Climate change and an epidemic of mosquito-carried diseases

The impacts of the climate crisis, from devastating wildfires across Canada, Greece and Hawaii, to flooding and landslides in India and Libya, are clear to see. But there are also unseen effects of climate change that are increasingly posing risks to our health. 

Rising global temperatures, changing rainfall patterns and other extreme weather conditions bring to the fore climate-related health concerns that demand new solutions. The threats of vector-borne diseases, which are transmitted to humans by other organisms like mosquitoes or ticks, are being exacerbated by climate change. 

To put this in perspective, by 2080, climate change and increasingly urbanised societies could cause six billion people worldwide to be at risk of dengue fever, which is spread by mosquitoes. But climate change is also impacting the spread of dengue now. In 2022, Brazil recorded 2.3 million cases of dengue and almost 1,000 deaths from the disease, during the largest dengue outbreak in the country on record.

Over the next century, vector-borne diseases are projected to increase across more temperate parts of the world as they become warmer and wetter. The locations at risk of being affected include northeastern USA, the highlands of Central America, the Andean region of South America, eastern South America, the horn of Africa, South Africa, Madagascar, eastern Australia, and parts of Indonesia and East Asia, and even some parts of Europe. While the types of mosquitoes that spread these diseases are currently less common in these locations, the population at risk of these diseases will increase by as much as 4.7 billion by 2070.

However, these diseases could decrease in frequency in areas where disease-carrying mosquitoes are currently more common. These include places like the northern half of South America, sub-Saharan Africa, the Indian subcontinent, southeast Asia, and northern Australia.

Under all potential climate models – from worst-case to best-case scenarios – the picture over the coming decades will change. People who have not yet come across disease-carrying mosquitoes might soon need to think about how to protect themselves. This is a growing problem of global concern, which does not differentiate between more- and less-developed countries.

Currently, there are two vaccines approved to protect against dengue fever, one in the US and one in Europe, and several more in development. However, there are currently no approved therapeutic drugs for dengue. 

Mosquito control has historically been the main tool to limit the spread of dengue, including fogging streets and homes with insecticides, using mosquito traps, repellents, nets and introducing predators which eat the larvae. However, with the climate-driven expansion of mosquitoes' range, emerging resistance to insecticides, and rapid urbanisation, new tools are needed to control the outbreaks of mosquito-borne diseases, like dengue and other arboviruses.

To respond to the rising threat of vector-borne diseases exacerbated by the impacts of climate change, new technologies are being developed to respond to the challenge. 

Artificial intelligence (AI) could be a solution used to detect and prevent vector-borne epidemics. AI was used to detect the first signs of Covid-19, and could be used to monitor, predict and prevent the spread of diseases like dengue fever and malaria. 

"Vector-borne disease will be impacted or affected by the climate, and we have the data that shows in dengue, for example, it's affected by temperature, the rainfall and the wind speed," says Imran Bambudi, the director of disease prevention and control in the Indonesian Ministry of Health.

Bambudi is using artificial intelligence to predict outbreaks of dengue fever in Jakarta, using existing analyses of the region's weather changes. "We've found that mosquitoes will bite a human every five days if the temperature is below 20C. But, the number will increase by three times if the temperature goes up to 30C," Bambudi says. "AI can help us to analyse this data and these factors, to predict whether the region will experience more malaria and dengue fever outbreaks."

Case fatality rates are currently lower in 2023 than they were in 2022, which Bambudi says is a positive step. "The number of cases in Indonesia is still high, but the fatality rate being lower means that the awareness we are raising and the information we're able to give based on these predictions is helping."

Providing enough evidence and tracing to track the changes occurring in the diseases is forcing the research community to assess how many patients have presented with dengue and the level to which it has become a public health concern, according to Oyibo. 

While solutions are a high priority, the need to adapt to climate change impacts is also of utmost importance. "The organisms and diseases we're dealing with are subject to change, and that change could be rapid. So awareness is fundamental in order to drive progress in understanding the issue and in succession, providing a strategic solution. That's the key to putting a stop to this."

That vector-borne diseases will continue to spread and change in time with the changes to the climate means experts like Oyibo, Bambudi and de Castro face a continuously moving target. But, mapping, AI, biobanks and new advances in treatments and prevention like Wolbachia offer some tools with which the healthcare sector can keep pace.