithuania. Though this country has 2.8 million residents and mother language of majority of them is Lithuanian. Thus, we assessed a possible use of Google Trends for forecasting of influenza epidemics in Lithuania. We translated Google queries most commonly analyzed for forecasting of influenza epidemics by other researchers to Lithuanian language and used Google Trends to retrieve data about frequency of their usage in Google Search during the period of last 5 years. We assessed cross-correlation between usage frequency of each query with an incidence rate of acute upper respiratory tract infections (AURTI) and influenza. Providing data available 2 weeks before the first announcement of influenza epidemic, for the query with the strongest correlation we constructed the autoregressive integrated moving average (ARIMA) model and used it to make a forecast for upcoming 9 weeks. Then we assessed the cross-correlation between the forecast and incidence rate of AURTI and influenza. We found the strongest correlation with an incidence rate of AURTI and influenza for a keyword ‘gripas’ (correlation coefficients were 0.805 and 0.803 for lags of 0 and 1, respectively, p = 0.001). 75% true values of the query usage frequency fell into 95% confidence interval of the forecast by ARIMA(1,0,0)(0,1,0)[52] model. Incidence rate of AURTI and influenza correlated with the forecast having coefficients of 0.902 and 0.733 for lags of 0 and 1, respectively (p = 0.007). Query ‘gripas’ demonstrated the possible beneficial use in forecasting influenza epidemics 2 weeks before their onset. Google Trends has a potential to be used for forecasting influenza epidemics in Lithuania. Google Search query ‘gripas’ proved the most beneficial for forecasting incidence rate of upper respiratory tract infections and influenza in Lithuania.