El Niño Could Trigger Dengue Surge in Colombia as Heat Accelerates Mosquito Reproduction

Colombia is bracing for a compound health crisis as the El Niño phenomenon intensifies across nine regions of the country. The extreme heat that defines this climate pattern is doing more than stress water supplies and agriculture—it is accelerating the reproduction of the Aedes aegypti mosquito, the primary vector for dengue transmission, while simultaneously creating conditions for bacterial proliferation in stored food and water. Health specialists are watching the convergence of these threats with growing concern, particularly as forecasts suggest this could develop into a super El Niño event.

The mechanism is straightforward but consequential. When temperatures climb into the 32 to 35 degree Celsius range—the optimal band for Aedes aegypti reproduction—the mosquito's life cycle compresses dramatically. At 30 degrees, the insect takes twelve days to mature from egg to adult. At 32 to 35 degrees, that timeline shrinks to seven days. The result is not simply more mosquitoes, but smaller, more aggressive ones. These younger insects are hungrier and bite more frequently, increasing their contact with human hosts and their capacity to spread dengue.

The heat does not stop at accelerating the mosquito's development. Carmen Hernandez, national director of Comprehensive Health Risk Management at Bienestar IPS, has emphasized that elevated temperatures also speed up the replication of the dengue virus inside the mosquito's body, amplifying its ability to transmit the disease to people. Simultaneously, the same heat promotes the growth of bacteria like Escherichia coli and salmonella in contaminated or poorly preserved food and water, driving up cases of gastrointestinal illness and food poisoning.

El Niño's second weapon is drought. As rainfall decreases, families across affected regions lose reliable access to piped water and resort to storing it in tanks, pools, buckets, and containers. This adaptation, born of necessity, creates an unintended consequence: when these vessels remain uncovered or go without regular cleaning, they become perfect breeding grounds for Aedes aegypti. The mosquito lays its eggs in standing water, and the warmer the water, the faster those eggs develop. A household water tank becomes a mosquito factory.

Emiro Buendia, a physician specializing in internal medicine and biomedical sciences at Serena del Mar Hospital in Cartagena, has long documented this relationship. The World Health Organization recognizes that vectors like mosquitoes are exquisitely sensitive to temperature, rainfall, and humidity—the very conditions that El Niño disrupts. When temperatures rise and precipitation falls, the ecological conditions that favor dengue transmission align almost perfectly.

The prevention measures are known but require sustained action. Hernandez recommends keeping water containers completely covered, washing storage deposits regularly, and eliminating any accumulation of stagnant water inside or around homes. These steps interrupt the mosquito's breeding cycle and reduce the standing water that bacteria need to proliferate. But in a drought, when water itself becomes scarce and precious, the discipline required to maintain these practices faces real pressure.

What makes this moment distinct is the convergence. Colombia is not facing dengue alone, nor drought alone, nor heat alone. It is facing all three simultaneously, each amplifying the others. The mosquito reproduces faster. The virus replicates faster inside it. Families store water out of desperation, creating breeding grounds. Bacteria flourish in that stored water. Nine regions are already experiencing this cascade. As El Niño continues to build, health authorities are watching to see whether the country's public health infrastructure can keep pace with a threat that is accelerating in real time.