International Journal of Mosquito Research 2016; 3(4): 39-47 ISSN: 2348-5906 CODEN: IJMRK2 An outbreak investigation of dengue fever in the IJMR 2016; 3(4): 39-47 © 2016 IJMR coastal areas of Nagapattinam, Thiruvarur and Received: 07-05-2016 Accepted: 08-06-2016 Thanjavur districts in Tamil Nadu, India during G Praveen 2012 IDSP, National Centre for Diseases Control, 22-Shamnath Marg, Delhi, India G Praveen, BK Tyagi, Nirmal Joe and Manisha Bias Thakur B K Tyagi a) Visiting Professor, Punjabi Abstract University, Patiala, Punjab, An outbreak of dengue fever occurred in the coastal Nagapattinam and adjoining Thiruvarur and India Thanjavur districts of Tamil Nadu during late October-early November, 2012. An-depth investigation b) Scientist ‘G’ (Director) & was made into the reasons attributable to the spread of dengue in these districts, both urban and rural Emtd. Director in-Charge, Centre settings, between 23rd and 27th November, 2012. Till 22nd November a total of 299 cases and 2 deaths in for Research in Medical Nagapattinam district and 612 cases with 3 deaths in Thanjavur district were reported due to dengue. An Entomology (ICMR), 4-Sarojini increased trend in dengue cases was observed from September to November, with all the age groups Street, Chinna Chokkikulam, affected. High entomological indices along with eco-bio-socioeconomic factors such as unprecedented Madurai 625002, TN, India rainfall, construction sites, abandoned houses and boats, tyres and coconut shells were the major reasons for sudden abundance of Aedes mosquitoes. Robust monitoring and surveillance activities, along with Nirmal Joe Regional Office of Health & control measures, by the district authorities kept the disease spread under check by effectively Family welfare, Government of strengthening both case management and laboratory support, on one hand, and regularly organizing India, Chennai interactive co-ordination meetings at all levels to sensitize people through IEC and awareness programmes as well as source reduction of Aedes mosquito breeding. Manisha Bias Thakur Department of Medicine, Keywords: Dengue, outbreak, coastal districts, Nagapattinam, Thiruvarur, Thanjavur, Tamil Nadu Safdarjung Hospital, New Delhi, India Introduction During last two decades dengue, which has lately become a serious public health problem both geographically and in its intensity, emerged as the fastest spreading mosquito-borne viral [1, 3] infection in the world . It is an acute systemic viral disease that has established itself globally in both endemic and epidemic transmission cycles. Dengue virus infection in humans is often unapparent [4] but can lead to a wide range of clinical manifestations, from mild fever to potentially fatal dengue haemorrhagic fever (DHS) and dengue shock syndrome (DSS) [2]. The lifelong immunity developed after infection with one of the four virus types is type- specific [1, 2] and progression to more serious disease is frequently, but not exclusively, [2, 5] associated with secondary infection by heterologous types . Clinical features of dengue virus infection include fever, rash and joint pain [2, 3], which are however common in other certain febrile illnesses and may lead to misdiagnosis and interpretation. The diagnostic methods available also have limitations and a full complement of tests is not feasible in many healthcare points. Owing to the inherent problems related to definition of these diseases, on one hand, and, since dengue transmission comes in a wide variety of forms, with varying levels of spatial coverage and reliability, on the other, there has been differences in opinion of its global distribution which, considering varied estimates, seems to range from 30% [1] to 54.7% [2] of the world’s population (2.05–3.74 billion) from about 136 countries [1, 6]. Correspondence Ironically, though more than a century has elapsed when dengue virus was first discovered, B K Tyagi there is no effective antiviral agent yet existing to treat dengue infection, nor any licensed Visiting Professor, Punjabi vaccine is available against dengue infection [2]. Because the dengue treatment remains to be University, Patiala, Punjab, supportive, the only way to curb dengue transmission is to focus on the vector control, using India; Emtd. Scientist ‘G’ combinations of insecticides and biological control agents targeting Aedes mosquitoes and (Director) & Director in-Charge, [7] Centre for Research in Medical management of breeding sites . Entomology (ICMR), 4-Sarojini India is among the worst dengue-affected countries in the world, along with Brazil, albeit Street, Chinna Chokkikulam, significant under-reporting [1, 6]. During 2012, dengue resurged almost throughout the country Madurai 625002, TN, India but maximum cases and deaths were reported in Tamil Nadu where some of the coastal districts ~ 39 ~ International Journal of Mosquito Research were worst-affected [8]. Since this outbreak of dengue cases Material & Methodology occurred severely in those districts which were earlier hit by The worst-affected coastal districts, namely, Nagapattinam, the devastating tsunami during December 2004 and Thiruvarur and Thanjavur, were surveyed from 23rd to 27th government had initiated post-tsunami several re-habilitation November, 2012, along with several senior state and district and vocational schemes, it became all the more important to administrative and health officials, primarily to investigate comprehend the factors behind this upsurge of dengue cases in reasons attributing to the spread of dengue fever in coastal coastal districts [9] ! Tamil Nadu districts (Fig. 1). Fig 1: Map of peninsular India showing Tamil Nadu with districts ([Note the marked districts of Nagapattinam (#1), Thiruvarur (#2), and Thanjavur (#3)] which were surveyed both virologically and entomologically during a dengue outbreak in November, 2012. The following methodology was pursued: Observations & Results a) Discussion with District Collector and District Health Nagapattinam distric officials of Nagapattinam, Thiruvarur and Thanjavur (i) Demography, topography and climate districts. Nagapattinam district of Tamil Nadu is located on the shores b) Secondary data mining and analysis of the three districts. of the Bay of Bengal covering an area of 2715.83 sq. km. This c) Visit to hospitals, laboratories and affected villages in the coastal district of Tamil Nadu lies between 10.10° and 11.20° three districts. North latitudes and 79.15° and 79.50° East longitudes. d) Larval and adult collections were done using standard Nagapattinam district was carved out by bifurcating the procedures. The identification was made following the composite Thanjavur district. District Nagapattinam has a keys of Barraud (1936) and Puri (1962). population of 16,14,069 (as per the 2011 census) and is e) The vector incrimination was carried out following the divided in eight taluks, ten blocks and four municipality areas. standard method. The average maximum temperature during the summers remains around 35 °C. The relative humidity of district hovers around 60 to 65%. The average annual rainfall is around 1000mm, notwithstanding majority of precipitation hails during Northeast Monsoon, October-December (Fig. 2). ~ 40 ~ International Journal of Mosquito Research Fig 2: Mean annual rainfall (2009-2012) for Nagapattinam district. (ii) First-hand interaction with state and district health and Again on 24th November, to seek appraisal on the dengue administrative authorities scenario in the district with various containment measures To review dengue situation in the state of Tamil Nadu, undertaken by the District Health Authorities, an in-depth particularly the badly affected Nagapattinam, Thiruvarur and discussion was held at the district headquarters of Thanjavur districts, foremost an interactive meeting on Nagapattinam with Mr. Munusamy, District Collector and November 23, 2012, was held with the Health Secretary of Mrs. Asia Mariam, District Revenue officer, Dr P Kannan, Tamil Nadu, Dr. J. Radhakrishnan, IAS, joined by the Director Additional Director (Malaria & Filaria), Dr. V.A. Ralphselvin, of Public Health, Dr. Porkai Pandiyan, and other senior Deputy Director, Nagapattinam, Dr. S. Rajesekar, Deputy officials including Dr. Paranjothy, Director of Medical & Director, Health (On Dengue Special Duty), Dr. Gurunathan, Rural Services; Dr. P Kannan, Additional Director (Malaria & Joint Director Medical and Rural Health Services, Dr. Filaria); Dr. Kolandaiswamy, Additional Director (Primary Kathiresan, Chief Entomologist and Dr. Kumar, Senior Health Centre); Dr. Saravanan, Joint Director (VBCP); Dr. Entomologist at District Collectorate, Nagapattinam. Rukmanandhan Additional Director (Planning); Dr. Raju, Following observations emerged in the meeting: Additional Director (Medical); Dr. Kathiresan, Chief Even though signs of outbreak began in September, Entomologist and various other entomologists at DMS sporadic cases occurred since January (Table 2). complex, Chennai During the meeting the following Two deaths in children below 5 years of age were reported observation were made: from Nagapattinam block. A total of 10,096 cases and 62 deaths due to dengue were An increased trend in dengue cases was observed from reported in Tamil Nadu till 22nd November 2012, (Table September to mid October 2012 (Fig 2) 1). Block Nagapattinam, an urban setting, was mostly All the 32 districts were affected by dengue outbreak, affected (140 cases) having a population of 82,559 and however, Nagapattinam and Thanjavur