Why India’s deadly dengue crisis is now no longer confined to the monsoons
Experts warn that rising temperatures, erratic rainfall and rapid urbanisation are transforming a seasonal disease into a year-round public health threat. Gurugram, India — When
Experts warn that rising temperatures, erratic rainfall and rapid urbanisation are transforming a seasonal disease into a year-round public health threat. Gurugram, India — When Nitin Sharma developed a high fever in May, dengue was the last thing on his mind. The monsoon was still weeks away. Like many Indians, the 32-year-old software engineer from Gurugram, a business district outside New Delhi, had grown up believing dengue was a disease that arrived with the rains and disappeared once the monsoon season ended. So when headaches, severe body aches and fatigue forced him to visit a private hospital in Gurugram, he assumed he was suffering from a routine viral infection. “I thought it would be some seasonal fever,” Sharma said. “Nobody in my family even considered dengue because it wasn’t monsoon season yet.” A blood test revealed otherwise. Doctors diagnosed him with dengue fever. For nearly two weeks, Sharma remained away from work as weakness and fatigue persisted long after the fever subsided. “What shocked me most was the timing,” he said. “Earlier, if someone had a fever in April, dengue would have been the last thing we thought about.” Growing shift in disease pattern Doctors across India say Sharma’s experience is becoming increasingly common. Hospitals in several states began reporting dengue infections weeks before the monsoon officially reached the southern state of Kerala last week, reflecting what scientists describe as a growing shift in the behaviour of one of the country’s most widespread mosquito-borne diseases. Health experts warn that rising temperatures, erratic rainfall and rapid urbanisation are helping dengue-carrying mosquitoes survive longer and spread farther than before, gradually transforming what was once considered a seasonal disease into a year-round public health threat. “Dengue is no longer restricted to the post-monsoon period,” said Dr Harshdeep Joshi, professor and head of Community Medicine at Maharishi Markandeshwar Medical College and Hospital in Haryana. “We are increasingly seeing cases outside the traditional season. The transmission window appears to be expanding,” he told Al Jazeera. For decades, dengue outbreaks in India followed a relatively predictable cycle. Cases would begin increasing during the monsoon, peak in the weeks after heavy rains and then decline as temperatures cooled. That pattern is becoming less distinct.
Even before this year’s monsoon season officially began, hospitals in several cities reported a rise in suspected dengue cases. According to the Center for Vector Borne Diseases Control (NCVBDC), India reported 6,927 dengue cases by the end of February, 2026. Although this figure covers only the first two months of the year, it indicates unusually early transmission. For comparison, NCVBDC-linked figures cited in a Frontiers in Public Health study show 6,837 cases were recorded during the entire January–May period in 2021, and 10,172 cases during the same period in 2022. This means that the 2026 figure has already exceeded the full January–May total of 2021 within just two months and is rapidly approaching the early-season burden seen in 2022. While not a perfect like-for-like comparison, epidemiologists say the pattern is significant because dengue transmission in India has historically remained low between January and May. In recent years, however, that seasonal gap has narrowed. The southern state of Tamil Nadu accounts for the highest number of infections this year with 2,873 cases, followed by Maharashtra (786), Kerala (670) and Karnataka (560). Southern states consistently report higher early transmission due to warmer climates, longer mosquito breeding windows, and in some cases, more extensive diagnostic reporting systems. Taken together, the data suggest that dengue transmission is beginning earlier and spreading more persistently across the year than in previous cycles. Long-term trend and national burden Official data show that dengue cases in India have remained high in recent years, with 289,235 infections and 485 deaths recorded in 2023, the highest annual burden in recent history. In 2024, India reported 233,519 cases and 297 deaths, while 121,824 cases and 131 deaths were recorded in 2025. Public health experts say these fluctuations reflect the cyclical nature of dengue outbreaks, where large epidemic years increase population-level immunity to dominant serotypes, temporarily reducing transmission in subsequent years. However, they caution that this does not contradict the long-term expansion of dengue’s geographic and seasonal range, which continues to widen due to climate variability, urbanisation and changing mosquito ecology. Doctors say surveillance measures that usually begin around the rainy season now need to start much earlier. “We used to prepare mainly during the monsoon months,” said Dr SM Kadri, a public health consultant and former surveillance officer in Haryana.
The BriefWire