Erratic rainfall, rising heat fuel dengue surge in Delhi

Unusual weather patterns drive spike in vector-borne infections across capital.

 Rising temperatures and erratic rainfall in Delhi over the past month have led to a sharp increase in mosquito density and dengue cases, according to officials from the Municipal Corporation of Delhi (MCD). Civic authorities reported that 107 dengue cases have been recorded in the capital so far this year, with 52 cases detected in April alone. This marks the highest number of dengue cases reported during the month of April in at least the last five years.

According to MCD data, Delhi recorded 32 dengue cases in April 2025, 35 in 2024, 18 in 2023, and 20 in 2022. Officials believe that unusual weather conditions this year have created favorable conditions for mosquito breeding. April 2026 was the wettest April in 18 years, with the city receiving 30 mm of rainfall, almost double the long-period average of 16.3 mm. The previous highest April rainfall was recorded in 2008 at 38.8 mm.

Health officials explained that intermittent rainfall has prevented water from drying up completely, resulting in stagnant water collecting in drains, containers, and other open spaces. These stagnant water sources provide ideal breeding grounds for Aedes aegypti mosquitoes, the primary carriers of dengue and chikungunya. Additionally, rising temperatures above 35 degrees Celsius have accelerated mosquito activity and breeding cycles.

The mosquito density index, which measures the abundance of mosquito populations in an area, has shown a noticeable rise in several parts of Delhi. Domestic breeding checkers identified 2,443 larval breeding sites during inspections conducted over the past week alone. Between January 1 and May 3, authorities recorded 15,649 instances of mosquito breeding in homes, containers, and stagnant water sources, with nearly 15 percent of these cases detected in just the last week.

Apart from dengue, Delhi has also reported 29 malaria cases and five chikungunya cases so far this year. Although chikungunya cases remain relatively low, officials are closely monitoring the situation due to the increasing mosquito density.

To control the spread of vector-borne diseases, the MCD has intensified its enforcement measures. The civic body has issued 16,261 legal notices against mosquito-breeding violations and initiated prosecutions in 1,712 cases. It has also imposed administrative challans of ₹50,000 and above in 358 cases, recovering more than ₹1 lakh in penalties.

Officials have urged residents to maintain cleanliness, avoid water stagnation, and cooperate with anti-mosquito drives to prevent further spread of dengue and other mosquito-borne diseases.