BackgroundHuman respiratory syncytial virus (HRSV) is the most important virus causing lower respiratory infection in young children. The complete genetic characterization of RSV clinical strains is a prerequisite for understanding HRSV infection in the clinical context. Current information about the genetic structure of the HRSV genome has largely been obtained using tissue culture adapted viruses. During tissue culture adaptation genetic changes can be introduced into the virus genome, which may obscure subtle variations in the genetic structure of different RSV strains.MethodsIn this study we describe a novel Sanger sequencing strategy which allowed the complete genetic characterisation of 14 clinical HRSV strains. The viruses were sequenced directly in the nasal washes of severely hospitalized children, and without prior passage of the viruses in tissue culture.ResultsThe analysis of nucleotide sequences suggested that vRNA length is a variable factor among primary strains, while the phylogenetic analysis suggests selective pressure for change. The G gene showed the greatest sequence variation (2-6.4%), while small hydrophobic protein and matrix genes were completely conserved across all clinical strains studied. A number of sequence changes in the F, L, M2-1 and M2-2 genes were observed that have not been described in laboratory isolates. The gene junction regions showed more sequence variability, and in particular the intergenic regions showed a highest level of sequence variation. Although the clinical strains grew slower than the HRSVA2 virus isolate in tissue culture, the HRSVA2 isolate and clinical strains formed similar virus structures such as virus filaments and inclusion bodies in infected cells; supporting the clinical relevance of these virus structures.ConclusionThis is the first report to describe the complete genetic characterization of HRSV clinical strains that have been sequenced directly from clinical material. The presence of novel substitutions and deletions in the vRNA of clinical strains emphasize the importance of genomic characterization of non-tissue culture adapted primary strains.

Background: This study was designed to find out a relationship of dengue infection with climatic factors such as rainfall, temperature and relative humidity during the dengue fever epidemic in the year 2003. Blood samples were collected from 1550 patients experiencing a febrile illness clinically consistent with dengue infection. Serological confirmation of Dengue Infection was done using Dengue Duo IgM and IgG Rapid Strip test (Pan Bio, Australia), which detected dengue-specific antibodies. Monthly data of total rainfall, temperature and relative humidity for the year 2003 was obtained from Meteorological Department of Delhi, New Delhi and retrospectively analyzed.

The recognition of DF (DHF Dengue Hemorrhagic Fever) is very complicated due to occurrence of a wide spectrum of clinical signs and symptoms during acute phase of illness. Moreover, presence of four serotypes further complicates the prognosis. To investigate the predictors of disease severity and elucidate the prognostic markers among four dengue serotypes, this study was conducted on 320 inpatients having acute febrile illness clinically suspected as DI, over a period of five years. Dengue serotypes were confirmed by multiplex reverse transcriptase (RT)-PCR. Eighty patients were positive for DI with presence of Den-1, Den-2, Den-3, and Den-4 in 8, 35, 27 and 10 patients, respectively. The severe clinical manifestations, abdominal pain and hepatomegaly, were comparatively higher in Den-2 patients. Liver aminotransferases levels were also higher in Den-2 patients (app. 5 fold). This study clearly indicates the hyperendemicity of all dengue serotypes. Nucleotide sequencing of Envelope region revealed that the presently emerged Den-3 belongs to type III, having high homology with genotype responsible for number of outbreaks in 1980s. The re-emergence of this deadly type can be suspected to cause more outbreaks in future and is a matter of great concern.

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The recognition of DF (DHF Dengue Hemorrhagic Fever) is very complicated due to occurrence of a wide spectrum of clinical signs and symptoms during acute phase of illness. Moreover, presence of four serotypes further complicates the prognosis. To investigate the predictors of disease severity and elucidate the prognostic markers among four dengue serotypes, this study was conducted on 320 inpatients having acute febrile illness clinically suspected as DI, over a period of fi ve years. Dengue serotypes were confi rmed by multiplex reverse transcriptase (RT)-PCR. Eighty patients were positive for DI with presence of Den-1, Den-2, Den-3, and Den-4 in 8, 35, 27 and 10 patients, respectively. The severe clinical manifestations, abdominal pain and hepatomegaly, were comparatively higher in Den-2 patients. Liver aminotransferases levels were also higher in Den-2 patients (app. 5 fold). This study clearly indicates the hyperendemicity of all dengue serotypes. Nucleotide sequencing of Envelope region revealed that the presently emerged Den-3 belongs to type III, having high homology with genotype responsible for number of outbreaks in 1980s. The re-emergence of this deadly type can be suspected to cause more outbreaks in future and is a matter of great concern.