Using Google Trends for public health surveillance : a case study of influenza in Hong Kong

Abstract

Background: Google Corporation developed Google Flu Trends, in order to monitor influenza activity initially in the United States. It has been expanded to other countries, however, Google Flu Trends does not exist for Hong Kong. The Hong Kong Centre for Health Protection does not incorporate internet search data into their influenza surveillance program. The purpose of this study was to investigate the correlation between influenza surveillance data in Hong Kong and Google Trends in Hong Kong, and whether Google Trends or other big data sources should be incorporated in public health surveillance in Hong Kong.

Method: Weekly influenza surveillance data between January 2009 through to May 2015 was obtained from the Hong Kong Centre for Health Protection (CHP) website. Internet search results on a weekly basis were downloaded from the Google Trends website. Pearson’s correlation coefficients have been calculated to compare the Google Trends search results with influenza in Hong Kong, for the overall time period.

Results: The results show that in Hong Kong, Google Trends data using English search terms have a moderate correlation with conventional methods of influenza surveillance. The data from Google Trends, especially those related to ILI symptoms, can be used as a complementary source of data for influenza surveillance in Hong Kong. There was no Google Trend data for several search terms identified. For five search terms, ‘Fever,’ ‘Flu Symptoms,’ ‘Influenza A,’ ‘Cough,’ and ‘Virus,’ there was data available from Google Trends and a positive correlation with influenza activity. The search term ‘Flu Symptoms’ had the highest correlation with influenza, at 0.4702.

Conclusions: This study has shown that Google Trends in Hong Kong can be used as an additional, complementary data source, for influenza surveillance in Hong Kong. Additional research should be done, including determining the correlation between influenza search terms in the Chinese language and influenza. Enhancements can be made to Google Trends to improve the output of data. Specifically, Google Trends should produce results for all search terms, not just some. Google Trends should also produce data on a consistent basis, possibly giving the user the ability to select weekly or monthly output. Technology will become increasingly important in public health surveillance in the future. With improvements, internet search engines must be used, helping to detect early signs of disease outbreaks, and help estimate future local disease activity.