Dengue in India No Longer Seasonal: Experts Warn of Year-Round Health Threat
Theo Tauseef Ahmad, Sajid Raina (Al Jazeera)
Health experts warn that climate change, urbanization, and air pollution are turning dengue into a year-round health threat in India, extending far beyond the traditional monsoon window. Official data shows cases already spiking before the rainy season, with southern states hardest hit. Scientists link rising transmission to warmer temperatures, humidity, and air pollution, while India pushes forward with multiple vaccine candidates.
Gurugram, India — When Nitin Sharma developed a high fever in May, he never suspected dengue. The monsoon was still weeks away. Like many Indians, the 32-year-old software engineer grew up believing dengue only came with the rains.
But a blood test confirmed he had the dengue virus. Nearly two weeks after the fever subsided, he still felt weak and fatigued. “What shocked me most was the timing,” Sharma said. “Earlier, if someone got a fever in April, dengue was the last thing we thought of.”
Doctors across India say Sharma’s case is becoming increasingly common. Hospitals in several states have reported infections weeks before the official monsoon start.
“Dengue is no longer confined to the post-monsoon period,” said Dr. Harshdeep Joshi, Head of Community Medicine at Maharishi Markandeshwar Medical College Hospital in Haryana. “We are increasingly seeing cases outside the traditional season. The transmission window appears to be widening.”
For decades, dengue outbreaks in India followed a relatively predictable cycle: cases rose during the monsoon, peaked after heavy rains, and subsided as temperatures dropped. That pattern is becoming less distinct.
According to the National Vector Borne Disease Control Programme (NCVBDC), India recorded 6,927 dengue cases by the end of February 2026. This already exceeds the total for January–May 2021 (6,837 cases) and is approaching the early-season burden of 2022 (10,172 cases). Epidemiologists call this remarkable because dengue in India historically remained low between January and May.
Tamil Nadu in the south has the highest tally this year with 2,873 cases, followed by Maharashtra (786), Kerala (670) and Karnataka (560). Southern states have always had higher early-season transmission due to warmer climates and longer mosquito breeding periods.
Official data show India’s dengue caseload has remained high in recent years, with 289,235 infections and 485 deaths in 2023 — the highest annual burden in recent history. In 2024, India reported 233,519 cases and 297 deaths; in 2025, 121,824 cases and 131 deaths.
Public health experts say these fluctuations reflect the cyclical nature of the disease. “The decline in 2025 should not be interpreted as the virus retreating,” said Dr. Aubair Hussain, a physician in Srinagar. “After high-transmission years, partial immunity in the population can temporarily reduce the case load, but this does not disrupt the long-term transmission trend.”
A study published in Environmental Pollution in 2026, analyzing dengue data from 20 endemic countries between 2020 and 2024, found a strong link between long-term exposure to fine particulate matter (PM2.5) and dengue mortality. Countries with high PM2.5 levels recorded three to five times higher dengue mortality rates than cleaner-air nations.
Another study in Scientific Reports (January 2025) found that temperatures above 27°C, humidity of 60–78%, and moderate, evenly distributed seasonal rainfall create favorable conditions for dengue transmission. Predictive models suggest dengue risk will increase significantly in coming decades due to climate change.
On the solution front, earlier this year the Indian government approved Takeda’s Qdenga vaccine. The Japanese drugmaker has partnered with Biological E in India for domestic production. Meanwhile, the Indian Council of Medical Research (ICMR) and Panacea Biotec have completed enrollment of 10,335 volunteers for Phase III clinical trials of the indigenous vaccine “DengiAll.” The Serum Institute of India is also conducting Phase III trials for TetraVax-DV.
However, Dr. Gagandeep Kang, former professor at Christian Medical College in Vellore, warned: “Even with an effective vaccine, vector control and surveillance remain critical.” Echoing the sentiment, Dr. SM Kadri, former surveillance officer in Haryana, said there is no “single solution”: “Vector control, sanitation, disease surveillance, community awareness, and a stronger healthcare system — all are necessary.”
Back in Gurugram, Sharma said the illness changed how he thinks about dengue. He keeps mosquito repellent in the house year-round and regularly checks flower pots, rooftop water tanks and containers for standing water — regardless of the season. “It seems the disease can strike at any time,” he said.
