Transfusion-transmitted infections (TTIs) impose meticulous screening protocols in blood banks. Emerging or re-emerging viruses with altered pathogenicity remains debatable whether or not to include those in TTI screening panel. Dengue infection is known to transmit via Aedes aegypti mosquito; however, the route of infection through blood transfusion is recently of greater importance. India with hyper-endemic and endemic dengue regions must guarantee the safety in transfusion-related products. The donor with asymptomatic dengue infection during viremic phase can act as a reservoir for transmission. The acute infection in dengue is ascertained by detecting either nonstructural-1 protein (NS1) or IgM antibody whereas the prevalence of dengue can be monitored by the presence of IgG. The presence of viremia in blood related products need to be assessed. However, reports on transfusion transmissible dengue infection are still lacking in this part of India. Therefore, the present study aims to determine the dengue NS1 protein and IgM status among blood donors collected at a tertiary care hospital in Southern India. Fortunately, we receive samples for routine dengue testing from patients residing in and around camp area. Hence, the latter part of this study is designed to substantiate the active circulation of dengue virus in and around camp area during camp period. A single blinded randomized pilot study was designed for which serum samples those were negative to TTIs were collected from Department of Transfusion Medicine. The remaining serum of non-reactive samples collected during blood donation camp organized at Surulipatti village (9.7059°N, 77.3016°E) of Theni district on 30th September 2017 was taken for this study. The samples were de-identified and assigned a donor number from one to 95. Once collected, the samples were aliquoted into small vials and kept in deep freezers at −20 ℃. NS1 protein and dengue specific IgM detection was carried out by Panbio™ Dengue Early ELISA (Abbott Diagnostics, Korea) and IgM capture ELISA (National Institute of Virology, India) respectively. Samples positive to either one of the above tests were subjected to Panbio™ IgG ELISA (Abbott Diagnostics, Korea). All the tests were performed and the interpretation of results was done as per the manufacturer’s instructions provided in the kit. Appropriate controls from the kits and the in-house controls prepared from positive samples were added in each run. The active circulation of the dengue virus in and around the study area was evidenced by two factors: duration and location. Villages near the blood camp were identified by point-radius method using Maptive software (www.maptive.com)[1]. The duration for data stratification was calculated on the basis of maximum incubation period of dengue virus (i.e) 10 days. The data pertaining to hospitalized dengue cases were downloaded in the form of Microsoft Excel sheet from NIE server (http://112.133.207.124:82/vdln/) maintained by National Institute of Epidemiology, Chennai, Tamilnadu. The sorting was done based on the closest villages identified earlier and the date on which the sample was tested. Furthermore, the resultant samples those were tested only for IgM was retrospectively tested for NS1 antigen using stored serum. Once dengue testing was completed, the positive and negative status of individual donor for each assay was represented as D (donor number) followed by NS1+/-/IgM+/e/-/IgG+/-. The positivity was expressed in percentage and their combinations were depicted in proportional Venn diagram using Biovenn online software with some modifications[2]. The dengue cases filtered from hospital-based data were tabulated with their respective positives. We tested 95 blood donor samples for dengue infection. Of these, 8 (8.4%) samples were positive to NS1 (2, 2.1%) and/or IgM (6, 6.3%) as per kit cut off values (Table 1). Our study revealed that all NS1 positive samples (D25/NS1+/IgM-/IgG- and D50/NS1+/IgMe/IgG-) were IgG negative. Out of six IgM positives, two donor samples (D46 and D81) turned out to be IgG negative (Figure 1). A total of 293 records were downloaded between 20th September and 10th October 2017. Point radius method found that four villages were close to the camp area. Using this, filter applied to ‘village column’ sorted 16 dengue suspected cases, of which, seven (43.7%) had dengue infection. Two positive NS1 cases were identified and one belonged to the village of Surulipatti.
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