Molecular characterization of influenza viruses collected from young children in Uberlandia, Brazil - from 2001 to 2010.

BACKGROUND: Influenza remains a major health problem due to the seasonal epidemics that occur every year caused by the emergence of new influenza virus strains. Hemagglutinin (HA) and neuraminidase (NA) glycoproteins are under selective pressure and subjected to frequent changes by antigenic drift. Therefore, our main objective was to investigate the influenza cases in Uberlândia city, Midwestern Brazil, in order to monitor the appearance of new viral strains, despite the availability of a prophylactic vaccine. METHODS: Nasopharyngeal samples were collected from 605 children less than five years of age presenting with acute respiratory disease and tested by immunofluorescence assay (IFA) for detection of adenovirus, respiratory syncytial virus, parainfluenza virus types 1, 2, and 3 and influenza virus types A and B. A reverse transcription-PCR (RT-PCR) for influenza viruses A and B was carried out to amplify partial segments of the HA and NA genes. The nucleotide sequences were analyzed and compared with sequences of the virus strains of the vaccine available in the same year of sample collection. RESULTS: Forty samples (6.6%) were tested positive for influenza virus by IFA and RT-PCR, with 39 samples containing virus of type A and one of type B. By RT-PCR, the type A viruses were further characterized in subtypes H3N2, H1N2 and H1N1 (41.0%, 17.9%, and 2.6%, respectively). Deduced amino acid sequence analysis of the partial hemagglutinin sequence compared to sequences from vaccine strains, revealed that all strains found in Uberlândia had variations in the antigenic sites. The sequences of the receptor binding sites were preserved, although substitutions with similar amino acids were observed in few cases. The neuraminidase sequences did not show significant changes. All the H3 isolates detected in the 2001-2003 period had drifted from vaccine strain, unlike the isolates of the 2004-2007 period. CONCLUSIONS: These results suggest that the seasonal influenza vaccine effectiveness could be reduced because of A H3N2 variants that circulated in 2001-2003 years. Thus, an early monitoring of variants circulating in the country or in a region may provide important information about the probable efficacy of the vaccine that will be administered in an influenza season.

Respiratory virus infections in hospitalized and non-hospitalized children: determinants of severe course of the disease.

INTRODUCTION: Viral respiratory disease constitutes a great burden worldwide mainly among children. OBJECTIVE: One pursued to compare disease characteristics of children who required hospitalization from those who did not require hospitalization due to a viral respiratory disease. METHODOLOGY: Medical and demographic data were collected through questionnaires and nasopharyngeal aspirates were tested for detection of respiratory disease viruses of in and outpatients up to five years old, presenting acute respiratory infection. RESULTS: Respiratory syncytial virus predominated among hospitalized children while other viruses (Human rhinovirus, Influenza virus, Parainfluenza virus, Adenovirus, and Human metapneumovirus) together predominated among non-hospitalized patients. Although children with underlying risk condition required longer hospitalization, previously healthy children presented severe disease and required hospitalization as well. Also, clinical characteristics were not found that may distinguish RSV infected children who had comorbidities from those previously healthy. CONCLUSIONS: Children who were hospitalized due to respiratory distress had well defined characteristics: early age, respiratory syncytial virus infection, bronchiolitis and presence of comorbidity. Nevertheless, rapid respiratory syncytial virus identification among early age children may be of great value in order to avoid medical misconduct, such as unnecessary antibiotic prescription and preventive health care before an eventual clinical worsening encompassing previous health status.