Faced with a shortage of entomologists, a trickier vector, increased travel, and less than optimal public participation to prevent its spread, the infection geography of dengue, which was restricted to eight States in 2001, currently covers all the States and Union Territories in India. Dengue has now breached the country’s last bastion, Ladakh (with two cases in 2022), senior health officials said.
As the country gets ready to welcome the southwest monsoon, which is associated with the rise of certain diseases, including malaria, dengue and Zika, the Indian Council of Medical Research (ICMR) confirmed that dengue’s infection geography has grown. “During the last two decades, there has been significant geographical spread of dengue with 11-fold increase and repeated outbreaks. The number of States and Union Territories reporting cases increased from eight in 2000 to all. Rural areas contributed approximately 32% of the total cases in 2015-16 and have increased to 41%-45% now,’’ experts maintained.
The dengue virus is transmitted by female mosquitoes, mainly of the species Aedes aegypti and to a lesser extent, Aedes albopictus. These mosquitoes are also vectors of the chikungunya, yellow fever and Zika viruses.
In India, Zika grew from miniscule numbers in Gujarat and Tamil Nadu and is now being reported from 11 States (Punjab Rajasthan, Gujarat, Madhya Pradesh, Uttar Pradesh, Delhi, Maharashtra, Kerala, Jharkhand, Telangana and Tamil Nadu). The World Health Organization estimates the global incidence of dengue has grown over recent decades, with half of the world population now at risk.
The ICMR said that this risk due to dengue, which is now endemic in more than 100 countries, has been propelled by several factors, including climate change, increased urbanisation (where environments are temperature controlled), and increased travel. But what is aiding mosquitoes in becoming the newest resilient urban pest?
Himmat Singh, from the ICMR-National Institute of Malaria Research, notes that the problems in the control of Aedes borne disease are manyfold. “Day biting habit, multiple biting, long incubation period, fast transport, eggs retained up to one year, container breeding, human environment, and intermittent water supply and poor waste management at construction sites add to the problem,’’ Dr. Singh said.
According to the Central government’s paper on dengue outbreaks in India, the dengue vector is very different from the malaria vector and so, bio-environmental strategies alone will not work. This, coupled with the shortage of entomologists in the country, works to help the spread of dengue.
ICMR officials said that besides the work on vaccines, they were also looking at increasing awareness and promoting prevention, people’s participation, and the use of the latest technology, including satellite imaging and drones to map vulnerable areas.