Joint Involvement Can Predict Chikungunya in a Dengue Syndemic Setting in India.

Dengue and chikungunya have been endemic in India but have the tendency to cause periodic epidemics, often together, wherein they are termed 'syndemic'. Such a syndemic was observed in 2016 in India which resulted in a further scarcity of already resource-poor specific diagnostic infrastructure even in many urban conglomerates. A cross-sectional study was thus conducted, on 978 fever patients that consulted the ICMR-NIMR fever clinic, New Delhi, in September 2016, with an objective to identify symptom/s that could predict chikungunya with certainty. The overall aim was to rationally channelize the most clinically suitable patients for the required specific diagnosis of chikungunya. Based on their clinical profile, febrile patients attending NIMR's clinic, appropriate laboratory tests and their association analyses were performed. Bivariate analysis on 34 clinical parameters revealed that joint pain, joint swelling, rashes, red spots, weakness, itching, loss of taste, red eyes, and bleeding gums were found to be statistically significantly associated predictors of chikungunya as compared to dengue. While, in multivariate analysis, only four symptoms (joint pain in elbows, joint swelling, itching and bleeding gums) were found in statistically significant association with chikungunya. Hence, based on the results, a clinician may preferably channelize febrile patients with one or more of these four symptoms for chikungunya-specific diagnosis and divert the rest for dengue lab diagnosis in a dengue-chikungunya syndemic setting.

Comparative Assessment of Diagnostic Performance of Cytochrome Oxidase Multiplex PCR and 18S rRNA Nested PCR.

Malaria elimination and control require prompt and accurate diagnosis for treatment plan. Since microscopy and rapid diagnostic test (RDT) are not sensitive particularly for diagnosing low parasitemia, highly sensitive diagnostic tools are required for accurate treatment. Molecular diagnosis of malaria is commonly carried out by nested polymerase chain reaction (PCR) targeting 18S rRNA gene, while this technique involves long turnaround time and multiple steps leading to false positive results. To overcome these drawbacks, we compared highly sensitive cytochrome oxidase gene-based single-step multiplex reaction with 18S rRNA nested PCR. Cytochrome oxidase (cox) genes of P. falciparum (cox-III) and P. vivax (cox-I) were compared with 18S rRNA gene nested PCR and microscopy. Cox gene multiplex PCR was found to be highly specific and sensitive, enhancing the detection limit of mixed infections. Cox gene multiplex PCR showed a sensitivity of 100% and a specificity of 97%. This approach can be used as an alternative diagnostic method as it offers higher diagnostic performance and is amenable to high throughput scaling up for a larger sample size at low cost.

Magnetic Multiplex Loop Mediated Isothermal Amplification (MM-LAMP) technique for simultaneous detection of dengue and chikungunya virus.

Dengue and chikungunya viruses are arthropod borne virus spread through common vector instigating infection in human. There has been an increased recognition that more attention needs to be paid to similar sympotoms caused by both of the virus as they spread in the same region at same time. It warrants need of cost effective, user friendly and rapid multiplex diagnostic technique which could simultaneously diagnose and identify between two virus diseases in resource poor setting. A magnetic multiplex loop mediated isothermal amplification (MM-LAMP) technique was developed by coupling multiplex LAMP with magnetic particle-based naked eye visualization to overcome the shortcoming of simultaneous detection of both diseases. In recent years this technology has emerged as a particularly attractive candidate as amplification reaction process completes within 45 min. The first step involves multiplexing biotin and digoxigenin coated dengue and chikungunya primers respectively in LAMP reaction followed by precipitation of the amplified DNA with polyethylene glycol (PEG) buffer and finally clumping with streptavidin and anti-digoxigenin coated magnetic particle for virus discrimination and naked eye visualization. The DNA detection limit of MM LAMP visualization was 51.65 ng/µl which is comparable to the electrophoresis base UV light visualization. The results showed potential superiority over standard methods polymerase chain reaction (PCR). This current advancement empowers multiplex LAMP utility in resource limited setting without using any of the florescent dyes, turbidimeter, or the sophisticated quantitative PCR machine etc which restrict multiplex LAMP technique to laboratorial use only. We have proposed a novel method without such limitations. This technique has potential as a point of care technique for simultaneous detection of two diseases.

Development of Two-Tube Loop-Mediated Isothermal Amplification Assay for Differential Diagnosis of Plasmodium falciparum and Plasmodium vivax and Its Comparison with Loopamp™ Malaria.

To strengthen malaria surveillance, field-appropriate diagnostics requiring limited technical resources are of critical significance. Loop-mediated isothermal amplification (LAMP) based malaria diagnostic assays are potential point-of-care tests with high sensitivity and specificity and have been used in low-resource settings. Plasmodium vivax-specific consensus repeat sequence (CRS)-based and Plasmodium falciparum-specific 18S rRNA primers were designed, and a two-tube LAMP assay was developed. The diagnostic performance of a closed-tube LAMP assay and Loopamp™ Malaria Detection (Pan/Pf, Pv) kit was investigated using nested PCR confirmed mono- and co-infections of P. vivax and P. falciparum positive (n = 149) and negative (n = 67) samples. The closed-tube Pv LAMP assay showed positive amplification in 40 min (limit of detection, LOD 0.7 parasites/µL) and Pf LAMP assay in 30 min (LOD 2 parasites/µL). Pv LAMP and Pf LAMP demonstrated a sensitivity and specificity of 100% (95% CI, 95.96-100% and 89.85-100%, respectively). The LoopampTM Pan/Pf Malaria Detection kit demonstrated a sensitivity and specificity of 100%, whereas LoopampTM Pv showed a sensitivity of 98.36% (95% CI, 91.28-99.71%) and specificity of 100% (95% CI, 87.54-100%). The developed two-tube LAMP assay is highly sensitive (LOD ≤ 2 parasite/µL), demonstrating comparable results with the commercial Loopamp™ Malaria Detection (Pf/pan) kit, and was superior in detecting the P. vivax co-infection that remained undetected by the Loopamp™ Pv kit. The developed indigenous two-tube Pf/Pv malaria detection can reliably be used for mass screening in resource-limited areas endemic for both P. falciparum and P. vivax malaria.

Seroprevalence of Dengue Infection Using IgG Capture ELISA in India, 2017-2018.

We conducted a nationally representative population-based survey in 60 districts from 15 Indian states covering all five geographic regions during 2017-2018 to estimate the age specific seroprevalence of dengue. Of the 12,300 sera collected, 4,955 were positive for IgG antibodies against dengue virus using IgG Indirect ELISA indicating past dengue infection. We tested 4,948 sera (seven had inadequate volume) positive for IgG antibodies on indirect ELISA using anti-dengue IgG capture ELISA to estimate the proportion of dengue infections with high antibody titers, suggestive of acute or recent secondary infection. Of the 4,948 sera tested, 529 (10.7%; 95% CI: 9.4-12.1) were seropositive on IgG capture ELISA. The proportions of dengue infections with high titers were 1.1% in the northeastern, 1.5% in the eastern, 6.2% in the western, 12.2% in the southern, and 16.7% in the northern region. The distribution of dengue infections varied across geographic regions, with a higher proportion of infections with high antibody titer in the northern and southern regions of India. The study findings could be useful for planning facilities for clinical management of dengue infections.

Advanced Lyophilised Loop Mediated Isothermal Amplification (L-LAMP) based point of care technique for the detection of dengue virus.

Dengue virus infects millions of the people globally each year and its diagnosis remains a challenge. Conventionally used diagnostic methods are complex and time consuming. LAMP technique is a potential alternative for diagnosis of dengue virus. The benefits of LAMP are its ease and ability, as it does not require an expensive equipment and results are effortlessly visualized by the naked eye. However, it does not aid as point of care technique owing to need of contamination free area, deep freezer for chemical storage and primer self amplification. Each small modification in LAMP method bring it towards an ideal point of care technique. An advanced lyophilized loop mediated isothermal amplification (L-LAMP) was developed in which the dye was dried on the cap and reaction reagents was lyophilized at the bottom of the tube to overcome the common hurdles of LAMP technique. The technique was able to diagnose disease within 35 min with 4U of Bst polymerase. The least concentration of dye required was 1000×. Result given by the seminested reverse transcriptase polymerase chain reaction (RT-PCR) and L-LAMP with enzyme linked immuno sorbent assay (ELISA) were compared using Chi square test. The L-LAMP showed 100 % specificity and 92 % sensitivity with respect ELISA and was found better than RT-PCR which showed 100 % specificity and 88 % sensitivity. There was no cross reactivity of primers with other disease like malaria caused by Plasmodium falciparum and P. vivax and with viral disease chikungunya. L-LAMP has dynamic potential as point of care technique.

Characterization of neutralizing versus binding antibodies and memory B cells in COVID-19 recovered individuals from India.

India is one of the most affected countries by COVID-19 pandemic; but little is understood regarding immune responses to SARS-CoV-2 in this region. Herein we examined SARS-CoV-2 neutralizing antibodies, IgG, IgM, IgA and memory B cells in COVID-19 recovered individual from India. While a vast majority of COVID-19 recovered individuals showed SARS-CoV-2 RBD-specific IgG, IgA and IgM antibodies (38/42, 90.47%; 21/42, 50%; 33/42, 78.57% respectively), only half of them had appreciable neutralizing antibody titers. RBD-specific IgG, but not IgA or IgM titers, correlated with neutralizing antibody titers and RBD-specific memory B cell frequencies. These findings have timely significance for identifying potential donors for plasma therapy using RBD-specific IgG assays as surrogate measurement for neutralizing antibodies in India. Further, this study provides useful information needed for designing large-scale studies towards understanding of inter-individual variation in immune memory to SARS CoV-2 natural infection for future vaccine evaluation and implementation efforts.

Immunity against diphtheria among children aged 5-17 years in India, 2017-18: a cross-sectional, population-based serosurvey.

BACKGROUND: Diphtheria is re-emerging as a public health problem in several Indian states. Most diphtheria cases are among children older than 5 years. In this study, we aimed to estimate age-specific immunity against diphtheria in children aged 5-17 years in India. METHODS: We used residual serum samples from a cross-sectional, population-based serosurvey for dengue infection done between June 19, 2017, and April 12, 2018, to estimate the age-group-specific seroprevalence of antibodies to diphtheria in children aged 5-17 years in India. 8309 serum samples collected from 240 clusters (122 urban and 118 rural) in 60 selected districts of 15 Indian states spread across all five geographical regions (north, northeast, east, west, and south) of India were tested for the presence of IgG antibodies against diphtheria toxoid using an ELISA. We considered children with antibody concentrations of 0·1 IU/mL or greater as immune, those with levels less than 0·01 IU/mL as non-immune (and hence susceptible to diphtheria), and those with levels in the range of 0·01 to less than 0·1 IU/mL as partially immune. We calculated the weighted proportion of children who were immune, partially immune, and non-immune, with 95% CIs, for each geographical region by age group, sex, and area of residence (urban vs rural). FINDINGS: 29·7% (95% CI 26·3-33·4) of 8309 children aged 5-17 years were immune to diphtheria, 10·5% (8·6-12·8) were non-immune, and 59·8% (56·3-63·1) were partially immune. The proportion of children aged 5-17 years who were non-immune to diphtheria ranged from 6·0% (4·2-8·3) in the south to 16·8% (11·2-24·4) in the northeast. Overall, 9·9% (7·7-12·5) of children residing in rural areas and 13·1% (10·2-16·6) residing in urban areas were non-immune to diphtheria. A higher proportion of girls than boys were non-immune to diphtheria in the northern (17·7% [12·6-24·2] vs 7·1% [4·1-11·9]; p=0·0007) and northeastern regions (20·0% [12·9-29·8] vs 12·9% [8·6-19·0]; p=0·0035). INTERPRETATION: The findings of our serosurvey indicate that a substantial proportion of children aged 5-17 years were non-immune or partially immune to diphtheria. Transmission of diphtheria is likely to continue in India until the immunity gap is bridged through adequate coverage of primary and booster doses of diphtheria vaccine. FUNDING: Indian Council of Medical Research.

Advanced Multiplex Loop Mediated Isothermal Amplification (mLAMP) Combined with Lateral Flow Detection (LFD) for Rapid Detection of Two Prevalent Malaria Species in India and Melting Curve Analysis.

Isothermal techniques with lateral flow detection have emerged as a point of care (POC) technique for malaria, a major parasitic disease in tropical countries such as India. Plasmodium falciparum and Plasmodium vivax are the two most prevalent malaria species found in the country. An advanced multiplex loop-mediated isothermal amplification (mLAMP) combined with a lateral flow dipstick (LFD) technique was developed for the swift and accurate detection of P. falciparum and P. vivax, overcoming the challenges of the existing RDTs (rapid diagnostic tests). A single set of LAMP primers with a biotinylated backward inner primer (BIP primer) was used for DNA amplification of both malaria species in a single tube. The amplified DNA was hybridized with fluorescein isothiocyanate (FITC) and digoxigenin-labelled DNA probes, having a complemented sequence for the P. falciparum and P. vivax genomes, respectively. A colour band appeared on two separate LFDs for P. falciparum and P. vivax upon running the hybridized solution over them. In total, 39 clinical samples were collected from ICMR-NIMR, New Delhi. Melting curve analysis, with cross primers for both species, was used to ascertain specificity, and the sensitivity was equated with a polymerase chain reaction (PCR). The results were visualized on the LFD for both species within 60 min. We found 100% sensitivity and specificity, when compared with a traditional PCR. Melting curve analysis of mLAMP revealed the lowest detection limit of 0.15 pg/µL from sample genomic DNA. The mLAMP-LFD assays could be a potential point of care (POC) tool for early diagnosis in non-laboratory conditions, with the convenience of a reduced assay time and the simple interpretation of results.

Seroprevalence of chikungunya virus infection in India, 2017: a cross-sectional population-based serosurvey.

BACKGROUND: Since its re-emergence in 2005, chikungunya virus (CHIKV) transmission has been documented in most Indian states. Information is scarce regarding the seroprevalence of CHIKV in India. We aimed to estimate the age-specific seroprevalence, force of infection (FOI), and proportion of the population susceptible to CHIKV infection. METHODS: We did a nationally representative, cross-sectional serosurvey, in which we randomly selected individuals in three age groups (5-8, 9-17, and 18-45 years), covering 240 clusters from 60 selected districts of 15 Indian states spread across all five geographical regions of India (north, northeast, east, south, and west). Age was the only inclusion criterion. We tested serum samples for IgG antibodies against CHIKV. We estimated the weighted age-group-specific seroprevalence of CHIKV infection for each region using the design weight (ie, the inverse of the overall probability of selection of state, district, village or ward, census enumeration block, and individual), adjusting for non-response. We constructed catalytic models to estimate the FOI and the proportion of the population susceptible to CHIKV in each region. FINDINGS: From June 19, 2017, to April 12, 2018, we enumerated 117 675 individuals, of whom 77 640 were in the age group of 5-45 years. Of 17 930 randomly selected individuals, 12 300 individuals participated and their samples were used for estimation of CHIKV seroprevalence. The overall prevalence of IgG antibodies against CHIKV in the study population was 18·1% (95% CI 14·2-22·6). The overall seroprevalence was 9·2% (5·4-15·1) among individuals aged 5-8 years, 14·0% (8·8-21·4) among individuals aged 9-17 years, and 21·6% (15·9-28·5) among individuals aged 18-45 years. The seroprevalence was lowest in the northeast region (0·3% [95% CI 0·1-0·8]) and highest in the southern region (43·1% [34·3-52·3]). There was a significant difference in seroprevalence between rural (11·5% [8·8-15·0]) and urban (40·2% [31·7-49·3]) areas (p<0·0001). The seroprevalence did not differ by sex (male 18·8% [95% CI 15·2-23·0] vs female 17·6% [13·2-23·1]; p=0·50). Heterogeneous FOI models suggested that the FOI was higher during 2003-07 in the southern and western region and 2013-17 in the northern region. FOI was lowest in the eastern and northeastern regions. The estimated proportion of the population susceptible to CHIKV in 2017 was lowest in the southern region (56·3%) and highest in the northeastern region (98·0%). INTERPRETATION: CHIKV transmission was higher in the southern, western, and northern regions of India than in the eastern and northeastern regions. However, a higher proportion of the population susceptible to CHIKV in the eastern and northeastern regions suggests a susceptibility of these regions to outbreaks in the future. Our survey findings will be useful in identifying appropriate target age groups and sites for setting up surveillance and for future CHIKV vaccine trials. FUNDING: Indian Council of Medical Research.

Genetic changes of Plasmodium vivax tempers host tissue-specific responses in Anopheles stephensi.

Recently, we showed how an early restriction of gut flora proliferation by Plasmodium vivax favors immune-suppression and Plasmodium survival in the gut lumen (Sharma et al., 2020). Here, we asked post gut invasion how P. vivax interacts with individual tissues such as the midgut, hemocyte, and salivary glands, and manages its survival in the mosquito host. Our data from tissue-specific comparative RNA-Seq analysis and extensive temporal/spatial expression profiling of selected mosquito transcripts in the uninfected and P. vivax infected mosquito's tissues indicated that (i) a transient suppression of gut metabolic machinery by early oocysts; (ii) enriched expression of nutritional responsive proteins and immune proteins against late oocysts, together may ensure optimal parasite development and gut homeostasis restoration; (iii) pre-immune activation of hemocyte by early gut-oocysts infection via REL induction (p â€‹< â€‹0.003); and altered expression of hemocyte-encoded immune proteins may cause rapid removal of free circulating sporozoites from hemolymph; (iv) while a strong suppression of salivary metabolic activities, and elevated expression of salivary specific secretory, as well as immune proteins together, may favor the long-term storage and survival of invaded sporozoites. Finally, our RNA-Seq-based discovery of 4449 transcripts of Plasmodium vivax origin, and their developmental stage-specific expression modulation in the corresponding infected mosquito tissues, predicts a possible mechanism of mosquito responses evasion by P. vivax. Conclusively, our system-wide RNA-Seq analysis provides the first genetic evidence of direct mosquito-Plasmodium interaction and establishes a functional correlation.

Hepatitis-B virus infection in India: Findings from a nationally representative serosurvey, 2017-18.

INTRODUCTION: India introduced a hepatitis-B (HB) vaccine in the Universal Immunization Program in 2002-2003 on a pilot basis, expanded to ten states in 2007-2008 (phase-1), and the entire country in 2011-2012 (phase-2). We tested sera from a nationally representative serosurvey conducted duing 2017, to estimate the seroprevalence of different markers of HB infection among children aged 5-17 years in India and to assess the impact of vaccination. METHODS: We tested sera from 8273 children for different markers of HB infection and estimated weighted age-group specific seroprevalence of children who were chronically infected (HBsAg and anti-HBc positive), and immune due to past infection (anti-HBc positive and HBsAg negative), and having serological evidence of HB vaccination (only anti-HBs positive). We compared the prevalence of serological markers among children born before (aged 11-17 years) and after (aged 5-10 years) introduction of HB-vaccine from phase-1 states. RESULTS: Among children aged 5-8 years, 1.1% were chronic carriers, 5.3% immune due to past infection, and 23.2% vaccinated. The corresponding proportions among children aged 9-17 years were 1.1%, 8.0%, and 12.0%, respectively. In phase-1 states, children aged 5-10 years had a significantly lower prevalence of anti-HBc (4.9% vs. 7.6%, p<0.001) and higher prevalence of anti-HBs (37.7% vs. 14.7%, p<0.001) compared to children aged 11-17 years. HBsAg positivity, however, was not different in the two age groups. CONCLUSIONS: Children born after the introduction of HB vaccination had a lower prevalence of past HBV infection and a higher prevalence of anti-HBs. The findings of our study could be considered as an interim assessment of the impact of the hepatitis B vaccine introduction in India.

Detection of Dengue Virus-Specific IgM and IgG Antibodies through Peptide Sequences of Envelope and NS1 Proteins for Serological Identification.

Dengue is an acute febrile illness caused by positive-sense single-stranded RNA virus, belonging to the family Flaviviridae and genus Flavivirus. Transmission of virus among the individuals occurred by blood-feeding Aedes mosquitoes. This virus has four serotypes differentiated on the basis of antibody neutralization assay. At present, there is no particular treatment or vaccine candidate available for dengue infection. Approximately 3.9 billion human populations are at risk of dengue virus (DENV) infection. Thus, precise diagnosis of dengue at the early stage is very essential for disease control and effective therapy in order to treat or prevent severe complications. Indeed, the accurate diagnosis of DENV remains a problem because of low detection accuracy along with high testing price. Sensitivity and specificity of available kits vary from test to test, and cross-reactivity with other Flavivirus is a challenging issue for diagnosis. In this study, linear epitopes of envelope (E) and NS1 proteins were identified to diagnose the DENV. Whole protein sequences of E and NS1 of DENV were obtained from UniProtKB database. On the basis of algorithm prediction from DNASTAR, BCEPRED, and IEDB data resources, twelve peptides of E (EP1 to EP12) and eight peptides of NS1 (NS1-1 to NS1-8) were selected, which were common in all serotypes. Sequence homologies of peptides with other Flavivirus were checked by Multiple Sequence Alignment Tool ClustalX2. Peptide sequences were synthesized chemically by solid-phase peptide synthesis technique. Dengue-specific IgM and IgG (secondary response) antibodies in the patient's antisera were tested with the peptides using ELISA protocol. Peptides EP1, EP2, EP4, EP7, EP10, and EP12 of E protein and NS1-1, NS1-3, NS1-4, NS1-7, and NS1-8 of NS1 protein were considered the best immunoreactive peptides with the sensitivity (73.33-96.66%) and specificity (82.14-100%). Such peptides together can be used to construct the multiple antigen peptides (MAP) or multiplexed microbeads for designing a precise, cost-effective, and easy-to-make peptide-based immunodiagnostic kit for DENV detection.

Altered Gut Microbiota and Immunity Defines Plasmodium vivax Survival in Anopheles stephensi.

Blood-feeding enriched gut-microbiota boosts mosquitoes' anti-Plasmodium immunity. Here, we ask how Plasmodium vivax alters gut-microbiota, anti-Plasmodial immunity, and impacts tripartite Plasmodium-mosquito-microbiota interactions in the gut lumen. We used a metagenomics and RNAseq strategy to address these questions. In naïve mosquitoes, Elizabethkingia meningitis and Pseudomonas spp. are the dominant bacteria and blood-feeding leads to a heightened detection of Elizabethkingia, Pseudomonas and Serratia 16S rRNA. A parallel RNAseq analysis of blood-fed midguts also shows the presence of Elizabethkingia-related transcripts. After, P. vivax infected blood-meal, however, we do not detect bacterial 16S rRNA until circa 36 h. Intriguingly, the transcriptional expression of a selected array of antimicrobial arsenal cecropins 1-2, defensin-1, and gambicin remained low during the first 36 h-a time frame when ookinetes/early oocysts invaded the gut. We conclude during the preinvasive phase, P. vivax outcompetes midgut-microbiota. This microbial suppression likely negates the impact of mosquito immunity which in turn may enhance the survival of P. vivax. Detection of sequences matching to mosquito-associated Wolbachia opens a new inquiry for its exploration as an agent for "paratransgenesis-based" mosquito control.

Delayed haemolysis after treatment with intravenous artesunate in patients with severe malaria in India.

BACKGROUND: Parenteral artesunate is the treatment of choice for severe malaria. It is safe, efficacious and well tolerated anti-malarial. However, delayed haemolysis has been reported in travellers, non-immune individuals and in African children. METHODS: A prospective, observational study was carried out in admitted severe malaria patients receiving parenteral artesunate. The patients were followed up until day 28 for monitoring clinical as well as laboratory parameters for haemolytic anaemia. RESULTS: Twenty-four patients with severe malaria receiving injection artesunate were enrolled in the study. Post-artesunate delayed haemolysis following parenteral artesunate therapy was observed in three of 24 patients (12.5%, 95% confidence interval 4.5-31.2%). Haemolysis was observed in two more patients possibly due to other reasons. The haemoglobin fall ranged from 13.6 to 38.3% from day 7 to day 28 in these patients. CONCLUSION: The possibility of delayed haemolysis should be considered while treating the severe malaria patients with parenteral artesunate. The study highlights the need for further studies in different epidemiological settings.

Socioeconomic determinants of community knowledge and practice in relation to malaria in high- and low-transmission areas of central India.

This study was undertaken with an aim of exploring community knowledge and treatment practices related to malaria and their determinants in high- and low-transmission areas of central India. A community-based cross-sectional study was carried out between August 2015 and January 2016 in two high- and two low-malaria-endemic districts of central India. A total of 1470 respondents were interviewed using a pre-tested structured interview schedule. Respondents residing in high-transmission areas with higher literacy levels, and of higher socioeconomic status, were found to practise more modern preventive measures than those living in low-transmission areas with low literacy levels and who were economically poor. Level of literacy, socioeconomic status and area (district) of residence were found to be the main factors affecting people's knowledge of malaria aetiology and clinical features, and prevention and treatment practices, in this community in central India.

Geographical distribution of primary & secondary dengue cases in India - 2017: A cross-sectional multicentric study.

Background & objectives: Dengue virus infection is endemic in India with all the four serotypes of dengue virus in circulation. This study was aimed to determine the geographic distribution of the primary and secondary dengue cases in India. Methods: A multicentre cross-sectional study was conducted at Department of Health Research / Indian Council of Medical Research (DHR)/(ICMR) viral research and diagnostic laboratories (VRDLs) and selected ICMR institutes located in India. Only laboratory-confirmed dengue cases with date of onset of illness less than or equal to seven days were included between September and October 2017. Dengue NS1 antigen ELISA and anti-dengue IgM capture ELISA were used to diagnose dengue cases while anti-dengue IgG capture ELISA was used for identifying the secondary dengue cases. Results: Of the 1372 dengue cases, 897 (65%) were classified as primary dengue and 475 (35%) as secondary dengue cases. However, the proportion varied widely geographically, with Theni, Tamil Nadu; Tirupati, Andhra Pradesh and Udupi-Manipal, Karnataka reporting more than 65 per cent secondary dengue cases while Srinagar, Jammu and Kashmir reporting as low as 10 per cent of the same. The median age of primary dengue cases was 25 yr [interquartile range (IQR 17-35] while that of secondary dengue cases was 23 yr (IQR 13.5-34). Secondary dengue was around 50 per cent among the children belonging to the age group 6-10 yr while it ranged between 20-43 per cent among other age groups. Interpretation & conclusions: Our findings showed a wide geographical variation in the distribution of primary and secondary dengue cases in India. It would prove beneficial to include primary and secondary dengue differentiation protocol in the national dengue surveillance programme.

Burden of dengue infection in India, 2017: a cross-sectional population based serosurvey.

BACKGROUND: The burden of dengue virus (DENV) infection across geographical regions of India is poorly quantified. We estimated the age-specific seroprevalence, force of infection, and number of infections in India. METHODS: We did a community-based survey in 240 clusters (118 rural, 122 urban), selected from 60 districts of 15 Indian states from five geographical regions. We enumerated each cluster, randomly selected (with an Andriod application developed specifically for the survey) 25 individuals from age groups of 5-8 years, 9-17 years, and 18-45 years, and sampled a minimum of 11 individuals from each age group (all the 25 randomly selected individuals in each age group were visited in their houses and individuals who consented for the survey were included in the study). Age was the only inclusion criterion; for the purpose of enumeration, individuals residing in the household for more than 6 months were included. Sera were tested centrally by a laboratory team of scientific and technical staff for IgG antibodies against the DENV with the use of indirect ELISA. We calculated age group specific seroprevalence and constructed catalytic models to estimate force of infection. FINDINGS: From June 19, 2017, to April 12, 2018, we randomly selected 17 930 individuals from three age groups. Of these, blood samples were collected and tested for 12 300 individuals (5-8 years, n=4059; 9-17 years, n=4265; 18-45 years, n=3976). The overall seroprevalence of DENV infection in India was 48·7% (95% CI 43·5-54·0), increasing from 28·3% (21·5-36·2) among children aged 5-8 years to 41·0% (32·4-50·1) among children aged 9-17 years and 56·2% (49·0-63·1) among individuals aged between 18-45 years. The seroprevalence was high in the southern (76·9% [69·1-83·2]), western (62·3% [55·3-68·8]), and northern (60·3% [49·3-70·5]) regions. The estimated number of primary DENV infections with the constant force of infection model was 12 991 357 (12 825 128-13 130 258) and for the age-dependent force of infection model was 8 655 425 (7 243 630-9 545 052) among individuals aged 5-45 years from 30 Indian states in 2017. INTERPRETATION: The burden of dengue infection in India was heterogeneous, with evidence of high transmission in northern, western, and southern regions. The survey findings will be useful in making informed decisions about introduction of upcoming dengue vaccines in India. FUNDING: Indian Council of Medical Research.

An epidemiological study of dengue and its coinfections in Delhi.

OBJECTIVES: To study the epidemiology of dengue with reference to serological, demographic profile, spatio-temporal distribution, vectors, circulating serotypes and coinfections. METHODS: Demographic data and presenting symptoms of fever cases reporting to the clinic were recorded. Suspected patients were tested for dengue, chikungunya and malaria. Dengue specific RT-PCR was performed to detect circulating DENV serotypes. Vector surveys were carried out to detect Aedes breeding. RESULTS: Of the 5536 fever patients tested during 2012 to 2015, 1536 (27.7%) had confirmed dengue. The peak in dengue positivity was observed during September and October. Of the 60 samples analysed, 10 (16.7%) had concurrent infection with multiple dengue serotypes; one of them had all the four serotypes. Coinfection of dengue with malaria and chikungunya was also observed. The occurrence of dengue and malaria was inversely related. Seven percent of the dengue patients required hospitalization. Vector surveys in the draining area revealed Aedes breeding with a high house index. CONCLUSION: Delhi being hyperendemic, the occurrence of concurrent infections with multiple DENV serotypes has become a frequent finding. The study emphasizes the need of epidemiological and entomological surveillance to monitor trends in dengue distribution, seasonal patterns and circulating serotypes to guide dengue control activities.