Clinical characteristics of adult patients with influenza-like illness hospitalized in general ward during Influenza A H1N1 pandemic 2009/2010

OBJECTIVE: To investigate clinical and laboratory features of patients with Influenza A H1N1 virus infection hospitalized during 2009/2010 pandemic. METHODS: Prospective observational study comparing clinical and laboratory characteristics of Influenza A H1N1 positive and negative patients with influenza-like illness (ILI). RESULTS: From October 21, 2009 to February 14, 2010 196 ILI patients were admitted, of which 66 tested positive for Influenza A H1N1. The patients with H1N1 infection were younger (43 years vs. 65 years; P < 0.01), more patients were pregnant (P < 0.01), had allergies (P < 0.05) or, asthma (P < 0.01). H1N1 positive patients were more often febrile (91% vs. 72.9%; P < 0.01) and had a higher prevalence of headache (31.8% vs. 18.5%; P < 0.05). Lower values of C-reactive protein (88 pg/dl vs. 126 pg/dl; P < 0.01), procalcitonine (0.42 A mu g/l vs. 3.98 A mu g/l; P < 0.05), leukocyte count (7.4*10(9)/l vs. 11.7*10(9)/l; P < 0.01) and higher values of troponin (0.162 A mu/l vs. 0.146 A mu g/l; P < 0.01) were found in H1N1 positive patients. More bacterial infections were found in H1N1 negative group (68.8% vs. 89.2%; P < 0.05). CONCLUSIONS: In this study patients infected with Influenza A H1N1 differed from H1N1 negative ILI patients in several clinical and laboratory characteristics. The same was observed also by other investigators. The results of the study suggest some other specific features, such as a higher incidence of headache and higher values of troponin in Influenza A H1N1 infected patients.