Why climate change is giving dengue mosquitoes the upper hand

KUALA LUMPUR: For decades, Malaysians have associated dengue with the rainy season. Today, health experts say climate change is changing the rules.

Hotter temperatures and shifting weather patterns are creating ideal conditions for Aedes aegypti mosquitoes to breed, increasing the risk of dengue outbreaks while extending the period during which the insects remain active.

Dr Jemilah Mahmood, executive director of the Sunway Centre for Planetary Health, said rising temperatures accelerate the mosquito’s breeding cycle.

“When it’s hot, the incubation period for the mosquito is shorter. So the eggs hatch earlier, so you get more mosquitoes,” she told Bernama.

“It kind of speeds up, so they breed in more places and during more months of the year rather than specific times.”

The impact is already being felt: more than 33,000 dengue cases had been recorded nationwide as of the middle of June, about 21% higher than during the same period last year.

Many people assume prolonged hot weather will dry up stagnant water and reduce mosquito breeding. Unfortunately, it is not that simple.

According to Universiti Malaya epidemiologist Rafdzah Ahmad Zaki, dengue-carrying mosquitoes can pass the virus to their eggs, allowing them to survive for up to six months without water.

When rain eventually returns, the eggs hatch, potentially triggering another wave of infections.

Growing scientific evidence also points to a strong link between climate and dengue. A study published in Nature last year found that major El Niño events were associated with almost two-thirds of dengue cases across parts of Asia and the Americas during several large outbreaks.

The researchers of that study warned that continued global warming could significantly increase dengue transmission over the coming decades.

But warmer weather is only one part of the equation: health experts are also concerned about Malaysia’s high rates of childhood anaemia.

According to the National Health and Morbidity Survey 2022, nearly half of Malaysian children under five have anaemia, most commonly caused by iron deficiency.

Rafdzah said many people are unaware that anaemia can make dengue infections considerably more dangerous: “If they get infected with dengue, their symptoms will be much more severe,” she said.

Dengue suppresses platelet production and can damage blood vessel walls, increasing the risk of internal bleeding and organ failure. For people who already have fewer healthy red blood cells, recovering from the disease can be even more difficult.

Linking this to the climate, Jemilah added that prolonged exposure to extreme heat may also worsen the effects of anaemia, particularly among children and other vulnerable groups.

Taken together, mosquito-borne disease, underlying health conditions and climate change present an increasingly complex public health challenge.

This means dengue prevention can no longer rely on a single solution. Communities are still urged to eliminate stagnant water where mosquitoes breed, while working together to keep neighbourhoods clean.

As Malaysia continues to experience warmer temperatures and more unpredictable weather, the experts ultimately believe dengue is becoming more than just a seasonal concern.

Instead, they say, it is emerging as one of the many ways climate change is reshaping public health – reminding us that the fight against dengue starts long before a mosquito bite.