CLINICAL AND EPIDEMIOLOGICAL CHARACTERIZATION OF INFLUENZA A/H1N1PDM AND B AMONG HOSPITALIZED CHILDREN, GEORGIA, SEASON 2010-2011.

The aim of the study was to describe, analyze and compare clinical and epidemiological characteristics of laboratory confirmed influenza A(H1N1)pdm and B cases in hospitalized children during post pandemic season. Between 1st January and 1st May, 2011 retrospective observational study was conducted in M. Iashvili Children's Central Hospital. From 1028 patients with influenza like illness hospitalized at Children's Hospital 871 specimens were collected and 360 tested positive for influenza: A(H1N1)pdm - 139 and B - 221. Data were obtained for 290 cases: A(H1N1)pdm - 122 and B - 168. At the time of hospital admission, influenza A(H1N1)pdm and B cases had similar median age of 2 years. The median length of hospital stay was 5 days for both influenza types. Predominant clinical symptoms were fever (98.3%), cough (82.4%) and running nose (68.6%). 39.7% (115/290) of patients suffered with lower respiratory tract infection: A(H1N1)pdm - 41% (50/122) and B - 38.7% (65/168). 19% (55/290) developed pneumonia of which 12 with primary diagnosis of acute respiratory failure were admitted to ICU: A(H1N1)pdm - 4.9% (6/122) and B - 3.6% (6/168). Median length in ICU stay was 6 days. Only two patients with A(H1N1)pdm required artificial ventilation with one fatal outcome. Almost equally (31%) patients with influenza A or B viruses suffered with at least one pre-existing condition. Statistically significant association was revealed between neurological pre-existing conditions and developing pneumonia (OR=5.6; p=0.00) and ICU requirement (OR=17.5, p=0.00). Congenital malformations were also associated with sever course of disease (OR=9.1; p=0.01). Treatment with antiviral oseltamivir was prescribed to 29.5% (36/122) A(H1N1)pdm and 8.3% (14/168) B cases among whom only 24% cases received antiviral within 48 hours after symptoms onset. None of the patients was vaccinated against influenza. Our study revealed no significant difference between influenza A(H1N1)pdm and influenza B in terms of age distribution, clinical manifestation, hospital stay or complications in hospitalized children during post pandemic season. Pre-existing conditions such as neurological disorders and congenital malformations represented risk factors for severe course of influenza, therefore timely antiviral treatment and annual influenza vaccination is recommended to avoid complications.