Cases of dengue have been rising in several parts of the country. The country has recorded 35,000 cases of dengue and around 35 deaths this year. Kerala and Tamil Nadu have accounted for the most number of cases; the former with over 4,500 cases and 15 deaths and the latter registering around 4,300 cases and two deaths. Karnataka, where cases are currently soaring recorded over 2,600 cases. Maharashtra and Andhra Pradesh have repoited over 1,000 cases each.
As cities across India report a surge in dengue cases, a record number of cases have been reported around the world too, with Brazil and other South American countries worst affected. Data from the World Health Organization (WHO) show that the number of dengue cases has been increasing year-on-year.
More than 12 million cases and 6,991 deaths have been recorded globally till August this year, according to data from the WHO’s global dengue surveillance. This is more than double the 5.27 million cases recorded in all of last year, which itself was a record. Prior to last year, over the past decade, around two to three million annual cases of dengue had been reported at best.
Over the past two decades, there has been a “tenfold increase in reported cases” and “even this figure is likely an underestimate”, says a Lancet study. This is because not all countries — including India — report their data to the global surveillance network. Even among countries which report the data, not every dengue patient might have been tested and reported to the health authorities. Dengue is the “only infectious disease for which annual mortality is rising”.
India had seen an almost 50% rise in the number of dengue cases reported this year, as compared to the same period in 2023. Notably, India is also witnessing an increase in the geography of the infection. The disease spread from only eight states and Union Territories in 2001 to every single state and UT in 2022, with Ladakh reporting the first two cases that year.
The disease can spread more quickly in urban areas with a dense population providing ample breeding grounds to the Aedes aegypti mosquito. An increase in cases is generally reported during and just after the monsoon.
An increase in temperatures also allows mosquitoes to breed in places where they previously could not — in higher altitudes for instance. Global warming has definitely led to an increase in the prevalence of the vector in geographies it might previously not have been found. Moreover, climate change has also led to the virus becoming more robust and transmitting better.
The global movement of people and goods has increased over the years and this has led to a greater spread of infections. However, better testing and reporting might also add to the “increase”. Apart from dengue, other infections such as chikungunya and zika, which are also transmitted by the same vector, have also been on the rise. Zika was first reported in India in 2016 but there have been several outbreaks since then.
People need to ensure that mosquitoes do not breed at their homes, or in their neighbourhoods. Collection of water in pots, planters, bird baths, etc. need to be prevented. They also need to protect themselves against mosquito bites. The Aedes aegypti mosquitoes bite during the day — wearing clothes which cover the entire body, especially during the monsoons, can prevent bites. Public health systems also need to be robust in vulnerable countries or regions. It needs to focus on surveillance and prediction of outbreaks. This will help reduce the number of cases, and consequently deaths due to the infection.
WHO recommends two vaccines: Sanofi’s Dengvaxia and Takeda’s QDenga for dengue. However, these have not received approval in India. India itself is working on several vaccines like Serum Institute of India’s vaccine candidate developed using a genetically engineered weakened virus from the National Institute of Allergy and Infectious Diseases in the United States. Another candidate using the same virus is being developed by Panacea Biotec.
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