Special report: Why is India seeing a massive dengue outbreak this year?

When Dr Shaukat Kalam visited Firozabad in Uttar Pradesh in August, he saw signs of a deadly dengue outbreak everywhere. “We found mosquito breeding in every second house, in the garbage, on the roadside, in articles where water was accumulating,” said the entomologist, an expert on insects, who currently works with the central government’s National Vector Borne Disease Control Programme.

Dengue is a viral infection that spreads through the bite of the Aedes aegypti mosquito. It causes fever, body ache and weakness. In severe cases, it can lead to a drop in platelets that help in blood clotting – this can trigger life-threatening complications.

While dengue is not uncommon in India, this year, several states in northern and central India have seen a sharp rise in cases. Nowhere more than in Uttar Pradesh, where over 29,000 cases had been recorded by the state directorate of health services, as of December 2 – two and a half times the number reported in 2019, the last year there was a spike in cases in the state.

In some districts in the state, cases have virtually exploded. For instance, Firozabad, a district in western Uttar Pradesh, recorded less than 100 cases of dengue annually in 2019 and 2020. This year, that number has jumped to 5,754 cases.

Not only are the number of cases higher, the disease has a wider geographical spread. All 75 of Uttar Pradesh’s districts have reported cases this year, up from 71 districts in 2018. In Firozabad, chief medical officer Dr Dinesh Kumar Premi said dengue cases have been found in 75% of villages and towns in the district this year. “We haven’t seen this kind of spread before in Firozabad,” he said.

National data suggests that the total number of dengue cases is lower this year than in 2019. According to a response by the health minister to a question in Parliament, India has recorded 1.64 lakh dengue cases this year, compared to 2.05 lakh cases in 2019.

But some doctors say that a large number of cases this year might have escaped the official count because of a growing reliance on rapid testing kits to detect dengue. While large laboratories use the ELISA test and report all positive cases to the government’s Integrated Disease Surveillance Programme, small clinics prefer to conduct a rapid test, called NS1 Antigen test, which gives results within 10 minutes. “Since this year there were so many dengue cases, most doctors did rapid tests for quick results. Not everyone reports the result to the local health department,” said Dr Siddharth Lalitkumar, a physician in Mumbai.

Some doctors, however, argue that, in fact, more cases are likely to have been detected this year because of the predominance of a particularly virulent strain of the disease, known as DEN2. “We saw more DEN2 serotype this year,” said Dr Amitabh Parthi, director, internal medicine in Fortis Memorial Research Institute, New Delhi. “Since it causes more severe infection, we saw an increased hospitalisation rate.” He added that between 15% and 20% of his dengue patients needed hospitalisation.

Regardless of whether this year saw a more serious spike in dengue cases than 2019, what is undeniable is that nationally, the footprint of dengue has been growing in the past decade. This was detailed in a paper published in the June edition of the journal The Society of Medical Anthropology, whose lead author was Dr Kalpana Baruah, the head of the dengue division in the National Vector Borne Disease Control Programme. The paper noted that while, in 2000, eight states and union territories in India reported dengue cases, by 2019, the disease was found in as many as 35 states and union territories, with an eleven-fold rise in the total number of cases.

Poor vector control in Uttar Pradesh

Numbers aside, experts believe the ground conditions in India this year have been conducive to a dengue outbreak – the country has seen a prolonged monsoon season, which allowed more breeding sites for mosquitoes. “We had high humidity this year,” said Kalam, a joint director in the National Vector Disease Control Programme, adding that mosquitoes survive longer during rainfall.

But it isn’t just nature that is responsible for the spread of the disease: experts say unplanned urbanisation in India is making it easier for mosquitoes to breed. And states like Uttar Pradesh are further exacerbating the crisis by neglecting timely mosquito-control measures.

It is instructive to compare Uttar Pradesh’s mosquito-control protocol with the one followed by the city of Mumbai.

While Uttar Pradesh begins the annual exercise of detecting and destroying mosquito-breeding sites – known as “source reduction” – after the arrival of monsoons in July, similar measures start as early as January in Mumbai. Between January and May this year, the municipal corporation of Mumbai inspected 41.14 lakh houses and found mosquito breeding in 12,807 sites, data from the insecticide department shows.

Mumbai has regular staff to tackle mosquito-breeding sites. But Uttar Pradesh relies solely on contractual staff hired during the monsoon.

This year, Uttar Pradesh hired around 1,700 domestic breeding checkers on contract to find mosquito breeding sites in houses and rooftops, said Dr Vikas Singhal, joint director in the directorate of health services. This effectively means there was one breeding checker for a staggering 1.4 lakh people.

District authorities in Uttar Pradesh recognise the need to make improvements. Firozabad’s chief medical officer Dr Dinesh Kumar Premi, for instance, said there is a need to begin the mosquito-control exercise from March.

But, at the state level, Singhal defended Uttar Pradesh’s mosquito-control protocol – since there is no rainfall between January and June, he argued, the number of breeding sites is low, and hence, domestic breeding checkers are not required.

It is precisely the cumulative impact of several years of such poor vector control that leads to a large-scale dengue outbreak, said Dr RS Sharma, a former additional director in the National Vector Disease Control Programme, who worked on bringing previous outbreaks under control, before he retired in 2017.

“We call this a blackout in surveillance,” he explained. “When vector control is stringent, the mosquito population is in check. When not stringent, slowly the mosquito population grows in a particular area, year after year.”

“For instance, 10 mosquitoes in a colony will increase to 100 in a year,” he said. “And when one mosquito is infected by dengue, the outbreak becomes suddenly difficult to contain.”

Sharma added that typically, an area will see a steady year-on-year rise in mosquito population, resulting in dengue cases peaking every three or four years.

There are other factors particular to this year that may have further impacted mosquito-control measures. Local vector control staff in Kanpur district said they were diverted for Covid-19 duty during the second wave in the summer, thus pushing mosquito control further down the priority list.

Kanpur saw not only a rise in dengue cases this year, but also an outbreak of Zika, another mosquito-borne disease, in October. On the ground, when Scroll.in visited the city in November, locals widely complained of poor sanitation in the city. In the residential colony of Adarsh Nagar, a swamp had become a breeding ground for mosquitoes until the Zika outbreak forced the municipal corporation to drain the stagnant water and remove the garbage dumped there.

According to Premi, the situation was also exacerbated by the city’s poor tap water supply – locals would store water in open drums at home, which became common mosquito breeding sites.

Municipal staff admitted that they were thinly stretched. Santosh Kumar Verma, an insect collector employed by the Kanpur municipal corporation, who collects mosquitoes for laboratory testing, said, “When the outbreak began, 100 contractual breeding checkers were deputed by the district. We need them on a permanent basis, not just for a few months.”

Kanpur is Uttar Pradesh’s largest industrial city. Despite that, its municipal corporation is inadequately staffed. As the predominantly rural state urbanises, the challenge of keeping mosquito-borne diseases like dengue under check is likely to become even steeper.

Unplanned and rapid urbanisation

Dengue cases in India were first detected in 1921. The disease was then limited to cities, a paper published in 1999 by the Regional Medical Research Centre of the Indian Council of Medical Research states. “Urbanisation and industrialisation tend to increase the numbers of habitats suitable for Aedes aegypti,” it notes.

A century later, the same pattern prevails. The research paper published in June this year, co-authored by Baruah, found a distinct correlation between the number of dengue cases and the level of urbanisation in an area.

“Vector-borne infections come when we see unplanned expansion of towns into cities,” said Pankaj Joshi, Principal Director of the Urban Centre Mumbai. While villages in India are converting into towns, and towns into smaller cities, their sewage, sanitation and infrastructure are not being upgraded as they need to be, he said.

This strain is visible on the ground in Uttar Pradesh. When Singhal, the joint director in the state directorate of health services, visited Firozabad, like the entomologist Kalam, he too found indoor mosquito breeding in unused coolers, fridges, water drums and plates underneath potted plants. Indeed, data from the office of the Firozabad chief medical officer states that mosquito breeding was observed in 42% of the houses.

The Aedes mosquito does not lay eggs in open drains with flowing water; rather it lays eggs in stagnant water accumulated in solid articles, whether in drains, garbage piles, or within homes.

“That can be prevented once residents are made aware of where a mosquito lays its eggs and how to prevent it,” Singhal said. But what worried him was that even municipal staff in Firozabad did not know this.

Firozabad district has seven municipal corporations and 806 villages. Premi, who was transferred to the district as chief medical officer in September to control the dengue outbreak, said he immediately began working with the municipal corporation in Firozabad city to streamline the disposal of solid waste and the clearing of drains to prevent water accumulation, as well as to launch a house-to-house survey to destroy mosquito breeding. But he found it difficult to tackle the situation in the district’s small towns and villages.“There is very little budget for vector control in rural areas,” he said.

Even towns lack proper planning. A report on urbanisation in India by the government think-tank, Niti Aayog, released in September this year said that “about 52% of the statutory towns and 76% of the census towns do not have any master plans to guide their spatial growth and infrastructural investments”.

“Such severe lack of preparedness to manage the level of urbanisation that the Indian cities are bound to witness in the coming decades is a huge risk,” the report said.

India is expected to have 25,000 new cities by 2030, according to Joshi, the executive director of the Urban Development Research Institute. “Unless sanitation and health infrastructure is in sync,” he said, “we will continue to see such outbreaks.”

Intermittent and prolonged rainfall this year

Since urbanisation is a gradual process, it cannot alone explain the huge jump in dengue cases this year. What made for a perfect storm this year, experts said, was the rainfall pattern.

Data from the Indian Meteorological Department shows that the country recorded a delayed withdrawal of the south-west monsoon this year – the second time in four years. Normally, the monsoon withdraws by the end of September. This year, the date extended to October 25. Between October and November, 43% districts in India experienced excess rainfall.

Experts blame the prolonged rainfall this year for the increased vector population. States reporting a high number of dengue cases – Uttar Pradesh, Madhya Pradesh, Punjab – all saw higher than normal rainfall this year.

In Madhya Pradesh, where 11,354 dengue cases had been recorded till the end of October, 10 districts received excess rainfall during the monsoon season. In Punjab, where over 16,000 dengue cases have been recorded so far, 19 districts received excess rainfall between October and November.

“Even parts of Maharashtra saw rainfall in the days around the festival of Diwali, which is unheard of,” said state epidemiologist Pradeep Awate.

Not only was the monsoon season prolonged, even the pattern of rainfall encouraged mosquito breeding. Dr Sher Singh Kashyotia, former additional director in the National Vector Borne Disease Control Programme, said this year the rainfall was largely intermittent – rain followed by a dry spell. “The Aedes mosquito breeding relies on water, humidity and warm temperature. A dry spell after rainfall provides warm temperature, conducive for mosquito breeding,” he said.

In contrast, heavy spells of rain can actually wash away larvae to some extent and reduce breeding, according to some studies.

What the future holds

With the winter setting in, health officials across the country are hopeful that the drop in temperatures will soon reduce mosquito breeding. But experts said that while winter usually spells the end of the mosquito proliferation, continuing rainfall in some parts of the country threatens to extend the dengue season. “We can expect dengue circulation to be prolonged,” epidemiologist Dr Harinder Ratti said.

Even if the current outbreak is brought under check, the long-term prognosis for the country does not look good, experts noted, given India’s lack of preparedness for both urbanisation and climate change. To avoid dengue outbreaks, the country needs to increase public awareness and create better municipal services to prevent mosquito breeding sites.

Another area where India could do better, experts said, is in strengthening the scientific apparatus for vector control. The National Vector Borne Disease Control Programme, the country’s premier scientific body to manage mosquito-borne disease outbreaks, is understaffed. It has 19 regional centres across India, each with a post for an entomologist. Currently, 18 posts are vacant. Kalam, who is posted in Lucknow, is the only regular entomologist across the 19 centres.

“An entomologist studies the vector population in an area, and can predict a possible outbreak as well as point out how to contain it by studying the vector burden in a region,” Kalam said. In the absence of such trained scientists, “there is nobody to guide and monitor vector control exercise,” he added.

Not just in the regional centres, even key posts in the organisation’s headquarters at New Delhi are lying vacant. The current head of the dengue and Zika division, Dr Kalpana Baruah, is a retired official who has been appointed as a consultant. She declined comment for this story.

“We are relying on consultants and contractual staff. What we need is fresh appointments,” a senior official said.

This reporting was supported by a grant from the Thakur Family Foundation. Thakur Family Foundation has not exercised any editorial control over the contents of this article.