The story so far: In the past few weeks, cases of dengue have been rising in some parts of the country. Karnataka, in particular, has been experiencing a rapid surge in cases in the last few days, while the cases have been climbing up in Kerala and Tamil Nadu as well.
According to data published on the website of the National Centre for Vector Borne Diseases Control, the country has recorded 19,447 cases of dengue and 16 deaths till April 30, 2024. Going by this data, Kerala and Tamil Nadu accounted for the most number of cases; the former had 4,412 cases and 14 deaths and the latter registered 4,204 cases and two deaths. Karnataka, where cases are currently soaring, had, till then, recorded 2,503 cases and nil deaths. Maharashtra and Andhra Pradesh were the only other States with over 1,000 cases each.
Figures from the daily bulletin now being issued by Karnataka’s Department of Health and Family Welfare show that the State recorded a total of 7,840 cases of dengue and seven deaths from January 1 to July 10. Of this, Bruhat Bengaluru Mahanagara Palike recorded the most number of cases at 2,292. The active caseload in the State stood at 358. On July 10 alone, the State reported 293 cases.
What is the global situation of dengue?
According to the World Health Organization (WHO), as of April 30, over 7.6 million cases of dengue were reported in 2024. This included 3.4 million confirmed cases, over 16,000 severe cases and over 3,000 deaths.
In an update on the global scenario dated May 30, it said that 90 countries have known active dengue transmission, adding that “not all of which have been captured in formal reporting”. WHO pinpointed that the actual burden of dengue is underestimated as many endemic countries did not have strong detection and reporting mechanisms.
The WHO noted that at least five countries, including India, were grappling with the onset of monsoon season, which created suitable conditions for the breeding and survival of Aedes mosquito. Urbanisation and population movements have also played a pivotal role in the increasing burden in the region.
WHO observed that the incidence of dengue has grown dramatically around the world in recent decades. “About half of the world’s population is now at risk of dengue with an estimated 100-400 million infections occurring each year. Dengue is found in tropical and sub-tropical climates worldwide, mostly in urban and semi-urban areas,” it pointed out.
Dengue is endemic in more than 100 countries in the WHO regions of Africa, the Americas, the Eastern Mediterranean, South-East Asia and Western Pacific. The Americas, South-East Asia and Western Pacific regions were the most seriously affected, with Asia accounting for around 70% of the global disease burden. However, it also went on to note that dengue is spreading to new areas in Europe, the Eastern Mediterranean and South America.
How does dengue spread and how is it treated?
Dengue virus is transmitted to humans through the bite of infected mosquitoes, with the primary vector that transmits the disease being Aedes aegypti. While cases are mostly asymptomatic or mild, some may develop severe dengue that could include shock, severe bleeding or organ impairment. According to the National Guidelines for Clinical Management of Dengue Fever, an acute febrile illness of two to seven days duration with two or more of the following manifestations - headache, retro-orbital pain, myalgia, arthralgia, rash and haemorrhagic manifestations - were the clinical features of dengue fever. Clinical management of dengue fever may vary depending on the severity of illness. In those without any warning signs or complications, dengue is managed through symptomatic and supportive treatment.
What are the emerging patterns in dengue?
Researchers and public health experts have been closely monitoring the emerging patterns in dengue. While it remains a serious public health concern, surveillance, vector control, prevention of disease transmission, access to proper medical care, early and prompt diagnosis and appropriate management of cases are the much-needed focus areas.
Among the several factors associated with an increasing risk of dengue epidemics were changing distribution of Aedes aegypti vector, urbanisation and human activities fostering conducive environments for vector-host interaction and climate change-induced shifts in weather patterns, according to WHO.
In the article ‘Prevention and Control Strategies to Counter the Dengue Cyclical Trend in Tamil Nadu’, published in the Tamil Nadu Journal of Public Health and Medical Research, public health officials said that the first epidemic of clinical dengue-like illness was recorded in erstwhile Madras in 1780. Dengue virus was isolated in India during 1945 for the first time. The first evidence of the occurrence of dengue fever in the country was reported in 1956 from Vellore district in the State, they said.
Noting that dengue was once considered to be an arboviral disease of the urban environment infecting populations in municipalities, corporations and cities, they said the infection has spread to all geographic regions including rural and urban due to rapid increase in urbanisation, expanding travel patterns and climatic changes.
Tamil Nadu, they said, has witnessed outbreaks of dengue infection once in every five years in the past decade with the last outbreak occurring in 2017. With every outbreak, the prevalence has increased since 2008, the year when the first ever outbreak was noted, followed by 2012 and 2017.
