Seroprevalence and incidence of primary dengue infections among children in a rural region of Maharashtra, Western India.

BACKGROUND: Dengue infections have become a huge threat to public health systems in developing countries. Data on seroprevalence and incidence of dengue infections are lacking from rural regions of India. The objective of present study was to investigate the seroprevalence and incidence of dengue infection utilizing repeated serosurveys from a rural region of Maharashtra, Western India. METHODS: In the present study, 819 children between ages 5 to 15 years from 21 villages in Pune District of Maharashtra, India were sampled in 2014 and 2016. The sera were tested for the presence of dengue specific IgG using an indirect IgG ELISA kit. RESULTS: Overall seroprevalence of dengue was 15.3% (95% confidence intervals (CI) 12.9-17.8%) in 2014 and 20.5% (95% CI 17.8-23.4%) in 2016. Among the 694 children who were seronegative at baseline (2014), 78 seroconverted. Overall incidence rate of primary dengue was 54.2 infections/1000 children years (95% CI 43.0-67.3). Incidence of primary dengue infection was higher in children from urbanized villages compared to rural villages (Incidence rate ratio (IRR) 2.6 (95% CI 1.3-5.2)). In rural villages, incidence of primary dengue infection was higher in children aged 10 years or above as compared to those aged below 10 years (IRR 9.75 (95% CI 1.21-77.9). CONCLUSIONS: The study provides the incidence rates of primary dengue infections from a rural region of India. More multi centric studies investigating the incidence of dengue will provide accurate estimate of incidence of dengue and help formulate well directed policies. The results also suggest that urbanization and transitions in demographic settings might favour dengue outbreaks in rural regions and these regions need to be targeted for vector control measures.

Seroprevalence of rubella and immunogenicity following rubella vaccination in adolescent girls in India.

INTRODUCTION: Serologic surveys conducted in different countries indicate that rubella is a worldwide infection. Several such sero surveys conducted in India have also confirmed that 6-47% of women are susceptible to rubella infection. The current study was conducted on 1,329 female adolescents in 12 districts of Maharashtra, India, to assess their serological status in terms of rubella exposure. METHODOLOGY: After enrollment, a pre-vaccination blood sample was collected from the participants followed by rubella vaccination (R-vac). Adverse events were monitored for the next 6-8 weeks, at which time a post-vaccination sample was collected. RESULTS: Pre-vaccination rubella immunity was higher in the urban (80.2%) population compared to the rural (73.1%) population. Following R-vac vaccination, out of 1,159 participants who completed the study, all (100%) in the urban and 99.5% of participants in the rural area developed antibodies against rubella. CONCLUSION: Substantial numbers of women reach childbearing age without immunity against rubella and thus are at a risk of passing the infection to their fetuses, who can then develop subsequent congenital defects leading to congenital rubella syndrome (CRS). An immunization policy recommending vaccination with rubella or rubella containing vaccine is highly desirable to prevent rubella and CRS. 

Evolution, dispersal and replacement of American genotype dengue type 2 viruses in India (1956-2005): selection pressure and molecular clock analyses.

This study reports the phylogeny, selection pressure, genotype replacement and molecular clock analyses of many previously unstudied dengue type 2 virus (DENV-2) strains, isolated in India over a time span of almost 50 years (1956-2005). Analysis of complete envelope (E) gene sequences of 37 strains of DENV-2 from India, together with globally representative strains, revealed that the American genotype, which circulated predominantly in India during the pre-1971 period, was then replaced by the Cosmopolitan genotype. Two previously unreported amino acid residues, one in the American (402I) and one in the Cosmopolitan (126K) genotypes, known to be involved functionally in the cellular tropism of the virus, were shown to be under positive selection pressure. The rate of nucleotide substitution estimated for DENV-2 was 6.5x10(-4) substitutions per site year(-1), which is comparable with earlier estimates. The time to the most recent common ancestor of the pre-1971 Indian strains and the American genotype was estimated to be between 73 and 100 years (1905-1932), which correlates with the historical record of traffic between India and South America and suggests transportation of the virus from the Americas. Post-1971 Indian isolates formed a separate subclade within the Cosmopolitan genotype. The estimated time to the most recent common ancestor of the Indian Cosmopolitan strains was about 47 years, with further estimates indicating the migration of DENV-2 from India to countries across the Indian ocean between 1955 and 1966. Overall, the present study increases our understanding of the events leading to the establishment and dispersal of the two genotypes in India.