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Journal ArticleDOI

Epidemiological and demographic characteristics of dengue at a tertiary care centre in Gujarat.

01 Oct 2017-Journal of Vector Borne Diseases (Medknow Publications)-Vol. 54, Iss: 4, pp 375-376
TL;DR: The results revealed that no patient was admitted with dengue haemorrhagic fever (DHF) or shock syndrome (DSS) either in Rajkot SSH or other seven Saurashtra hospitals, although suspected d Dengue patients in Saurashtra districts constituted 69.61% (4366/6272) of national average; but NVBDCP’s record showed 15 such patients died from the denge virus infection in districts of Gujarat.
Abstract: The work on epidemiological and demographic characteristics of dengue at a tertiary care centre in Saurashtra region by Mistry et al1 during the year 2013, is timely and useful from the surveillance point of view and appears very much relevant for dengue containment programmes. The epidemiological records by the National Vector Borne Disease Control Programme (NVBDCP), India for dengue cases and deaths in Gujarat was a matter of great concern in comparison to other states of India2. The authors reported that the total number of hospitalbased suspected cases attending tertiary care OPD with dengue viral (DENV) infection during January 1 to December 31, 2013 was 4366, but as per NVBDCP record, the total number of suspected dengue cases and deaths in the state of Gujarat in 2013 was 6272 and 15, respectively (spread over different parts of the state including other seven Saurashtra districts, i.e. Kutch, Surendranagar, Jamnagar, Bhavnagar, Porbandar, Amreli, and Junagarh), and this was not incorporated while reconciling the work. Also, the reported district-wise percentages of suspected dengue cases were very much inconsistent with national level data (as reported by NVBDCP 2016)2.Besides, in Fig. 2, the percentage of dengue cases shown was 43.5% which was different from 61.8% mentioned in the text which is very much confusing. Percentage-wise, there was high discrepancy in reported cases of dengue from the Sentinel Surveillance Hospital (SSH) OPDs, for example, Rajkot district reported 2563 cases while other seven Saurashtra districts showed 1803 cases with respect to the total cases of 6272 reported by NVBDCP. It indicates that the rest dengue cases (only 1906) were spread over to the remaining districts of Gujarat which includes 24 SSH OPDs, out of total 32. The authors may disclose such inconsistencies of epidemiological data from the surveillance point of view. The results revealed that no patient was admitted with dengue haemorrhagic fever (DHF) or shock syndrome (DSS) either in Rajkot SSH or other seven Saurashtra hospitals, although suspected dengue patients in Saurashtra districts constituted 69.61% (4366/6272) of national average; but NVBDCP’s record showed 15 such patients died from the dengue virus infection in districts of Gujarat. The authors may describe such surveillance incongruities, when they mention about developing capacity building in primary health centres (PHCs) level in the study area. In the article, Mistry et al1 mentioned reducing density of vector breeding sites in selected foci of dengue positive cases in residential areas, i.e. both in urban (76.2%) and rural (23.8%) settings of the Saurashtra districts,but it has not been undertaken in selected epidemic sites with reports of any nearby critically ill patients, i.e. DHS or DSS, attended OPD(s), nor shown in the text, as it is one of the primary and principal measures of point-of-care hospital-based capacity building. The authors may refer such integrated approach to achieve study objectives. Since the primary vector of dengue in India is Aedes aegypti3, an entomological and demographic investigation of larval density in and around the endemic foci of study sites of Saurashtra districts was essential to explore correlating demographic characteristics for containment purposes. Further, the recent epidemiological data on dengue, revealed the existence of repeated transmission cycles in greater way and culminated an out-burst of vector densities with the presence of primary vector Ae. aegypti in the area. Since, Gujarat is an ideal state for autochthonous dengue cases, originating from the irregular settlements outside the urban perimeters with a recent record of viral lineages characteristics of the circulation of strains, poor sanitation with higher infestation levels, accidental transport of working class people in numerous construction project sites, easy dispersion distances of mosquitoes vis-à-vis their contacts to human-being for co-circulating dengue lineages (15–800 m), overwarming and cold waves with cryptic maintenance of viral strains (transovarian transmission–TOT) for >3–4 months favour studCorrespondence
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Journal Article
TL;DR: It was pertinent to assess the aetiology of inter-epidemic periods and the relative importance of intrinsic and extrinsic influences which has not been done in climate predictive early warning model.
Abstract: Sir, The article by Karim et al1 on climatic factors influencing dengue cases in Dhaka city, a model for dengue prediction is timely, and has dealt with a conceptual framework for constructing and evaluating climate-based Early Warning System (EWS). In 2004, the World Health Organization2 prepared guidelines for the Department of Communicable Diseases Surveillance and Response (CSR), Department of Protection of Human Environment (PHE) and the Roll Back Malaria to predict infectious diseases wherein a few salient features were identified, namely (i) strengthening long-term disease surveillance system for timely model development, (ii) utilizing relevant criteria and technology for evaluating model accuracy, (iii) interpretation of non-climatic factors, and (iv) an access to help policy makers for a particular need and response decision. The author1 have developed three models for data analysis, model development and validation where independence of data point was checked through Durbin-Watson estimate but choosing monthly rainfall (mm), humidity (%), and temperature (°C) (minimum and maximum) as independent variables with monthly dengue cases as dependent variable. They could have considered other monthly vector indices also, viz. vector density, their extrinsic incubation period and gonotropic cycle length along with other three climate parameters as independent variables. Weather-driven transmission dynamics and its assessment is related to two important insights central to the development of mathematical dengue epidemiology3, (i) the mass action potential: dependent rate contact between susceptible host and infectious vectors and (ii) threshold theory that limits vectors exceeding certain critical level for the transmission to occur. It has been reported that these insights established two weather-driven models (Container-inhabiting mosquito simulation model CIMSiM and Dengue simulation model DENSiM) used to elucidate non-linear relationship influencing activity in dengue system which have not been considered while developing the models by the present authors. In discussion only the role of multiple serotypes, immune-mediated serotype interactions and environmental variations has been mentioned, but none of the parameters for studying vectors have been discussed for the period extending 2000-2009. The aetiology of antibody-dependent negative and positive strain interactions during the inter-epidemic periods of 0-5 years has not been corroborated with age-stratified seropositive data in which the force of infection was reported to vary over a 3-4 year period4. Further, two possible causes of between-year epidemic events have been reported, (i) extrinsic- EI Nino phase of Southern Oscillation (ENSO) type5 climate phenomenon and, (ii) intrinsic-associated with host-pathogen dynamics. At this point of assessment, it was pertinent to assess the aetiology of inter-epidemic periods and the relative importance of intrinsic and extrinsic influences which has not been done in climate predictive early warning model. This situation also persisted in 2003 and relevant parameters were not taken into consideration to understand the status of infectious vectors and susceptible host in such urban settings. In this study1, the dengue case data have been collected from the hospitals for analysis for model development but to validate their basic indices, serotyping was essential. During the 9-year study period, 22,705 dengue cases were passively recorded without clinical diagnosis. Global Surveillance on dengue and DHF in WHO-managed Dengue- Net collects and analyse case data from participating countries/partner. In a climatic prediction model the possible of DHF and DSS cases, if any is essential to asses the disease burden vis-a-vis emergency preparedness predictive to identify serotype prevalence (acquired elsewhere) in climate prediction model. Bangladesh is a close neighbour to other South-East Asian countries namely India, Myanmar and Thailand where migration is a regular feature of local habitats in bordering countries. The basic demography of patients during a 9-year period suffering from dengue infestation could have been identified the particular area(s)/location(s), age-specific stratification, role of specific vectors (i.e. Aedes aegypti) and their development. Survival rates of vectors are basically the functions of temperature and atmospheric moisture (saturation deficit) usually used to interpret certain weather-driven ENSO influences5, a factor enhances dengue cases in Dhaka City. This has been mentioned here because humidity has a significant role of increasing the trend of dengue outbreaks two months prior to outbreak and two months ahead of that. In retrospective model validation, the result showed that in 2003 the predicted and observed number were not correlated significantly, because the cases were less. The demography of the area-specific vector indices with serotyping of person infected in previous two years i.e. 2001 and 2002 and similarly after two years it was essential to understand DENV viral propagation in a spatio-temporal phylogeny mode6. This would have disclosed the viral propagation, introduction time, evolution pattern in densely populated urban settings of Dhaka city. The authors have cited studies from India and Thailand but certain field-based pilot experiments with vectors and serotyping in endemic area were essential to correlate these appropriately to reflect the area specific prevalence of weather-driven incidences as pointed out in the discussion. Of the three retrospective models, only model 3 showed 61 per cent variations in case occurrences with significant correlation observed with the predicted and the observed number in only three years, i.e., 2001, 2005 and 2008, but not in other 5 years except 2003 for which an explanation is required. In such a situation, time-series techniques of spectral density analysis (SDA) would have been used to correlate their periodicity in both the epidemiological and meteorological data (ENSO) after availing the vector indices3. While making use of the SDA model between the years epidemic events, extrinsics associated with ENSO-type climate phenomenon and intrinsics associated with host pathogen population dynamics could have been made possible. In this situation, it is essential to assess the aetiology of inter-epidemic periods and the importance of intrinsic and extrinsic influences to develop an EWS for disease epidemics, because there is a dynamic interaction between host and parasite/pathogen populations. In epidemiological in Susceptible, Exposed, Infections, Recorded (SEIR) unforced models of directly transmitted diseases are predicted to exhibit damped oscillations with an appropriate inter-epidemic periods. It has also been reported4 that inter-epidemic period is determined by climate conditions at least for the vector-borne diseases where intrinsic population dynamic processes offer most parsimonious explanation of dengue incidences where epidemiological models combining within-year extrinsic and between-year intrinsic determinants of mosquito-borne disease incidence for epidemic prediction should be an amenable platform of climate-based incidence prediction.

1 citations

References
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Journal ArticleDOI
TL;DR: Estimated transmission thresholds for dengue based on an easily-derived statistic, the standing crop of Aedes aegypti pupae per person in the environment are developed and targets for the actual degree of suppression required to prevent or eliminate transmission in source reduction programs are provided.
Abstract: The expense and ineffectiveness of drift-based insecticide aerosols to control dengue epidemics has led to suppression strategies based on eliminating larval breeding sites. With the notable but short-lived exceptions of Cuba and Singapore, these source reduction efforts have met with little documented success; failure has chiefly been attributed to inadequate participation of the communities involved. The present work attempts to estimate transmission thresholds for dengue based on an easily-derived statistic, the standing crop of Aedes aegypti pupae per person in the environment. We have developed these thresholds for use in the assessment of risk of transmission and to provide targets for the actual degree of suppression required to prevent or eliminate transmission in source reduction programs. The notion of thresholds is based on 2 concepts: the mass action principal-the course of an epidemic is dependent on the rate of contact between susceptible hosts and infectious vectors, and threshold theory-the introduction of a few infectious individuals into a community of susceptible individuals will not give rise to an outbreak unless the density of vectors exceeds a certain critical level. We use validated transmission models to estimate thresholds as a function of levels of pre-existing antibody levels in human populations, ambient air temperatures, and size and frequency of viral introduction. Threshold levels were estimated to range between about 0.5 and 1.5 Ae. aegypti pupae per person for ambient air temperatures of 28 degrees C and initial seroprevalences ranging between 0% to 67%. Surprisingly, the size of the viral introduction used in these studies, ranging between 1 and 12 infectious individuals per year, was not seen to significantly influence the magnitude of the threshold. From a control perspective, these results are not particularly encouraging. The ratio of Ae. aegypti pupae to human density has been observed in limited field studies to range between 0.3 and >60 in 25 sites in dengue-endemic or dengue-susceptible areas in the Caribbean, Central America, and Southeast Asia. If, for purposes of illustration, we assume an initial seroprevalence of 33%, the degree of suppression required to essentially eliminate the possibility of summertime transmission in Puerto Rico, Honduras, and Bangkok, Thailand was estimated to range between 10% and 83%; however in Mexico and Trinidad, reductions of >90% would be required. A clearer picture of the actual magnitude of the reductions required to eliminate the threat of transmission is provided by the ratio of the observed standing crop of Ae. aegypti pupae per person and the threshold. For example, in a site in Mayaguez, Puerto Rico, the ratio of observed and threshold was 1.7, meaning roughly that about 7 of every 17 breeding containers would have to be eliminated. For Reynosa, Mexico, with a ratio of approximately 10, 9 of every 10 containers would have to be eliminated. For sites in Trinidad with ratios averaging approximately 25, the elimination of 24 of every 25 would be required. With the exceptions of Cuba and Singapore, no published reports of sustained source reduction efforts have achieved anything near these levels of reductions in breeding containers. Practical advice on the use of thresholds is provided for operational control projects.

386 citations

Journal ArticleDOI
TL;DR: This is the largest such outbreak reported from India, indicating a serious resurgence of dengue virus infection.
Abstract: India An outbreak of dengue hemorrhagic fever/dengue shock syndrome (DHS/DSS) occurred in 1996 in India in and near Delhi. The cause was confirmed as dengue virus type 2, by virus cultivation and indirect immunofluorescence with type-specific monoclonal antibodies. This is the largest such outbreak reported from India, indicating a serious resurgence of dengue virus infection.

170 citations

Journal ArticleDOI
TL;DR: The use of both geographic and temporally structured phylogenetic data provided a detailed view on the spread of at least two dengue viral strains in a populated urban area and may shed light on DENV circulation.
Abstract: The dengue virus has a single-stranded positive-sense RNA genome of approximately 10.700 nucleotides with a single open reading frame that encodes three structural (C, prM, and E) and seven nonstructural (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) proteins. It possesses four antigenically distinct serotypes (DENV 1-4). Many phylogenetic studies address particularities of the different serotypes using convenience samples that are not conducive to a spatio-temporal analysis in a single urban setting. We describe the pattern of spread of distinct lineages of DENV-3 circulating in Sao Jose do Rio Preto, Brazil, during 2006. Blood samples from patients presenting dengue-like symptoms were collected for DENV testing. We performed M-N-PCR using primers based on NS5 for virus detection and identification. The fragments were purified from PCR mixtures and sequenced. The positive dengue cases were geo-coded. To type the sequenced samples, 52 reference sequences were aligned. The dataset generated was used for iterative phylogenetic reconstruction with the maximum likelihood criterion. The best demographic model, the rate of growth, rate of evolutionary change, and Time to Most Recent Common Ancestor (TMRCA) were estimated. The basic reproductive rate during the epidemics was estimated. We obtained sequences from 82 patients among 174 blood samples. We were able to geo-code 46 sequences. The alignment generated a 399-nucleotide-long dataset with 134 taxa. The phylogenetic analysis indicated that all samples were of DENV-3 and related to strains circulating on the isle of Martinique in 2000-2001. Sixty DENV-3 from Sao Jose do Rio Preto formed a monophyletic group (lineage 1), closely related to the remaining 22 isolates (lineage 2). We assumed that these lineages appeared before 2006 in different occasions. By transforming the inferred exponential growth rates into the basic reproductive rate, we obtained values for lineage 1 of R(0) = 1.53 and values for lineage 2 of R(0) = 1.13. Under the exponential model, TMRCA of lineage 1 dated 1 year and lineage 2 dated 3.4 years before the last sampling. The possibility of inferring the spatio-temporal dynamics from genetic data has been generally little explored, and it may shed light on DENV circulation. The use of both geographic and temporally structured phylogenetic data provided a detailed view on the spread of at least two dengue viral strains in a populated urban area.

60 citations


Additional excerpts

  • ...J Vector Borne Dis 2015; 52(4): 299–303....

    [...]

Journal Article
TL;DR: A long term serosurveillance study may help to provide more information about the intensity, seasonal incidence and seasonal effect of dengue virus infection in Gujarat state, India.
Abstract: Background & objectives Dengue is one of the most important vector-borne viral infection which may lead to haemorrhage or even shock. The present study was conducted with an objective to study the epidemiological and demographic characteristics of dengue disease during the year 2013 in Saurashtra region of Gujarat state, India. Methods A longitudinal study was conducted at sentinel surveillance centre for dengue disease at microbiology department of tertiary care hospital in Rajkot, Gujarat from 1 January 2013 to 31 December 2013. A total of 4366 blood samples were collected during study period and serologically tested for dengue NS1 antigen and IgM antibody by capture ELISA testing from various districts of Saurashtra region. Patients with acute onset of illness, high grade fever, severe headache, backache, musculoskeletal pain or retro-bulbar pain with or without rashes were considered as clinically suspected case of dengue virus infection. Patient who presented with fever and found positive for Dengue NS1 Ag and/or IgM Ab was considered as a case. A pre-tested structured proforma was used as a tool for data collection. The data was entered into EpiInfo software and analyzed by using appropriate statistical test (chi-square test). Results Out of 4366 tested samples, 41.3% samples were found positive for dengue. Majority of samples were tested in age group 16-25 yr (33.9%) and 26-45 yr (31.1%). The ratio of male cases (60.8%) was higher than female cases. Two-third (68.7%) suspected cases were residing in urban areas of Saurashtra region. More than half of the cases (57%) were diagnosed within five days of fever by NS1 antigen test. The reporting of number of cases increased from July 2013, which reached to peak during September 2013 followed by decrease till December 2013. Interpretation & conclusion Dengue predominately affected males and urban population. A seasonal occurrence was reported mainly during monsoon season. A long term serosurveillance study may help to provide more information about the intensity, seasonal incidence and seasonal effect.

16 citations

Journal ArticleDOI
10 Jan 2011
TL;DR: The hypothesis of an impact of both the regional and local contexts on the genetic evolution of dengue viruses is supported.
Abstract: During the last decades, whole chains of dengue epidemics emerged in the South Pacific region. In contrast with the situation in hyper endemic continental countries and in the Caribbean, the epidemiology of dengue in the South Pacific islands Countries (SPICs) is characterized by the non-persistent co-circulation of multiple serotypes and the long-term predominance, with local re-emergences, of a single genotype. Local specificities in the epidemiological profile of dengue can also been observed between the SPICs, probably related to differences in the geographical situation, the eco-biological context (climate, endemic mosquito species), the demography and the population flew. In the present study, by focusing on the past DEN31989-96 and the recent DEN12001-10 and DEN42007-10 circulation periods, we addressed the question of the circulation of dengue viruses between the French Pacific Territories and the impact of the “local context” on viral genetic evolution. Hundreds of viral strains collected during both epidemic and endemic periods in French Polynesia (FP), New Caledonia (NC) and Wallis & Futuna (WF) were sequenced on the complete E gene. The phylogenetic analysis corroborates the previous observations on the predominant circulation of a single genotype. Within each serotype/genotype, the viral strains collected in the SPICs formed a “Pacific clade”. Within this clade, the strains from the French Pacific Territories formed a unique lineage during the early epidemic/endemic circulation periods but diverged in distinct lineages when the virus re-emerged. By analyzing the in time/in space fixations of genetic mutations on the E gene, we observed that some mutations are shared by the French Pacific Territories but differ from the other SPICs. Moreover, although the majority of the mutations acquired in FP are also found on NC and WF strains, some seem to be specific to the Territory. Our results support the hypothesis of an impact of both the regional and local contexts on the genetic evolution of dengue viruses.

3 citations