Abstract
BackgroundWeb queries are now widely used for modeling, nowcasting and forecasting influenza-like illness (ILI). However, given that ILI attack rates vary significantly across ages, in terms of both magnitude and timing, little is known about whether the association between ILI morbidity and ILI-related queries is comparable across different age-groups. The present study aimed to investigate features of the association between ILI morbidity and ILI-related query volume from the perspective of age.MethodsSince Google Flu Trends is unavailable in Italy, Google Trends was used to identify entry terms that correlated highly with official ILI surveillance data. All-age and age-class-specific modeling was performed by means of linear models with generalized least-square estimation. Hold-out validation was used to quantify prediction accuracy. For purposes of comparison, predictions generated by exponential smoothing were computed.ResultsFive search terms showed high correlation coefficients of > .6. In comparison with exponential smoothing, the all-age query-based model correctly predicted the peak time and yielded a higher correlation coefficient with observed ILI morbidity (.978 vs. .929). However, query-based prediction of ILI morbidity was associated with a greater error. Age-class-specific query-based models varied significantly in terms of prediction accuracy. In the 0–4 and 25–44-year age-groups, these did well and outperformed exponential smoothing predictions; in the 15–24 and ≥ 65-year age-classes, however, the query-based models were inaccurate and highly overestimated peak height. In all but one age-class, peak timing predicted by the query-based models coincided with observed timing.ConclusionsThe accuracy of web query-based models in predicting ILI morbidity rates could differ among ages. Greater age-specific detail may be useful in flu query-based studies in order to account for age-specific features of the epidemiology of ILI.
Highlights
Seasonal influenza is a relatively predictable annual event which causes approximately half a million deaths worldwide every year [1]
Querybased prediction of influenza-like illness (ILI) morbidity was associated with a greater error
The accuracy of web query-based models in predicting ILI morbidity rates could differ among ages
Summary
Seasonal influenza is a relatively predictable annual event which causes approximately half a million deaths worldwide every year [1]. Glass et al [8] pointed out the importance of high-school students in the local spread of the virus, while Schanzer et al [9] doubted the hypothesis that younger school-age children drive epidemic waves. These latter authors demonstrated that, during influenza seasons in which H3N2 strains predominated, young adults aged 20–29 years led teenagers aged 10–19 years by about 4 days, while during the last pandemic this latter group led both 4–9-year-olds and young adults [9]. The present study aimed to investigate features of the association between ILI morbidity and ILI-related query volume from the perspective of age
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
