|SHORT RESEARCH COMMUNICATION
|Year : 2019 | Volume
| Issue : 4 | Page : 380-382
Dengue fever outbreak by more than one serotype in a municipal area of Kolkata, Eastern India
Falguni Debnath1, Ch Sadhukhan Provash2, Avijit Chakraborty1, Shanta Dutta3
1 Division of Epidemiology, ICMR–National Institute of Cholera & Enteric Diseases, Kolkata, India
2 Virus unit, ICMR–National Institute of Cholera & Enteric Diseases, Kolkata, India
3 Division of Bacteriology, ICMR–National Institute of Cholera & Enteric Diseases, Kolkata, India
|Date of Submission||30-Jan-2019|
|Date of Acceptance||02-Aug-2019|
|Date of Web Publication||30-Nov-2020|
Scientist C, Division of Epidemiology, ICMR–National Institute of Cholera and Enteric Diseases, P- 33, CIT Rd, Scheme XM, Beliaghata, Kolkata 700010
Source of Support: None, Conflict of Interest: None
A dengue outbreak struck Baranagar municipality area of North 24 Parganas district, West Bengal in July 2016. This study presents the epidemiological and virology findings of this outbreak. The outbreak started from 17 July and continued until 17th December. Total 1660 dengue cases (overall attack rate: 7/1000) and two deaths (case fatality rate: 1/1000) were reported. All age groups were affected. Out of the 213 blood samples collected from probable dengue cases and tested at Virus Unit, ICMR-National Institute of Cholera & Enteric Diseases (NICED), Kolkata, 163 (76%) tested seropositive through NS1 / IgM ELISA confirming dengue infection. DENV 1 was the predominant (53%, 44/83) serotype followed by DENV 2 (23%, 19/83), DENV 4 (15.6%, 13/83), DENV 3 (8.4%,7/ 83). Coexistence of dengue and chikungunya virus infection was detected. Major presentation of the confirmed dengue cases was fever with headache (95%), followed by arthralgia, myalgia, retro-orbital pain, abdominal pain, diarrhoea, and rash. Abundance of vector breeding spaces was observed in the area. Accordingly the health authorities were suggested to conduct frequent mass awareness campaigns involving community to reduce breeding sources during pre-monsoon and monsoon months. Further, adult mosquito control measures were also suggested throughout the year and inter-departmental coordination was recommended for prevention of such outbreaks in future.
Keywords: Chikungunya co-infection; DENV 1; DENV 2; dengue fever; IgM ELISA; NS1 ELSA
|How to cite this article:|
Debnath F, Provash CS, Chakraborty A, Dutta S. Dengue fever outbreak by more than one serotype in a municipal area of Kolkata, Eastern India. J Vector Borne Dis 2019;56:380-2
|How to cite this URL:|
Debnath F, Provash CS, Chakraborty A, Dutta S. Dengue fever outbreak by more than one serotype in a municipal area of Kolkata, Eastern India. J Vector Borne Dis [serial online] 2019 [cited 2021 Jan 25];56:380-2. Available from: https://www.jvbd.org/text.asp?2019/56/4/380/302043
India has emerged as a major contributor to the global dengue burden and the epidemiology of dengue is thought to be much complex here. The first virologically confirmed dengue fever epidemic was reported from Calcutta, presently known as Kolkata in 1963-64. After that in 1966, epidemics were reported from northern Indian states and not much later dengue fever epidemics struck southern Indian states also. All the four serotypes are circulating in India. But, replacement of DENV 2 and 3 by DENV 1 as predominant serotype was reported from epidemics in Delhi. At the same time, co-infection with dengue and chikungunya virus (CHIKV) exists in India as the dengue epidemic areas overlap with chikungunya prone areas.
In September 2016, clustering of fever cases was observed in Baranagar Municipal area of North 24 Parganas District, West Bengal, India and the same was investigated during September-December 2016 with the objectives: (1) to confirm the occurrence of dengue outbreak; (2) to describe it in terms of time, place, person; (3) to establish the etiological agent and (4) to recommend the control measures.
Prior to the current investigation on fever (suspected dengue) cases, data on confirmed dengue cases during 2013-2015 and for January-August 2016 were collected from North 24 Parganas district health authority to calculate and compare the monthly incidences (per lakh population) of dengue. Three methodologies were adopted during the study period for identifying probable and confirmed dengue cases: (i) Door to door active case search in a specific Ward (No. 1) of Baranagar municipality using a dengue case search tool; (ii) Clinical identification of probable dengue cases from indoor/ outdoor departments of Baranagar State General Hospital (BSGH), Kolkata; (iii) Review of medical records of dengue cases available with district health authority.
The National Vector Borne Disease Control Programme (NVBDCP) case definitions were followed to identify probable and confirmed dengue cases. Blood specimens of probable dengue cases collected during active case search activity were tested by MAC IgM ELISA (PanBio, Australia) and NS1 ELISA (PanBio, Australia) for confirmation at ICMR-National Institute of Cholera & Enteric Diseases, Virus Unit laboratory, Kolkata. Dengue RNA detection and serotyping were done by nested RT-PCR according to the method of Lanciotti et al. Chikungunya infection was also screened using MAC-IgM ELISA test (Standard Diagnostics, Germany). Trained municipal health workers conducted entomological and environmental survey in that area opting purposive sampling method. The Aedes larvae were identified by visual inspection of their appearance and movement in water,.
During January to August of 2013-2015, not much cases of dengue were observed. But, in 2016, there was an upsurge of dengue cases since the month of July showing an incidence of 13/100,000 and in August it went up to 230/100,000, justifying the evidence of occurrence of an outbreak. During the entire outbreak period, i.e. 17th July to 17th December 2016 [Figure 1], 1660 residents ofBaranagar area were detected as dengue positives, of which 85% of the blood specimens (1413/1660) were positive for NS1 ELISA, and rest were positive for IgM ELISA.
|Figure 1: Distribution of confirmed dengue cases by week of onset, Baranagar Municipality, North 24 Parganas, West Bengal, India, July – December 2016 (with control measures adopted).|
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Review of records revealed that all 34 administrative Wards of Baranagar municipality were affected. Highest attack rate (11/1000) was reported from Ward 11. All age groups were affected (mean age: 29.7 yr, SD: 14.1 yr) and two dengue deaths occurred [Table 1].
|Table 1: Age and gender specific attack rate of dengue fever cases, Baranagar, North 24 Parganas, West Bengal, India, July–December 2016|
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During the investigation, blood specimens from 213 probable dengue cases were collected and tested serologically for confirmation; 163 (76%, 163/213) were seropositive for dengue either by NS1 or IgM ELISA. A total of 83 positive specimens were serotyped and DENV 1 was found as the most common serotype (53%, 44/83) followed by DENV 2 (23%,19/83), DENV4 (15.6%, 13/ 83) and DENV 3 (8.4%,7/83). When Chikungunya test was performed on 117 specimens, 14 (12%) were positive, of which nine specimens showed presence of both infections. Among 163 confirmed dengue cases, most common symptoms were headache (95%), arthralgia (87%), followed by myalgia, retro-orbital pain, abdominal pain, diarrhea, and only 9% developed rash.
Further, 100 households in the study ward were searched for water holding containers. The house index was 5%, container index was 3% and Breteau index was 6 per 100 households. It was observed that most of the households stored water in uncovered tanks, vessels; water accumulation was noted in discarded cold drink bottles, plastic cups, broken flower vases, flower pots etc.
A shift in the predominant circulating serotype of dengue virus was reported from northern part of India during 2010 to 2013. In 2010, DENV 1 was the predominant serotype in Delhi, whereas, in 2013, DENV 2 emerged as predominant serotype,. Studies from eastern part of India, also showed a shift in the prevalent serotype over the years. From 2008 till 2010, DENV 1, 2, 4 were the major circulating serotypes, but in 2012, DENV 3 emerged as the major serotype and led to a massive outbreak in Kolkata. In this study, again DENV 1 was found as the major circulating serotype causing outbreak. During 1963-65, the first chikungunya and dengue virus coinfection was reported from Kolkata. Chikungunya virus re-emerged in this region during 2006. This study also, reports few cases where both the infections were present, which can be explained in terms of common vectors for transmission of both the viruses.
Environmental factors are critical for development of vector borne diseases. There are reports of dengue epidemics during the warm, humid, rainy seasons, as they favour mosquito growth,. In this study, clustering of dengue cases started appearing during monsoon season, corroborating the findings of previous studies. Apparently, abundance of vector breeding spaces might have facilitated occurrence of the current outbreak.
Low Aedes aegypti larval indices found in entomological survey conducted in November 2016, indicated towards cessation of vector transmission, which was in coherence with the epidemiological findings. The study had limitations as active case search, entomological and environmental survey were restricted to one ward of Baranagar. Entomological survey did not include laboratory examination for species identification of larvae.
Based on the study findings, the Municipal health authorities were suggested to conduct frequent mass awareness campaigns involving community to reduce breeding sources during pre-monsoon and monsoon months. Adult mosquito control measures were also suggested throughout the year and inter departmental coordination was recommended for prevention of such outbreaks in future.
Outbreak investigation is a routine activity of ICMR- National Institute of Cholera & Enteric Diseases (NICED), Kolkata. Since the study was conducted during the outbreak/emergency, separate ethical permission to investigate the dengue outbreak at Baranagar Municipal area was not needed.
Conflict of interest: No potentail conflict of interest exists among the authors.
| Acknowledgements|| |
The authors acknowledge the district health officials of North 24 Parganas district, Baranagar Municipal Health officials, and health workers for their kind support and help.
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