14 million cases of Dengue fever were reported in 2024, more than double that recorded in 2023. This builds on a trend of increase which has been seen since the 1950s.

Dengue is a serious mosquito-borne disease. While mild cases of the disease are usually asymptomatic or result in flu-like symptoms, severe ones can lead to serious internal bleeding, caused by leaky blood vessels, resulting in shock, organ failure and death. In 2024, approximately 1 in 10,000 cases lead to death. Currently, there is no specific medication for Dengue patients, with the only option being to try and manage symptoms.

A recent study presented at the Annual Meeting of the American Society of Tropical Medicine and Hygiene at the end of 2024 suggests that climate change is responsible for 19% of worldwide Dengue cases. “We looked at data on dengue incidence and climate variation in Asia and the Americas and found that there is a clear and direct relationship between rising temperatures and rising infections,” says Dr Erin Mordecai, infectious disease ecologist at Stanford University and lead author of the study. Mordecai notes, “When the temperature gets warmer everything [mosquitos’] body does speeds up.” Not only can the virus replicate faster within the mosquito, but the insects bite more aggressively too. 

A 2020 Lancet Countdown on Health and Climate Change study agreed that climate suitability for Dengue transmission increased 9% between 1950 and 2018, amid rising temperatures.

This is worrying news for people across the world. Mordecai’s study found that annual cases could see an average 61% increase by 2050, with some areas (including parts of Peru, Bolivia, Mexico and Brazil) seeing up to 200% more cases.

Felipe Colon-Gonzalez, a climate and health expert at Wellcome Trust in the UK, predicts that “in the future, the belt of transmission is going to continue expanding northwards and upwards.” An expansion which worryingly “happens to overlap a lot with really densely populated cities” says infectious diseases researcher at Princeton, Jamie Caldwell. This could result in 2 billion people who currently live in unaffected areas being exposed to the virus by 2080, according to a 2019 climate modelling study.

Although the research gives hope that an immediate serious reduction in emissions could help to lessen the impact, it also confirms that Dengue cases will continue rise due to rising temperature, even in the most optimistic scenario.

Dengue spread is a “canary in the coal mine of climate change,” says a senior World Health Organisation official. It is a reminder that we are reaching a point of irreversible environmental damage.