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Striking similarities in the presentation and duration of illness of influenza A and B in the community: a study based on sentinel surveillance networks in France and Turkey, 2010-2012.

Cohen, J.M., Silva, M.L., Caini, S., Ciblak, M.A., Mosnier, A., Daviaud, I., Matias, G., Badur, S., Valette, M., Enouf, V., Paget, J., Fleming, D.M. Striking similarities in the presentation and duration of illness of influenza A and B in the community: a study based on sentinel surveillance networks in France and Turkey, 2010-2012. PLoS One: 2015, 10(10), e0139431
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Influenza B represents a high proportion of influenza cases in some seasons (even over 50%).

Aim
The Influenza B study in General Practice (IBGP) is a multicenter study providing information about the clinical, demographic and socio-economic characteristics of patients affected by lab-confirmed influenza A or B.

Method
Influenza B patients and age-matched influenza A patients were recruited within the sentinel surveillance networks of France and Turkey in 2010-11 and 2011-12 seasons. Data were collected for each patient at the swab test day, after 9 ± 2 days and, if not recovered, after 28 ± 5 days. It was related to patient's characteristics, symptoms at presentation, vaccination status, prescriptions of antibiotics and antivirals, duration of illness, follow-up consultations in general practice or emergency room. We performed descriptive analyses and developed a multiple regression model to investigate the effect of patients and disease characteristics on the duration of illness. Overall, 774 influenza cases were included in the study: 419 influenza B cases (209 in France and 210 in Turkey) and 355 influenza A cases (205 in France and 150 in Turkey).

Results
There were no differences between influenza A and B patients in terms of clinical presentation and number of consultations with a practitioner; however, the use of antivirals was higher among influenza B patients in both countries. The average (median) reported duration of illness in the age groups 0-14 years, 15-64 years and 65+ years was 7.4 (6), 8.7 (8) and 10.5 (9) days in France, and 6.3 (6), 8.2 (7) and 9.2 (6) days in Turkey; it increased with age but did not differ by virus type; increased duration of illness was associated with antibiotics prescription. In conclusion, our findings show that influenza B infection appears not to be milder disease than influenza A infection.