Experts at the Cop30 climate summit in Belém have warned that surging cases of yellow fever and dengue in South America highlight the growing impact of the climate crisis on public health. According to Pan American Health Organization figures, there have been 356 cases of yellow fever and 152 deaths in the region so far this year, largely in the Amazon area. Apart from a spike in 2017 and 2018, this is the highest annual number of yellow fever cases on the continent since 1960.
The yellow fever outbreak follows one of Brazil’s worst years for dengue, with nearly 6.5m cases and about 5,000 deaths reported in 2024. Europe also saw a record year for dengue, with 304 cases – more than the 275 cases reported in the previous 15 years combined. Both diseases are transmitted by Aedes mosquitoes, which thrive in warm conditions and stagnant water, and scientists have determined that the climate crisis is aggravating about half of known human pathogenic diseases as mosquitoes expand their range.
Health was until recently a largely overlooked area at UN climate summits, but on Thursday the UN declared “health day” at Cop30 and promoted the Belém Health Action Plan, led by Brazil’s government and the World Health Organization. The plan aims to help countries with surveillance, best practices and capacity building. A coalition of 35 philanthropic bodies has pledged $300m in funding. Simon Stiell, the UN’s climate chief, said: “Across the world, people are living the daily reality that the climate crisis is also a public health crisis.”
Climate advocates and health experts say much more is needed to deal with the fallout. Al Gore, the former US vice-president, said recent evidence that rising heat is killing one person a minute worldwide shows governments are failing to curb the direct human harm of the climate crisis. Maria Guevara, international medical secretary of Médecins Sans Frontières, said mosquitoes and bacteria are adapting faster than humans are responding.
Health experts also cited deforestation for agriculture and housing as a factor, bringing humans closer to animals that can spread zoonotic diseases. MSF has had to respond to yellow fever outbreaks in Brazil and the Democratic Republic of Congo following severe droughts or floods, and vaccine distribution remains challenging even in countries like Brazil.
