Dengue spread in Assam

Dengue fever (DF) and its severe forms, ‘dengue hemorrhagic fever’ (DHF) and ‘dengue shock syndrome’ (DSS), have become major international public health concerns. Over the past three decades, there has been a dramatic increase in dengue cases globally. Approximately 2.5 billion people live in dengue-risk regions, with about 100 million new cases each year worldwide. Dengue is endemic in India, with reported disease outbreaks in large metropolises. However, with increased urbanisation and population movement, the disease is reportedly spreading to other metropolitan areas or cities that were hitherto free from disease. Dengue is spreading rapidly and becoming established in Assam owing to socio-economic and developmental changes, including a dramatic increase in unplanned urbanisation, population movement, a lack of proper waste management, and inadequate vector control measures. It has affected a large population in the state for the past thirteen years. Assam reported 237 confirmed cases of dengue and two deaths for the first time in 2010. In 2011, it was recorded as nil. Subsequently, there was a significant increase in 2012 and 2013, with 1058 and 4526 cases recorded, resulting in five and two deaths, respectively. But it decreased in 2014, with 85 cases recorded. Again, there was a significant increase in 2015, 2016, and 2017, with 1076, 6157, and 5016 cases recorded and two, four, and two deaths, respectively. But it decreased in 2018, 2019, 2020, and 2021, with 166, 196, 33, and 103 confirmed cases of dengue with no deaths. But in 2022, dengue cases increased to 1826, with two deaths. Of the total confirmed cases for each year in Assam, the majority were recorded in Guwahati. Cases were reported mostly from those places where people harvest rainwater and often leave tyres, drums, and canisters out in the open. The actual disease burden is estimated to be much higher, with many cases undiagnosed and additional cases reported in the public and private sectors. Dengue is taking a turn this year in Assam, with close to 400 confirmed cases so far. Positive cases of dengue have been reported from Guwahati, Diphu, and different districts of the state. So far, there have been three confirmed dengue deaths in the state. Though it has not reached epidemic scale in Assam, there is a chance of more dengue cases this year. This needs the urgent attention of the government authorities. The authorities should launch a publicity campaign through different media to keep the public well informed. Proper information should reach the people on the dos and don’ts of dengue and improve their overall preparedness to meet any deterioration in the situation. Any laxity on the part of the authorities can easily lead to an epidemic-like situation in Assam, especially in Guwahati. Dengue infection is caused by any one of four types of distinct but closely related viruses, namely DV1, DV2, DV3, and DV4, of the genus Flavivirus that spread by the bite of an infected Aedes mosquito. The virus causes self-resolving dengue fever in the majority of cases, characterised by severe body aches, retro-orbital pain, headaches, and, at times, rash, abdominal pain, and nausea. In a small proportion of cases, the disease develops into the life-threatening DHF, resulting in bleeding, low levels of blood platelets, and blood plasma leakage, or into the DSS, where dangerously low blood pressure occurs. The WHO 2009 classification divides dengue fever into two groups: uncomplicated and severe. The diagnosis of dengue infection is routinely done by demonstration of anti-DV IgM antibodies or by NS1 antigen in patients’ serum, depending on the days of illness, using ELISA kits. Molecular methods like RT-PCR and DV isolation in tissue culture cells and their sequencing are also done. The treatment of acute dengue is supportive, using either oral or intravenous rehydration for mild or moderate disease and intravenous fluid and blood transfusion for more severe cases. In the absence of a vaccine, vector control is the primary means of controlling dengue infection. In Assam, dengue cases are reported during the post-monsoon period every year, with a peak between mid-August and November. During 2013, a rise in trend was seen early owing to an early monsoon. Initially restricted to urban areas, the occurrence of dengue infections has now spread to semi-urban and rural areas in Assam. The Kamrup (Metro) district and districts bordering Arunachal Pradesh are places mostly affected by dengue in Assam. Aedes aegypti and Aedes albopictus mosquitoes, which are the vectors of dengue, are reportedly prevalent in Assam and widely abundant in urban areas like Guwahati and suburbs. They breed in a wide variety of containers like empty car batteries, drums, and tyres where water can accumulate easily and are especially found in abundance in Guwahati. Open dumping of solid waste materials is common in the city, and this helps in the breeding of mosquitoes. Aedes aegypti is the most common species in Guwahati. The seasonal prevalence of both mosquito species occurs from the onset of rain in April until December. The transmission patterns of dengue are influenced by temperature and precipitation. Temperature affects egg viability, larval development, adult longevity, and dispersal, whereas rainfall affects the abundance and productivity of the breeding habitats of Aedes mosquitoes. A temperature range of 18–33.2 °C is considered ideal for the transmission of dengue fever. The favourable environment, high humidity (60–90 percent), warmer climates (22–33 degrees C) for most of the year, and excessive and prolonged rainfall in the state offer ideal conditions for the proliferation of these mosquito vectors and the spread of disease. With the increasing distribution range of Aedes aegypti and evidence of virus activity, it is projected that dengue will emerge as a major public health issue in Assam. There is a need for the identification of high-risk areas, vector incrimination, and seasonal infectivity of dengue so that future outbreaks could be avoided by targeted interventions. Surveillance for probable detection of dengue infections, monitoring of vector activity, and initiation of vector control measures should be ensured so as to prevent disease transmission in the high-risk zones. The control of Aedes mosquitoes in Assam is very challenging and requires community involvement. Destroying the breeding grounds of mosquitoes through an intense public campaign, proper solid waste disposal, improved water storage practices, including covering containers to prevent access to egg-laying female mosquitoes, supplying medicated mosquito nets in affected areas, protecting oneself from mosquito bites using clothes with long sleeves and mosquito repellent, and educating the people on the basics of health and hygiene are simple yet very effective ways of minimizing the impact of dengue in Assam.