Infodemiology of flu: Google trends-based analysis of Italians’ digital behavior and a focus on Sars-CoV-2 Italy.


Flu; Sars-Cov-2; Google Trends; Big Data; Medical Informatics Computing; Italy.


Introduction: The aim of the current study was to assess if the frequency of internet searches for influenza are aligned with Italian National Institute of Health (ISS) cases and deaths. Also, we evaluate the distribution over time and the correlation between search volume of flu and flu symptoms with reported new cases of Sars-CoV-2.

Materials and methods: The reported cases and deaths of flu and the reported cases of Sars-CoV-2 were selected from the reports of ISS, the data have been aggregated by week. The search volume provided by Google Trends (GT) has a relative nature and is calculated as a percentage of query related to a specific term in connection with a determined place and time-frame.

Results: The strongest correlation between GT search and influenza cases was found at a lag of +1 week particularly for the period 2015-2019. A strong correlation was also found at a lag of +1 week between influenza death and GT search. About the correlation between GT search and Sars-CoV-2 new cases the strongest correlation was found at a lag of +3 weeks for the term flu.

Conclusion: In the last years research in health care has used GT data to explore public interest in various fields of medicine. Caution should be used when interpreting the findings of digital surveillance.


1. Rizzo C, Bella A, Viboud C, Simonsen L, Miller MA, Rota MC, et al. Trends for influenza-related deaths during pandemic and epidemic seasons, Italy, 1969-2001. Emerg Infect Dis. 2007;13(5):694-9.
2. Centers for Disease Control and Prevention. Influenza (Flu) 2019 [Available from:
3. Brussow H. The Novel Coronavirus - A Snapshot of Current Knowledge. Microb Biotechnol. 2020;13(3):607-12.
4. Pascarella G, Strumia A, Piliego C, Bruno F, Del Buono R, Costa F, et al. COVID-19 diagnosis and management: a comprehensive review. J Intern Med. 2020.
5. Ningthoujam R. COVID 19 can spread through breathing, talking, study estimates. Curr Med Res Pract. 2020.
6. Huang Q, Deng X, Li Y, Sun X, Chen Q, Xie M, et al. Clinical characteristics and drug therapies in patients with the common-type coronavirus disease 2019 in Hunan, China. Int J Clin Pharm. 2020:1-9.
7. Signorelli C, Odone A, Gianfredi V, Bossi E, Bucci D, Oradini-Alacreu A, et al. The spread of COVID-19 in six western metropolitan regions: a false myth on the excess of mortality in Lombardy and the defense of the city of Milan. Acta Biomed. 2020;91(2):23-30.
8. Odone A, Delmonte D, Scognamiglio T, Signorelli C. COVID-19 deaths in Lombardy, Italy: data in context. Lancet Public Health. 2020.
9. Ministry of Health. Covid-19 - Situazione in Italia 2020 [Available from:
10. Gianfredi V, Moretti M, Fusco Moffa I. Burden of measles using disability-adjusted life years, Umbria 2013-2018. Acta Biomed. 2020;91(3-S):48-54.
11. Mahroum N, Bragazzi NL, Sharif K, Gianfredi V, Nucci D, Rosselli R, et al. Leveraging Google Trends, Twitter, and Wikipedia to Investigate the Impact of a Celebrity's Death From Rheumatoid Arthritis. J Clin Rheumatol. 2018;24(4):188-92.
12. Provenzano S, Santangelo OE, Giordano D, Alagna E, Piazza D, Genovese D, et al. Predicting disease outbreaks: evaluating measles infection with Wikipedia Trends. Recenti Prog Med. 2019;110(6):292-6.
13. Gianfredi V, Bragazzi NL, Nucci D, Martini M, Rosselli R, Minelli L, et al. Harnessing Big Data for Communicable Tropical and Sub-Tropical Disorders: Implications From a Systematic Review of the Literature. Front Public Health. 2018;6:90.
14. Bragazzi NL, Barberis I, Rosselli R, Gianfredi V, Nucci D, Moretti M, et al. How often people google for vaccination: Qualitative and quantitative insights from a systematic search of the web-based activities using Google Trends. Hum Vaccin Immunother. 2017;13(2):464-9.
15. Gianfredi V, Bragazzi NL, Mahamid M, Bisharat B, Mahroum N, Amital H, et al. Monitoring public interest toward pertussis outbreaks: an extensive Google Trends-based analysis. Public Health. 2018;165:9-15.
16. Santangelo OE, Provenzano S, Piazza D, Giordano D, Calamusa G, Firenze A. Digital epidemiology: assessment of measles infection through Google Trends mechanism in Italy. Ann Ig. 2019;31(4):385-91.
17. Istituto Superiore di Sanità. Rapporto Influnet. Aggiornamento 8 maggio 2020 2020 [Available from:
18. Google Trends. Scopri quali ricerche si fanno nel mondo 2020 [Available from:
19. StataCorp. Stata Statistical Software. In: Station C, editor.: StataCorp LP; 2015.
20. The Lancet. COVID-19: fighting panic with information. Lancet. 2020;395(10224):537.
21. Gianfredi V, Dallagiacoma G, Provenzano S, Santangelo OE. Factors predicting health science students' willingness to be vaccinated against seasonal flu during the next campaign. Ann Ist Super Sanita. 2019;55(3):209-16.
22. Gentile L, Cuda A, Dallagiacoma G, Provenzano S, Santangelo OE, Navaro M, et al. Opinion, knowledge and attitude of public health residents towards the new mandatory vaccination law in Italy. J Public Health (Berl). 2020.
23. World Health Organization. Guidance on routine immunization services during COVID-19 pandemic in the WHO European Region. 2020 [Available from:
24. Salathe M. Digital epidemiology: what is it, and where is it going? Life Sci Soc Policy. 2018;14(1):1.
25. Eckmanns T, Füller H, Roberts SL. Digital epidemiology and global health security; an interdisciplinary conversation. Life Sci Soc Policy. 2019;15(1):2. Published 2019 Mar 19. doi:10.1186/s40504-019-0091-8
26. Signorelli C, Odone A, Conversano M, Bonanni P. Deaths after Fluad flu vaccine and the epidemic of panic in Italy. BMJ. 2015;350:h116.
27. Gianfredi V, Odone A, Fiacchini D, Rosselli R, Battista T, Signorelli C. Trust and reputation management, branding, social media management nelle organizzazioni sanitarie: sfide e opportunità per la comunità igienistica italiana. J Prev Med Hyg. 2019;60(3):E108-E9.
28. Bragazzi NL, Gianfredi V, Villarini M, Rosselli R, Nasr A, Hussein A, et al. Vaccines Meet Big Data: State-of-the-Art and Future Prospects. From the Classical 3Is ("Isolate-Inactivate-Inject") Vaccinology 1.0 to Vaccinology 3.0, Vaccinomics, and Beyond: A Historical Overview. Front Public Health. 2018;6:62.
29. Gianfredi V, Grisci C, Nucci D, Parisi V, Moretti M. [Communication in health.]. Recenti Prog Med. 2018;109(7):374-83.
30. Gianfredi V, Balzarini F, Gola M, Mangano S, Carpagnano LF, Colucci ME, et al. Leadership in Public Health: Opportunities for Young Generations Within Scientific Associations and the Experience of the "Academy of Young Leaders". Front Public Health. 2019;7:378.