Why India’s deadly dengue crisis is now no longer confined to the monsoons

Gurugram, India — When Nitin Sharma developed a precocious fever successful May, dengue was the past happening connected his mind.

The monsoon was inactive weeks away. Like galore Indians, the 32-year-old bundle technologist from Gurugram, a concern territory extracurricular New Delhi, had grown up believing dengue was a illness that arrived with the rains and disappeared erstwhile the monsoon play ended.

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So erstwhile headaches, terrible assemblage aches and fatigue forced him to sojourn a backstage infirmary successful Gurugram, helium assumed helium was suffering from a regular viral infection.

“I thought it would beryllium immoderate seasonal fever,” Sharma said. “Nobody successful my household adjacent considered dengue due to the fact that it wasn’t monsoon play yet.”

A humor trial revealed otherwise. Doctors diagnosed him with dengue fever.

For astir 2 weeks, Sharma remained distant from enactment arsenic weakness and fatigue persisted agelong aft the fever subsided.

“What shocked maine astir was the timing,” helium said. “Earlier, if idiosyncratic had a fever successful April, dengue would person been the past happening we thought about.”

Growing displacement successful illness pattern

Doctors crossed India accidental Sharma’s acquisition is becoming progressively common.

Hospitals successful respective states began reporting dengue infections weeks earlier the monsoon officially reached the confederate authorities of Kerala past week, reflecting what scientists picture arsenic a increasing displacement successful the behaviour of 1 of the country’s astir wide mosquito-borne diseases.

Health experts pass that rising temperatures, erratic rainfall and accelerated urbanisation are helping dengue-carrying mosquitoes past longer and dispersed farther than before, gradually transforming what was erstwhile considered a seasonal illness into a year-round nationalist wellness threat.

“Dengue is nary longer restricted to the post-monsoon period,” said Dr Harshdeep Joshi, prof and caput of Community Medicine astatine Maharishi Markandeshwar Medical College and Hospital successful Haryana.

“We are progressively seeing cases extracurricular the accepted season. The transmission model appears to beryllium expanding,” helium told Al Jazeera.

A dengue diligent rests nether a mosquito nett astatine the dengue ward of the government-run Tej Bahadur Sapru Hospital successful Prayagraj, Uttar Pradesh, India, connected October 13, 2022 [Rajesh Kumar Singh/AP]

For decades, dengue outbreaks successful India followed a comparatively predictable cycle. Cases would statesman expanding during the monsoon, highest successful the weeks aft dense rains and past diminution arsenic temperatures cooled.

That signifier is becoming little distinct. Even earlier this year’s monsoon play officially began, hospitals successful respective cities reported a emergence successful suspected dengue cases.

According to the National Center for Vector Borne Diseases Control (NCVBDC), India reported 6,927 dengue cases by the extremity of February, 2026.

Although this fig covers lone the archetypal 2 months of the year, it indicates unusually aboriginal transmission. For comparison, NCVBDC-linked figures cited successful a Frontiers successful Public Health survey amusement 6,837 cases were recorded during the full January–May play successful 2021, and 10,172 cases during the aforesaid play successful 2022.

This means that the 2026 fig has already exceeded the afloat January–May full of 2021 wrong conscionable 2 months and is rapidly approaching the early-season load seen successful 2022.

While not a cleanable like-for-like comparison, epidemiologists accidental the signifier is important due to the fact that dengue transmission successful India has historically remained debased betwixt January and May.

In caller years, however, that seasonal spread has narrowed.

The confederate authorities of Tamil Nadu accounts for the highest fig of infections this twelvemonth with 2,873 cases, followed by Maharashtra (786), Kerala (670) and Karnataka (560). Southern states consistently study higher aboriginal transmission owed to warmer climates, longer mosquito breeding windows, and successful immoderate cases, much extended diagnostic reporting systems.

Taken together, the information suggest that dengue transmission is opening earlier and spreading much persistently crossed the twelvemonth than successful erstwhile cycles.

Long-term inclination and nationalist burden

Official information amusement that dengue cases successful India person remained precocious successful caller years, with 289,235 infections and 485 deaths recorded successful 2023, the highest yearly load successful caller history.

In 2024, India reported 233,519 cases and 297 deaths, portion 121,824 cases and 131 deaths were recorded successful 2025.

A Bruhat Bengaluru Mahanagara Palike (BBMP) idiosyncratic sprays an country to eradicate mosquitoes successful Bengaluru, India, July 8, 2024 [Jagadeesh NV/EPA]

Public wellness experts accidental these fluctuations bespeak the cyclical quality of dengue outbreaks, wherever ample epidemic years summation population-level immunity to ascendant serotypes, temporarily reducing transmission successful consequent years. However, they caution that this does not contradict the semipermanent enlargement of dengue’s geographic and seasonal range, which continues to widen owed to clime variability, urbanisation and changing mosquito ecology.

Doctors accidental surveillance measures that usually statesman astir the rainy play present request to commencement overmuch earlier.

“We utilized to hole chiefly during the monsoon months,” said Dr SM Kadri, a nationalist wellness advisor and erstwhile surveillance serviceman successful Haryana. “Now hospitals and wellness workers person to stay alert astir passim the year.”

“The diminution seen successful 2025 should not beryllium interpreted arsenic a retreat of the virus. Dengue transmission successful India tends to fluctuate sharply twelvemonth to twelvemonth owed to a operation of colonisation immunity pursuing large outbreak seasons, changes successful circulating serotypes, and section biology conditions that impact mosquito breeding,” said Dr Aubair Hussain, a Srinagar-based physician.

He added that aft precocious transmission years, partial immunity successful affected populations tin temporarily trim lawsuit loads, but this does not interrupt semipermanent transmission trends.

“Rainfall distribution, somesthesia variations and municipality h2o retention patterns tin besides disrupt mosquito breeding successful definite pockets, which further contributes to these short-term drops,” helium said.

Climate, contamination and illness severity

A survey published successful Environmental Pollution (Elsevier) successful 2026 analysed dengue information from 20 endemic countries betwixt 2020 and 2024 and recovered a beardown relation betwixt semipermanent vulnerability to good particulate aerial contamination and higher dengue mortality.

The survey focused connected PM2.5 — good particulate substance tiny capable to penetrate heavy into the lungs and participate the bloodstream. It recovered that countries with higher levels of PM2.5 contamination recorded dengue decease rates 3 to 5 times higher than countries with cleaner air.

For context, the World Health Organization recommends an yearly PM2.5 vulnerability bounds of 5 micrograms per cubic metre, acold beneath the levels observed successful astir high-burden countries included successful the study.

The researchers besides recovered that aerial contamination remained an autarkic predictor of dengue severity adjacent aft controlling for income levels, colonisation density, rainfall, somesthesia and baseline wellness conditions, suggesting it whitethorn worsen illness outcomes done systemic inflammation oregon immune accent pathways.

“Long-term vulnerability to good particulate aerial contamination tin weaken immune and vascular systems, and successful dengue-endemic regions, this whitethorn importantly summation the severity and fatality of infections erstwhile combined with clime and socioeconomic stressors,” said Sakirul Khan, pb writer of the survey connected aerial contamination and dengue mortality.

Another survey published successful Scientific Reports (January 2025) recovered that dengue transmission successful India is powerfully influenced by changing clime conditions, peculiarly temperature, rainfall patterns and humidity.

Based connected information from Pune (2004–2015), the survey showed that temperatures supra 27 degrees Celsius (81F), humidity betwixt 60 and 78 percent, and moderate, evenly distributed monsoon rainfall make conditions that favour dengue spread.

It besides recovered that utmost rainfall tin trim transmission by flushing mosquito breeding sites. The exemplary projected a important emergence successful dengue hazard successful aboriginal decades nether clime alteration scenarios.

Vaccines being tested

India, meanwhile, is accelerating efforts to make preventive tools.

Earlier this year, the authorities approved Takeda’s dengue vaccine, Qdenga. Takeda is simply a Japanese multinational pharmaceutical institution headquartered successful Tokyo and 1 of the world’s starring vaccine developers. It has partnered with Biological E, a Hyderabad-based Indian vaccine manufacturer, for section production.

At the aforesaid time, the Indian Council of Medical Research (ICMR), the country’s apex biomedical probe body, and Panacea Biotec, a New Delhi-based biotechnology firm, completed Phase III objective proceedings enrolment for “DengiAll”, India’s archetypal indigenous single-dose dengue vaccine candidate, involving 10,335 volunteers crossed India.

A Phase III objective proceedings is simply a large-scale quality survey conducted to corroborate a vaccine’s effectiveness, show broadside effects and found information earlier regulatory approval.

The Serum Institute of India is besides conducting Phase III trials for its vaccine candidate, TetraVax-DV.

Researchers anticipation these efforts volition pb to an affordable vaccine susceptible of protecting against each 4 dengue serotypes — DENV-1, DENV-2, DENV-3 and DENV-4 — which are chiseled familial strains of the virus. All 4 serotypes co-circulate successful India, making multi-strain extortion captious to forestall reinfections and terrible disease.

But experts caution that vaccination unsocial volition not lick the problem.

“Even with an effectual vaccine, vector power and surveillance volition stay critical,” said Dr Gagandeep Kang, erstwhile prof astatine the Christian Medical College successful Vellore.

Kadri agreed, saying determination is “no azygous solution”.

“Vector control, sanitation, illness surveillance, nationalist consciousness and stronger healthcare systems each stay essential,” helium said.

Back successful Gurugram, Sharma says his unwellness has changed however helium thinks astir dengue.

He present keeps mosquito repellents astatine location passim the twelvemonth and regularly checks angiosperm pots, rooftop tanks and h2o containers for stagnant water, careless of the season.

“It feels similar the illness tin hap immoderate clip now,” helium said.