Impact of global warming: Dengue in winter months

Ngangom Suraj *

Impact of global warming: Dengue in winter months :: Pix - Chronicle News Service

Dengue, a viral disease traditionally associated with the scorching summer heat, is now making its presence felt in Manipur during the winter months with over 10 cases recorded in the months of January and February, 2025 . This unprecedented shift is believed to be a direct consequence of global warming, which is altering weather patterns and extending the breeding season for mosquitoes, the disease's primary vectors.

With temperatures no longer dropping as they once did, the environment remains favourable for the mosquitoes that carry the dengue virus, allowing outbreaks to occur beyond the usual summer timeframe. In fact, the state has recorded highest temperatures like never before in the last decade.

According to data issued by the Directorate of Environment and Climate Change, the year 2024 marked the highest temperature in the last decade at 42.19 degree Celsius, compared to highest temperature in 2023 recorded at 40 degree Celsius; 39.99 in 2022; 39.97 in 2021; 39.83 in 2020; 40 in 2019; 39.92 in 2018; 39.97 in 2017; 39.86 in 2016; 39.98 in 2015 and 38.93 in 2014.

Meanwhile, the recorded dengue cases also remain staggeringly high in the state with 2063 cases along with five deaths recorded in year 2024; 2548 cases in 2023; 503 with four deaths in 2022; and 203 cases in 2021.

Comparing the data, it has been observed that with rise in temperature, outbreaks of vector-borne diseases including Dengue have become intensified, as several scientific studies across the globe have also proven the same. Experts are warning that the winter spike in dengue cases could become a worrying trend if climate change continues to disrupt seasonal patterns.

The rise in mosquito activity during cooler months not only challenges public health systems but also underlines the urgent need for enhanced vector control measures and climate resilience strategies. Manipur's recent dengue cases are a stark reminder that the effects of global warming are far-reaching, impacting communities in unexpected and dangerous ways.

In an exclusive interview with The People's Chronicle, State Malaria Officer Dr Priyokumar Singh said that Dengue cases were confirmed for the first time in the entire North Eastern states at Moreh in the year 2007. After a couple of years it was detected in Churachandpur and eventually spread to other hill districts and then to the valley.

Explaining how the disease is transmitted, Dr Pri-yokumar pointed out that Dengue fever spreads primarily through the bite of infected Aedes mosquitoes, most commonly Aedes aegypti and Aedes albopictus, not directly from person to person. These mosquitoes become infected by biting a person with dengue fever and then can transmit the virus when biting a healthy person.

"The Aedes aegypti mosquito is a small usually 3-5 mm sized black mosquito with white stripes that bites people during the day and night. They live in and around houses and rest in dark areas indoors, such as under beds, behind curtains, and in closets. They lay eggs in containers that hold water, such as buckets, bowls, flowerpots, and vases and their eggs can survive for months without water," Dr Priyokumar explained.

Dr Priyokumar lamented that in India Dengue is considered as seasonal viral disease and its outbreak is recorded usually only in 6 months from June to November, however in recent years it has been detected in colder months throughout the world due to global warming.

Even though the outbreak is associated with rise in temperature and rainfall pattern, it can be prevented as the mosquito cannot fly more than 100 metres from where it hatched and the mortality rate is below 1 per cent.

Having said so, one should not take it lightly, rather involve in individual level to control it by following simple steps such as getting rid of stagnant water or adding kerosene in stagnant water, covering all stored water, wearing clothes that covers the whole body, using mosquito nets, using screens on doors and windows, and using mosquito repellents, he advised.

As the year approaches midMarch with cold days fading away and the temperature rapidly warming up, people vulnerable to the disease including infants, aged people, and people with high blood pressure, high sugar level, obese, pregnancy, frequent ulcers, asthma, kidney and liver diseases, should take special precautions, the doctor explained.

He further explained that symptoms of Dengue are high fever (40 degree Celsius), severe headache, pain behind the eyes, muscle and joints pains, nausea and vomiting, swollen glands and rashes.

However, severe symptoms may include severe abdominal pain, persistent vomiting, rapid breathing, bleeding gums or nose, restlessness, blood in vomit or stools, being very thirsty, pale and cold skin, and weakness.

Pointing out that peaking biting periods are early in the morning and in the evening before dusk, Dr Priyokumar advised that most cases of dengue fever can be treated at home with medicine however people with severe symptoms should get treatment right away.

The Directorate of Environment and Climate Change data further indicates that in the last decade the state has witnessed erratic rainfall pattern.

In 2024, the highest recorded rainfall was 329.9 mm; 156.7 mm in 2023; 308.7 mm in 2022; 214.7 mm in 2021; 294.1 mm in 2020; 214.7mm in 2020; 265.3mm in 2019; 340mm in 2018; 418.7 mm in 2017; 194.7 in 2016; 191.7 mm in 2015; and 190.2 mm in 2014.

Meanwhile, the lowest recorded temperature were 2.72 degree Celsius in 2024; 1.72 in 2023; 1.04 in 2022; 2.62 in 2021; 1.38 in 2020; 2.02 in 2019; 1.63 in 2018; 1.15 in 2017; 2 in 2016; 0.37 in 2015; and 1 degree Celsius in 2014 .