Behind the Mosquito Epidemic in Delhi

Every evening, Nidhi shuts closed all the doors and windows of her 13th-floor apartment, to save her family from the havoc of mosquitoes. The 48-year-old, who moved to Delhi’s Kidwai Nagar government quarters with her family after the pandemic, lives in one of the 4,800 self-sufficient ‘green units’ that started being built in 2014 by the National Building Construction Corporation, after the existing 2,331 government quarters in East Kidwai Nagar were razed.

Meanwhile, a semi-pakka jhuggi (shanty) in the Geeta Ghat slums of East Delhi is managed by Poonam, who migrated to Delhi after her marriage. The jhuggi–jhonpri or JJ cluster opposite the Geeta Colony Shamshan Ghat is nominally served by the Delhi Development Authority, and is one of 44 such JJ clusters in the city. Like Nidhi, every evening Poonam struggles to cook dinner for her family in a kitchen teeming with mosquitoes. It’s so bad, she says, “I can’t tell if it’s cumin or mosquitos in the dal.”

In the wake of the erratic monsoon of 2023, dengue and malaria cases have surged to record highs, according to data from the National Centre for Vector Borne Disease. The North, West and Najafgarh zones of the New Delhi Municipal Corporation recorded the highest number of dengue cases in the city. In the National Capital Region, the highest number of cases was reported in Indirapuram, followed by Ghaziabad.

The entry of mosquitos into the urban landscape here is not sudden. Nor is their health impact uniform across the city’s diverse hierarchies. But the unprecedented rains caused by global warming, along with water scarcity, breackneck urbanisation, and the ignorance of many, are speeding Delhi towards a mosquito epidemic.

While Nidhi can close her freshly constructed flat against the vectors (carriers) of dengue, malaria and chikungunya, Poonam in her jhuggi can’t. Still, Poonam and her neighbours say that a regular supply of electricity and water is more fundamental to them than a pakka house. This is the opinion of most women in the Geeta Ghat basti, and it is shared by Devi, name changed, who stays in a makeshift jhonpdi about ten minutes away from the Anand Vihar metro station, near Ghaziabad.

Devi’s basti has some 10 households living along an uncovered roadside drain. At dusk, their jhuggis are enveloped in dense smoke from burning egg cartons or cowdung. This DIY solution to repel mosquitos is used by almost all her neighbours. Every evening, Devi has her dinner, does the family’s laundry and puts her children to bed outside the jhuggi amidst the smoke.

As she enters inside to fetch drinking water, a thick swarm of mosquitoes force her back outside her own house. “Mosquitos enter the jhuggi from the open drain, eating our life!” she exclaims.

Devi, IP Extension

Nearby in Patparganj, shelter is one of the fundamental needs for Chhoti, a 58 year old widow living in a kaccha house by Swami Dayanand Marg. Her family locks their spot on the main road footpath to sleep every night as mosquitoes rack up the inside of their jhuggi. The breeze from the fast-moving night traffic helps keep the mosquitos from them as they sleep without even a fan. Having rested on the footpath for the past seven years, her spot is right by a police checkpost (naka) for a sense of safety.

Chhoti, IP Extension

When an entomological survey was conducted in March and April 2022 by trained Dengue Breeding Checkers of the South Delhi Municipal Corporation, their report concluded that the mosquito density in the capital had risen by 50% over the previous year. The Najafgarh zone recorded the highest mosquito density of 9.8 man per hour units, a measure of human exposure to mosquito bites. It also recorded one of the highest numbers of dengue cases this year.

Najafgarh has the largest open drain in Delhi, earlier called the River Sahibi. The river was widened for flood control. But soon after it was linked to the Yamuna, the Sahibi started degrading into a naala. Maintenance of the Najafgarh drain, and the other big drains in Delhi, is the responsibility of the Municipal Corporation, while the network of small roadside drains, like the one along Devi’s jhuggi in Indirapuram, is supposed to be maintained by the Public Works Department of the Government of Delhi.

The SDMC’s 2022 report may have made little difference to the middle-class residents of Delhi, who shut their doors and windows to keep out the mosquitoes. But for Delhiites like Poonam, Chhoti, Devi and their families, these mosquitos keep them from either enjoying a peaceful meal or sleeping in their own homes at night.

Delhi data from the NCVBD over the years

After 1996, the year 2015 recorded the worst dengue outbreak in the country (15,687 cases and 60 deaths). Then cases of both dengue and malaria started to drop over the years as a result of state and public interventions like surveying, fogging and spreading awareness about vector borne disease. It seemed the residents of Delhi were gradually heading away from the threat of VBDs.

The declining trend was however short lived, and the trends have completely reversed since 2021. Dengue and malaria cases rose during the pandemic and harsh lockdown but were sometimes confused with coronavirus cases due to co-infection and a growing reliance on rapid testing kits to detect dengue. However, cases of dengue show a clear increase in 2022, and more so in the first seven months of 2023. The pre-monsoon period this year also recorded a 40% rise in mosquito breeding sites across the capital, according to the MCD’s weekly report for April.

As the mosquito density rises, the threat of dengue and malaria has returned to haunt Delhi. While some have the means to protect themselves from mosquito bites, others can only rely on natural immunity. What is causing the sudden rise in mosquito density in Delhi? And where are the breeding spots of these vectors of disease?

Construction around the Najafgarh naala

The cases of dengue, chikungunya and malaria recorded in Delhi in the first seven months of 2023 were the highest for this period in the last five years. A spike in these cases from January to July means that mosquito prevalence is no longer seasonal. The ‘dengue season’ that used to affect public health from July to November is now a threat around the year, because of the changing weather patterns induced by global heating.

Unprecedented rain in the summers (like in Chandigarh) and warmer winters have made large areas susceptible to disease-causing mosquitoes year round. Unseasonal drizzles also fill up empty coolers, pits and containers with fairly fresh water. It doesn’t evaporate as fast due to growing humidity after the rains, nor can it seep into the earth in cities. These innumerable small water pits in the city become favoured breeding grounds for various mosquito species.

Dengue cases from January to July in the last 5 years

The MCD also cited global warming to justify the rise in mosquitoes in Delhi, in a circular issued in March last year that explains: “Unpredictable climate changes occurring globally are leading to the emergence of Vector-Borne Diseases around the year.” MCD health officer Dr L.R Verma also informed me that the rise in VBD cases is due to the unseasonal showers in March this year.

But there is another side to changing weather. Dr Himmat Singh, an entomologist working with the National Centre for Malaria Research, wrote in a paper that the “dependency of dengue cases on climatic factors has revealed that there is a lag phase between rains and appearance of cases, which provides an opportunity to programme managers to carry out vector control measures along with source reduction.”

In other words, there is a sufficient window for civic bodies to predict and lower the incidence of VBDs, even in the face of sudden short showers in the city.

The untimely rains are coupled with the constantly warming temperature in Delhi. The dengue-carrying Aedes species of mosquito thrives best in temperatures of 25–39 degrees Celsius, a wide enough range for Delhi to host mosquitoes throughout the year. The expansion of Aedes species from the arid Thar desert to the upper Himalayas also shows the geographical evolution of dengue vectors as human activity changes the weather. Other global megacities too, like Mexico City and Bogota, were once considered immune to mosquitos, but have now developed a climate warm enough for the nuisance Culex species of mosquito at least.

In these urban areas structures like roads, buildings and pavements absorb the sun’s heat and re-emit it with greater intensity than natural surfaces like water, bushes and trees. This creates a warm island enclosing the cities, which have a slightly warmer temperature than surrounding rural areas. This ‘urban heat island effect’ also favours the breeding of the dengue-causing species Aedes aegypti.

Dr Himmat Singh of the NCMR further told me that the rise of mosquitoes in cities can be linked to diverse factors like water scarcity, urbanisation and civil construction.

“In urban areas, you have restricted all the land for residential or civil construction, which does not allow other species of insects and animals to exist together. Rural areas have natural spots where some species of fish and frogs feed on mosquitoes and keep their population under check,” he explained.

Without thought to green and blue spaces for other species, “Urbanisation has accelerated the growth of mosquitoes. The entire life cycle of Aedes mosquitoes has adapted to the anthropogenic activities of the urban population.”

Delhi sprawling urban landscape is predominated by artificial structures over nature. This creates more breeding sites for mosquito species that prefer urban spaces. Construction sites are among the most preferred breeding spots for malaria-causing Anopheles, Culex and sometimes Aedes mosquitos.

Although the NCVBD issued guidelines on construction sites ten years ago, including the need to amend building bye-laws to curb mosquito breeding while buildings are under construction, so far the laws only require building owners to gain a ‘Completion Certificate’ relating to fire safety and other regulations, as per the Unified Building Bye Laws (UBBL) of 2016.

In 2021, when VBD cases suddenly increased, more new regulations were released by the office of Delhi’s Lieutenant Governor. These regulations state that the‘Occupancy Certificate’ will only be granted to newly constructed buildings with anti-mosquito structures. However, the modified certificate is not compulsory for buildings that are already occupied, with the regulations yet to be made part of Delhi’s building by-laws.

Then in 2022, drones were deployed by the MCD to check for breeding spots at building construction sites. Fines of up to 5,000 Rs were levied on corporate and government constructions like an L&T site on Bhairo Marg, a Reliance construction site, a Delhi government dispensary in Dwarka, a government school in Hari Nagar, and a Shapoorji Pallonji construction site at the ITPO complex. In just the week from May 2–6, “168 construction sites and 25 government offices” were found hosting larval breeding sites for Aedes mosquitoes. Mosquito breeding at construction sites has figured prominently on the MCD radar this year too.

Besides large constructions, from the new Parliament building and Central Vista to the convention halls for the G20 conference, the capital city is also home to an estimated 200 thousand dishoused people, and in terms of civic infrastructure, no fewer than 1300 manmade drains stretching up to 1700 km, according to data from the Ministry of Housing and Urban Affairs. The Delhi government further estimates that there are 6,343 slums home to 10.2 lakh households in tiny boxes, apart from a variety of posh colonies. This composition calls for a nuanced understanding of the relationship between mosquito breeding sites and the city’s diverse landscape of inequality.

Last March, former Union Health Secretary Rajesh Bhushan in a speech pointed to the Ministry of Housing and Urban Affairs, one of the important stakeholders in the fight against mosquitoes:

“There is this ‘Smart City’ intervention because of which there is a lot of civil construction. The huge amount of civil activities in terms of digging up huge areas, in terms of construction material getting staged, mud, sand, bricks, steel. Thus, more potential for water to collect and form more breeding grounds for all kinds of vectors. Why only dengue? What is it that we are doing to sensitise our urban local bodies in this sense? A very frank answer would be, not much!”

Bhushan also noted that structural and engineering failures in toilets and water storage facilities in rural areas were aiding the spread of vector-borne disease. Though it is true that development has a lot to do with structures like buildings, basements, slums and naalas, development such as urbanisation has a lot more to do with the people of the cities. And it turns out that mosquitoes have not only evolved to adapt to urbanisation but also with the urban habits of people living in the cities.

Part 2 follows