The climate crisis poses a major threat to the fight against malaria, according to the World Health Organization (WHO), with evidence suggesting extreme weather events and rising temperatures have already led to spikes in cases. Mosquitoes, the carriers of the disease, thrive in warm, damp and humid conditions, which are increasing with global heating. “The changing climate poses a substantial risk to progress against malaria, particularly in vulnerable regions,” said the WHO director general Dr Tedros Adhanom Ghebreyesus. “Sustainable and resilient malaria responses are needed now more than ever, coupled with urgent actions to slow the pace of global warming and reduce its effects.” Although data on the long-term impact of the climate crisis is scarce, the WHO’s world malaria report, published on Thursday, said rising temperatures have contributed to malaria transmission in African highland areas that were previously free of the disease. This is the first time the annual report has had an entire chapter dedicated to the climate crisis and its links to malaria. It said Pakistan saw a five-fold increase in cases after severe flooding last year – from 500,000 reported cases in 2021 to 2.6 million in 2022. Standing water became an ideal breeding ground for mosquitoes. Peter Sands, the executive director of the Global Fund to Fight Aids, Tuberculosis and Malaria, said: “I would put climate change right up there as the thing that is changing the game on malaria in ways that we can see happening, but we don’t know fully the magnitude and how it’s going to unfold.” Sands added that other factors related to the climate crisis – including displacement, the destruction of health services and increased levels of food insecurity and malnutrition – threatened progress to end the disease. “If anything, the discussion of the potential impact in the world malaria report is conservative,” he said. “We could well be seeing more dramatic consequences, partly because of the second and third-order things.” Dr Photini Sinnis, the deputy director of the malaria institute at the Johns Hopkins Bloomberg school of public health, said the climate crisis “is going to have an impact”, but that it would be hard to predict. The number of global malaria cases in 2022 remains significantly higher than before the Covid-19 pandemic, despite a slight decline in numbers, said the report. In 2022, there were 249m cases compared with 233m in 2019. The number of deaths also rose from 576,000 in 2019 to 608,000 last year. That amounts to nearly 12,000 lives each week, and pregnant women and children under the age of five are most susceptible to the disease. Most of the cases and deaths are in Africa. The report highlighted other threats to eradicating malaria, including the growing resistance to insecticides and an invasive mosquito, Anopheles stephensi, that has spread beyond its native Asian and Arabian habitats to Africa. The species has been linked to malaria outbreaks and thrives in urban settings, endures high temperatures and is resistant to many insecticides. Its spread, along with rapid urbanisation, could heighten malaria risks in African cities, said the WHO. Resistance to medicines, including artemisinin, which was critical to reducing the global burden of malaria between 2000 and 2015, is also a growing concern, according to the report. But there are signs of hope. Sinnis and Sands said there are a number of measures and initiatives in place to tackle resistance, such as the distribution of improved insecticide-treated bed nets, and the development of new insecticides and antimalarial drugs. Earlier this year, a highly effective malaria vaccine – R21/Matrix-M – was recommended for widespread use by the WHO. Doses of another vaccine, RTS,S, endorsed by the agency in 2021, arrived in Cameroon last week, one of 12 African countries expected to receive doses over the next two years. The WHO said the RTS,S vaccine had resulted in a substantial reduction in severe malaria and a 13% drop in early childhood deaths in the areas it was administered compared with areas it was not introduced. “We have, including the vaccines, quite a powerful set of tools,” said Sands. “The issue is we’re not even deploying them to their full extent. The world is not investing as much as we should to deal with malaria as it is, let alone a malaria fuelled by climate change.”