R. Marquet, A. Bartelds, S. Van-noort, C. Koppeschaar, J. Paget et al., Internet-based monitoring of influenza-like illness (ILI) in the general population of the Netherlands during the 2003???2004 influenza season, BMC Public Health, vol.20, issue.Suppl 3, p.242, 2006.
DOI : 10.1007/s10654-004-5099-5

D. Paolotti, A. Carnahan, V. Colizza, K. Eames, J. Edmunds et al., Web-based participatory surveillance of infectious diseases: the Influenzanet participatory surveillance experience, Clinical Microbiology and Infection, vol.20, issue.1, pp.17-21, 2014.
DOI : 10.1111/1469-0691.12477

D. Centers, . Control, and . Prevention, Updated guidelines for evaluating public health surveillance systems. Recommendations from the Guidelines Working Group, pp.50-131, 2001.

J. Ginsberg, M. Mohebbi, R. Patel, L. Brammer, M. Smolinski et al., Detecting influenza epidemics using search engine query data, Nature, vol.36, issue.7232, pp.1012-1014, 2009.
DOI : 10.1038/nature07634

C. Pelat, C. Turbelin, A. Bar-hen, A. Flahault, and A. Valleron, More Diseases Tracked by Using Google Trends, Emerging Infectious Diseases, vol.15, issue.8, pp.1327-1328, 2009.
DOI : 10.3201/eid1508.090299

J. Brownstein, C. Freifeld, B. Reis, and K. Mandl, Surveillance Sans Fronti??res: Internet-Based Emerging Infectious Disease Intelligence and the HealthMap Project, PLoS Medicine, vol.2, issue.7, p.151, 2008.
DOI : 10.1371/journal.pmed.0050151.t001

J. Brownstein, C. Freifeld, and L. Madoff, Digital Disease Detection ??? Harnessing the Web for Public Health Surveillance, New England Journal of Medicine, vol.360, issue.21, pp.2153-2157, 2009.
DOI : 10.1056/NEJMp0900702

A. Signorini, A. Segre, and P. Polgreen, The Use of Twitter to Track Levels of Disease Activity and Public Concern in the U.S. during the Influenza A H1N1 Pandemic, PLoS ONE, vol.7, issue.2771, 2011.
DOI : 10.1371/journal.pone.0019467.g010

Y. Vandendijck, C. Faes, and N. Hens, Eight Years of the Great Influenza Survey to Monitor Influenza-Like Illness in Flanders, PLoS ONE, vol.63, issue.5
DOI : 10.1371/journal.pone.0064156.s001

S. Van-noort, M. Muehlen, R. De-andrade, H. Koppeschaar, C. et al., Gripenet: an internet-based system to monitor influenza-like illness uniformly across Europe, Euro Surveill, vol.12, pp.229-233, 2007.

N. Tilston, K. Eames, D. Paolotti, T. Ealden, and W. Edmunds, Internet-based surveillance of Influenza-like-illness in the UK during the 2009 H1N1 influenza pandemic, BMC Public Health, vol.339, issue.48, p.650, 2010.
DOI : 10.1136/bmj.b5213

M. Debin, C. Turbelin, T. Blanchon, I. Bonmarin, A. Falchi et al., Evaluating the Feasibility and Participants??? Representativeness of an Online Nationwide Surveillance System for Influenza in France, PLoS ONE, vol.8, issue.9, p.73675, 2013.
DOI : 10.1371/journal.pone.0073675.s001

. Invs, Institut de veille sanitaire

I. Friesema, C. Koppeschaar, G. Donker, F. Dijkstra, S. Van-noort et al., Internet-based monitoring of influenza-like illness in the general population: Experience of five influenza seasons in the Netherlands, Vaccine, vol.27, issue.45, pp.6353-6357, 2009.
DOI : 10.1016/j.vaccine.2009.05.042

. Eurostat, Distribution of households by household size

. Eurostat, Average household size

. Pordata, Base de dados Portugal contemporaneo: Resident population aged 15 to 64 and 65 and over: by highest level of educational qualifications obtained, pp.15-64

P. Tuppin, S. Choukroun, S. Samson, A. Weill, P. Ricordeau et al., Vaccination contre la grippe saisonni??re en France en 2010??et 2011??: diminution des taux de couverture et facteurs associ??s, La Presse M??dicale, vol.41, issue.11, pp.568-576, 2012.
DOI : 10.1016/j.lpm.2012.05.017

B. Nunes and M. Branco, Vacinação antigripal da população portuguesa: cobertura e algumas características do acto vacinal, Lisboa: Instituto Nacional de Saúde Dr. Ricardo Jorge. Departamento de Epidemiologia, 1010.

A. Sa-sousa, M. Morais-almeida, L. Azevedo, R. Carvalho, J. T. Todo-bom et al., Prevalence of asthma in Portugal - The Portuguese National Asthma Survey, Clinical and Translational Allergy, vol.2, issue.1, p.15
DOI : 10.1111/j.1398-9995.2007.01307.x

C. Simpson and A. Sheikh, Trends in the epidemiology of asthma in England: a national study of 333,294 patients, JRSM, vol.103, issue.3, pp.98-106, 2010.
DOI : 10.1258/jrsm.2009.090348

E. Eschwege, M. Charles, A. Basdevant, C. Moisan, G. Bonnélye et al., ObEpi Roche 2012 -Enquête épidémiologique nationale sur le surpoids et l'obésité

D. Balcan, V. Colizza, B. Goncalves, H. Hu, J. Ramasco et al., Multiscale mobility networks and the spatial spreading of infectious diseases, Proceedings of the National Academy of Sciences, vol.106, issue.51, pp.21484-21489, 2009.
DOI : 10.1073/pnas.0906910106

A. Barabasi and R. Albert, Emergence of scaling in random networks, Science, vol.286, pp.509-512, 1999.

M. Serrano, M. Boguna, and A. Vespignani, Extracting the multiscale backbone of complex weighted networks, Proceedings of the National Academy of Sciences, vol.106, issue.16, pp.6483-6488, 2009.
DOI : 10.1073/pnas.0808904106

C. Friedman, J. Wyatt, A. Smith, and B. Kaplan, Evaluation Methods in Medical Informatics, 1997.
DOI : 10.1007/978-1-4757-2685-5

S. Fox and L. Rainie, The online health care revolution: how the web helps Americans take better care of themselves, 2000.

I. Crespi and T. Miller, Family, Care and Work in Europe: An Issue of Gender, 2013.

M. Couper, Web Surveys, Public Opinion Quarterly, vol.64, issue.4, pp.464-494, 2000.
DOI : 10.1086/318641

S. Gosling, S. Vazire, S. Srivastava, and O. John, Should We Trust Web-Based Studies? A Comparative Analysis of Six Preconceptions About Internet Questionnaires., American Psychologist, vol.59, issue.2, pp.93-104, 2004.
DOI : 10.1037/0003-066X.59.2.93

J. Guthmann, L. Fonteneau, I. Bonmarin, and D. Levy-bruhl, Influenza vaccination coverage one year after the A(H1N1) influenza pandemic, pp.995-997, 2010.

M. Tizzoni, P. Bajardi, C. Poletto, J. Ramasco, D. Balcan et al., Real-time numerical forecast of global epidemic spreading: case study of 2009 A/H1N1pdm, BMC Medicine, vol.7, issue.1, p.165, 2012.
DOI : 10.1023/B:HCMS.0000020652.38181.da
URL : https://hal.archives-ouvertes.fr/inserm-00796005

J. Krosnick and L. Chang, A Comparison of Random Digit Dialing Telephone Survey Methodology with Internet Survey Methodology as Implemented by Knowledge Networks and Harris Interactive, The American Association for Public Opinion Research (AAPOR) 56th Annual Conference, 2001.

D. Dillman, G. Phelps, R. Tortora, K. Swift, J. Kohrell et al., Response rate and measurement differences in mixed-mode surveys using mail, telephone, interactive voice response (IVR) and the Internet, Social Science Research, vol.38, issue.1, pp.1-18, 2009.
DOI : 10.1016/j.ssresearch.2008.03.007