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 Table of Contents  
ORIGINAL ARTICLE
Year : 2019  |  Volume : 6  |  Issue : 1  |  Page : 32-36

Outbreak investigation and containment measures of dengue fever in rural Wardha: A field epidemiological study


Department of Community Medicine, Mahatma Gandhi Institute of Medical Sciences, Wardha, Maharashtra, India

Date of Submission10-Oct-2018
Date of Acceptance30-Mar-2019
Date of Web Publication10-Jul-2019

Correspondence Address:
Dr. Sourav Goswami
Department of Community Medicine, Mahatma Gandhi Institute of Medical Sciences, Sevagram, Wardha- 442 102, Maharashtra
India
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Source of Support: None, Conflict of Interest: None


DOI: 10.4103/IJAMR.IJAMR_69_18

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  Abstract 


Background: Dengue is a common vector-borne disease in countries like India, where it occurs in specific pockets including many in Maharashtra. During July–August 2018, an outbreak of dengue was suspected in a village of Wardha district, following an increase in the number of fever cases from the village, which demanded an urgent outbreak investigation to be carried out before it progressed into an epidemic/larger outbreak. Objectives: The aim of this study was to find out more cases, source of infection and to recommend necessary actions to control the dengue outbreak. Materials and Methods: This was a cross-sectional epidemiological study, where we used pre-tested, pre-designed epidemiological case sheets obtained from Integrated Disease Surveillance Program (IDSP). A case definition was proposed before beginning the investigation. Line listing, collection of blood samples, distribution of paracetamol tablets to fever cases, and making a spot map were some of the important steps carried out during the investigation. Results: Out of a total of 64 suspected fever cases, 36 cases fulfilled the case definition of dengue, set for the purpose of outbreak investigation. Twenty-three of them got admitted in different hospitals among whom two of them died. Apart from that, four of them were found to be positive for both dengue IgM and NS1 antigen in their blood samples. It was age group of 21–30 years which was mostly affected. Compared to males, the female population suffered more from the illness. House, container, and Breteau index were found to be 0.26, 0.09, and 0.32, respectively. Conclusion: Following the investigation, a detailed report was made, which was shared with the district health authority. The report also contained recommendations for necessary actions to be taken to control this outbreak and to further prevent such outbreaks in future.

Keywords: Dengue, field epidemiology, India, outbreak investigation


How to cite this article:
Goswami S, Jha A, Siven SP, Mundra A, Gupta SS, Dambhare D, Raut A, Mehendale A. Outbreak investigation and containment measures of dengue fever in rural Wardha: A field epidemiological study. Int J Adv Med Health Res 2019;6:32-6

How to cite this URL:
Goswami S, Jha A, Siven SP, Mundra A, Gupta SS, Dambhare D, Raut A, Mehendale A. Outbreak investigation and containment measures of dengue fever in rural Wardha: A field epidemiological study. Int J Adv Med Health Res [serial online] 2019 [cited 2019 Sep 16];6:32-6. Available from: http://www.ijamhrjournal.org/text.asp?2019/6/1/32/262495




  Introduction Top


Dengue is one of the most rapidly spreading mosquito-borne viral diseases among humans and is endemic in many countries in the tropical and subtropical regions of the world.[1] In the first report of the World Health Organization (WHO) on Neglected Tropical Diseases (NTDs), dengue was listed as one of the NTDs by the WHO.[2]

In India, the occurrence of dengue fever (DF) is known since 1956 and the first outbreak occurred in 1963 in Kolkata. At present, dengue cases are reported from all parts of the country except Lakshwadeep.[3] Since the first outbreak, dengue outbreaks still continue to occur each year in different parts of the country. The number of outbreaks has also been on the rise with time. In 2009 [Figure 1], about 20 outbreaks of dengue were reported throughout India, which rose to 177 in 2016. In the last decade, close to a thousand outbreaks have been reported.[4],[5],[6],[7]
Figure 1: Dengue outbreaks in India. Data source: National Centre for Disease Control Annual Report 2016-17[4]

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The number of dengue cases surges during the rainy season, when the mosquito gets ample amount of stagnant water for breeding, thus helping the spread of the disease. Previously, it was believed that dengue is limited to urban areas due to its vector characteristics, but recently, the vector has undergone a change in the characteristics; hence, a change in the epidemiology and now, the number of dengue cases from the rural areas is on the rise.[8]

During July–August 2018, an outbreak of dengue was suspected in a village of Wardha District, following an increase in the number of fever cases from the village. Since a few cases were diagnosed to have dengue, we undertook an epidemiological and vector survey to find the source(s) of the infection and suggest measures to contain the outbreak before it progressed into an epidemic/larger outbreak leading to higher mortality and morbidity.


  Materials and Methods Top


Study setting

The study area, Kelapur is a village that has a population of about 992 people with 248 households. It falls in Wardha Taluka of Wardha District. The geographical coordinates of the village are 20° 7216620' N, and 78° 4361470' E. The village falls under Waifad Primary Health Centre and Dahegaon (station) Sub Centre. The village is situated around 30 km from Wardha.

The village is located in a plain land. Well water is the main source of drinking water, apart from pipe water. A small runnel (nala) runs through the village. Most of the waste water generated from the houses are drained into it. Due to the sluggish flow of water in the runnel, a number of small pools of stagnant water are present in the runnel. The villagers store water in drums and overhead tanks, most of which are uncovered.

Although latrines are there in most of the houses, open field defecation is still practiced in the area. Solid waste, including cow dung is dumped in the fields beside their place of residence.

Intermittent rainfall occurs during late July–October each year. Sporadic cases of dengue, malaria were common, but till the recent incident, no cases of outbreak of DF had occurred previously.

Case definitions

The case definition used was in accordance with the WHO recommended surveillance standards which is also used in IDSP.[9] The case definition was as follows:

Any acute-onset fever of 2–7 days duration with, two or more of the following: (i) headache; (ii) retro-orbital pain; (iii) myalgia; (iv) arthralgia; (v) rash; and (vi) hemorrhagic manifestations with two or more of the following: (a) Testing positive for NS1 antigen; (b) positive IgM antibody test for dengue; (c) epidemiologically linked with a confirmed case of DF; and (d) leukopenia.

Data collection

A team of 20 people including six faculty members, six postgraduate students, four interns, two social workers, one auxiliary nurse midwife, and one laboratory technician from Mahatma Gandhi Institute of Medical Sciences (MGIMS), Sevagram visited Kelapur, Wardha to investigate an epidemic of dengue reported from there on August 6, 2018.

The activities carried out by the team to investigate were as follows:

  1. Line listing of the cases
  2. Investigation of probable cases to find out the cause of the epidemic
  3. Observation of the water containers and the presence of mosquito breeding sites in the households
  4. Observation of breeding places of mosquitoes in and around the village
  5. Vector survey
  6. Distribution of paracetamol tablets
  7. Preparation of spot map.


Line listing

The team members were divided into seven groups that contained a volunteer from the village who knew the village well. Each group had a village map and the area of their movement was marked previously to cover each and every household.

Investigation of suspected cases

Blood samples were collected from the villagers who were suspected to be suffering from dengue and still had the fever. The samples were transported to the Microbiology Department, MGIMS, Sevagram in cold chain for investigation. A separate case investigation form was filled up for each of the suspected case.

Observation of the water containers in households

During the line listing exercise, while one of the group members was taking the history, the other one inspected the house, and counted the numbers of water storing containers in that house and also noted the number of containers where mosquito was breeding.

Observation of breeding places of mosquitoes in and around the village

All the wells, drains and the runnel (nala) in the village were observed for potential mosquito breeding.

Vector surveys

Immature surveys were also carried out in all the colonies to estimate the Aedes larval breeding indices such as house index (HI), container index (CI), and Breteau index (BI).[6] Larval samples collected from water receptacles were reared to adults for identification.

Distribution of paracetamol tablets

Paracetamol tablets (six tablets for each patient) were distributed to all the fever cases that were found out during the line listing.

Spot map

Spot maps were made using GPS (Google Map) by one member of each group while visiting the families.

Statistical analysis

Data were entered and analyzed in Microsoft Excel.

Management of cases

All the villagers who were found to be suffering from dengue was referred by ambulance to MGIMS and immediate symptomatic treatment was started. Three cases with very low platelet count were transfused with platelet concentrate.

The field epidemiological investigation was conducted with the support from District Health Officer, Wardha and the findings of the investigation are now being disseminated maintaining the anonymity and confidentiality of the individual participants.


  Results Top


On July 18, 2018, two patients from Kelapur of Wardha district got admitted in the district hospital with the chief complaints of fever, malaise, body ache, and retro-orbital pain. Following this, there was more admission of patients with similar complaints in the district hospital as well as in the medical college that continued for the next 2 weeks. The admitted patients were triaged, and many of them had to be taken into the intensive care unit. Symptomatic treatment was started, and blood samples were sent for different microbiological and pathological investigations, following which cases of dengue were diagnosed. Soon after the diagnosis was confirmed, a team comprising of public health specialists, postgraduate students, interns, social workers, and a laboratory technician was constituted. The epidemiological team visited the village to find out more number of cases and the cause of the epidemic. Soon after the investigation was done, a detailed report was made and sent to the District Health Authority with recommendations to take further action.

Descriptive epidemiology

Distribution of fever cases

The team identified a total of 64 fever cases, of which 36 were the suspected cases of dengue as per the case definition of dengue, set for the purpose of outbreak investigation. Twenty-three of them got admitted in different hospitals - MGIMS, Sevagram and Wardha District hospital. There were two deaths reported as a result of dengue. Apart from this, there were four laboratory-confirmed cases. The date of onset of the symptoms (mostly fever) was noted for the fever cases from the beginning till the end of the outbreak, and an epidemic curve was constructed based on this observation [Figure 2].
Figure 2: Epidemic curve for dengue in the village of investigation

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The age distribution of the fever cases is presented in [Table 1]. The age group of 21–30 years was mostly affected, followed by 11–20 years. Females [Table 2] contributed to more than half of the fever cases.
Table 1: Age-wise distribution of suspected cases of dengue (n=64)

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Table 2: Sex distribution of suspected cases of dengue (n=64)

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Clinical features

The clinical presentation of the 36 suspected cases of dengue is presented in [Table 3]. Among them, there was only one case of dengue hemorrhagic fever and three cases of DF. There were no cases of dengue shock syndrome apart from the two deaths. All the suspected cases had a fever that lasted for an average of 2 days with or without chills and rigor. Majority of the suspected cases were suffering from myalgia. Around half of them complained of nausea, vomiting, and headache. On clinical examination, two of the suspected cases were found to have hepatosplenomegaly and rash was found in one of them, who also complained of melena. Blood pressure was noted and was found to be within the normal limits.
Table 3: Clinical presentation of “suspected” dengue fever/dengue hemorrhagic fever cases (n=36)

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Laboratory findings

The blood samples collected from the fever patients and the suspected dengue cases were transported to the Department of Microbiology on the same date and were tested for the presence of dengue IgM and NS1 antigen. Out of the 36 suspected cases of DF, the blood samples of 4 (11.1%) cases were found to be positive for both dengue IgM and NS1 antigen.

Laboratory findings showed leukopenia, thrombocytopenia of varying degrees, and an increase in liver enzyme values in the laboratory-confirmed cases.

Ecological factors

There was intermittent rainfall that started from the early weeks of July 2018. The average temperature during late July was moderate.

Entomological findings

Entomological observations and results were based on adult mosquitoes collected by suction tube method and aspirator torch in indoors in the houses during the daytime. Larval sampling was done using various indices such as house, container, and BI.

During the house-to-house visit, each team also examined water containers in almost all households. A total of 363 containers in 106 houses were examined for vector breeding in the containers. Out of this, we found the larvae of mosquitoes in 34 containers distributed over 28 houses. We also calculated the vector indices for dengue, i.e., HI, CI, and BI.







The HI came out to be 0.26, the CI was 0.093, and the BI was 0.32.

Containers such as tyres, plastic materials, earthen pots, overhead tank, and water coolers were searched thoroughly for mosquito breeding sites apart from the stagnant water in the runnel. The spot map [Figure 3] did not show any specific pattern, though, most of the fever cases were located nearby the runnel (nala), which had stagnant small water pools.
Figure 3: Spot map of village kelapur showing the distribution of the fever cases. The violet broken border demarcates the runnel (nala) that runs surrounding the village and consists of many stagnant water pools in it

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Prevention and control measures

A separate team from the district health office launched a robust control measure within the first 3 days of the onset of the first case of fever in the village. All the villagers were asked to use full sleeve shirts, use mosquito repellants and to use mosquito nets even during the day nap.

DDT spraying was started with the support of district National Vector-Borne Diseases Control Program[10] staff. Anti-larval measures constituted using Temephos and thermal fogging with potable fog generator using Malathion solution.

Health education sessions using IEC materials were conducted in groups, and health volunteers from the villages were identified who were trained to diagnose the fever cases and help in spreading health awareness message among the villagers. Administrative authorities were made aware of the disease and ways and means of preventing the same were also recommended.

Weekly dry day was initiated and maintained, where all the villagers drained their stored water and refilled them after 24 h.


  Discussion Top


Human beings get infected with dengue virus as a result of a bite of an infected mosquito. Aedes aegypti is the principal vector, which is a small, black and white, domestic mosquito. It prefers to lay eggs in artificial containers, which are found commonly in and around the households, for example, open water tanks, drums, stagnant water in vacant flower vases, old car tyres, coconut shells, etc. After an infective mosquito bites a person, the dengue virus undergoes an incubation period of 3–14 days, after which the person suffers from acute onset of the different signs and symptoms mentioned previously.[8]

There was a sudden out spurt of fever cases in a lapse of around 2 weeks. Thirty-six of them were found to have been suffering from DF, among which 4 of them were confirmed in the laboratory. The proportion of suspected cases was 56.2% (36 out of 64 fever cases), which is quite high, though only 11.1% (4 out of 36 cases) had laboratory confirmed dengue infection. The pattern of the outbreak was not found to be explosive, as only 6% of the total population was found to have been suffering from fever during the outbreak period. The houses having serologically confirmed cases were found adjacent to one another. In many families, multiple fever cases were also found.

One out of the four confirmed cases of the DF reported a history of travel in the last week before the onset of fever. Before the outbreak, no dengue cases were reported in the past 1 month from the village. IgM antibodies were found to be positive in all the four cases of DF that confirms the initiation of the spread of viremia.

The public health authorities were very prompt in action and initiated integrated vector control measures soon after the outbreak was declared in the village. They also initiated the vector control measures along with health awareness in the neighboring villages.


  Conclusion Top


In developing countries like ours, where vector-borne diseases are quite rampant, a technique like that of a rapid field epidemiological survey/investigation, though unfortunately not being implemented so often nowadays, would definitely help us to control an impending epidemic even today.

Acknowledgment

We duly acknowledge the support received from District Health Officer, District Epidemiological Officer and district health team of Wardha, Maharashtra, India, for conducting the field epidemiological investigation and dissemination of the findings.

Financial support and sponsorship

Nil.

Conflicts of interest

There are no conflicts of interest.



 
  References Top

1.
World Health Organization, Tropical Disease Research. Dengue: Guidelines for Diagnosis, Treatment, Prevention and Control. France: World Health Organization; 2009.  Back to cited text no. 1
    
2.
World Health Organization. First Report on Neglected Tropical Diseases: Working to Overcome the Global Impact of Neglected Tropical Diseases. Geneva: World Health Organization; 2010.  Back to cited text no. 2
    
3.
Government of India. National Guidelines for Clinical Management of Dengue Fever. New Delhi: Government of India; 2014.  Back to cited text no. 3
    
4.
National Centre For Disease Control, Directorate General of Health Services, Ministry of Health and Family Welfare. National Centre For Disease Control Annual Report 2016-17. New Delhi: Government of India; 2017.  Back to cited text no. 4
    
5.
Gupta N, Srivastava S, Jain A, Chaturvedi UC. Dengue in India. Indian J Med Res 2012;136:373-90.  Back to cited text no. 5
[PUBMED]  [Full text]  
6.
Paramasivan R, Thenmozhi V, Hiriyan J, Dhananjeyan K, Tyagi B, Dash AP. Serological and entomological investigations of an outbreak of dengue fever in certain rural areas of Kanyakumari district, Tamil Nadu. Indian J Med Res 2006;123:697-701.  Back to cited text no. 6
    
7.
Mishra R, Kumar P. A report on outbreak investigation of dengue in Bihar in 2015. J Med Sci Clin Res 2013;4:13557-68.  Back to cited text no. 7
    
8.
Park K. Park's Textbook of Preventive and Social Medicine. Vol. 24. Jabalpur, India: M/S Banarisadas Bhanot Publication; 2017. p. 391-4.  Back to cited text no. 8
    
9.
Department of Communicable Disease Surveillance and Response, World Health Organization. WHO Recommended Surveillance Standards. 2nd ed. Geneva: World Health Organization; 1999. p. 38.  Back to cited text no. 9
    
10.
National Vector Borne Disease Control Programme of India. Guidelines for Integrated Vector Management for Control of Dengue/Dengue Haemorrhagic Fever. New Delhi: National Vector Borne Disease Control Programme, Directorate General of Health Services, Ministry of Health and Family Welfare; 2015.  Back to cited text no. 10
    


    Figures

  [Figure 1], [Figure 2], [Figure 3]
 
 
    Tables

  [Table 1], [Table 2], [Table 3]



 

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