Climate change threatens human health more than we think

It is widely believed that climate change is the greatest threat to human health. A global temperature rise of 2°C, a threshold likely to be exceeded by the end of the century, could cost as many as a billion lives. The cause of this will be extreme weather conditions, periods of extreme heat, droughts, floods, outbreaks of infectious diseases and food shortages. But the situation could be much worse in reality because current forecasts do not take into account the inevitable increase in antimicrobial resistance (AMR), that is, the resistance of pathogens to antimicrobial drugs.

Climate change could have a major impact on AMR, as there is increasing evidence that adverse weather conditions and rising temperatures facilitate the emergence and spread of drug-resistant pathogens. However, the increased risk of drug resistance is not only ignored by models measuring the impact of climate change on public health, but also by policies to combat global warming. This is a huge oversight that will hinder our ability to treat infections and protect public health.

Despite the likelihood of 11.000 species becoming extinct, a warming planet could actually improve conditions for bacteria and fungi. Higher temperatures are usually associated with increased bacterial growth and infection rates. In addition, heating can also exert selective pressure on microbes to mutate and develop resistance to antibiotics. A recent study in China found that a 1°C increase in air temperature was associated with a 14% increase in Klebsiella pneumoniae infections and a 6% increase in Pseudomonas aeruginosa infections; both bacteria are resistant to drugs.

Similarly, extreme weather events, particularly floods and droughts, will contribute to the spread of water-borne infectious diseases such as cholera and typhoid, as well as increased drug resistance. Such weather conditions usually impede access to drinking water and sanitation, making infection control and prevention difficult. In addition, the high population density in cities usually accelerates the transmission of pathogens. According to some estimates, the climate crisis could displace 2050 billion people by 1,2, and this would likely result in even greater urban overcrowding.

Antimicrobial resistance is already considered an escalating global crisis. In 2019, nearly five million deaths were linked to AMR, making drug resistance one of the world's biggest killers. The World Health Organization (WHO) lists AMR as one of the top ten threats to global health, along with climate change, and world leaders are serious about tackling the problem: a high-level meeting on AMR will be held in September on the sidelines of the UN General Assembly .

Many, however, still believe that the AMR problem is not directly related to global warming. For example, the latest Lancet Countdown report on public health and climate change does not mention AMR, drug resistance or antibiotics. Similarly, the Quadripartite Secretariat for One Health - which includes the Food and Agriculture Organization of the UN, the UN Environment Programme, the WHO and the World Organization for Animal Health - has not studied the link between global warming and AMR, and has not assessed the impact of AMR on health risks from climate change.

The international community is seriously underestimating the impact of climate change on human health and our ability to treat it. To prepare for the growing AMR crisis, we need to further strengthen infection prevention and control and, more importantly, ensure the judicious use of effective antibiotics. In addition, new antibiotics will need to be developed, which is often unattractive to pharmaceutical companies, and the right investment decisions and incentives will need to be made to ensure that existing antibiotics reach those who need them.

To that end, some organizations, like my Global Antibiotic Research and Development Partnership (GARDP), encourage new drug discovery and work to improve access to key antibiotics already on the market, especially for those living in lower-income countries. The equitable use and distribution of antibiotics will become increasingly important because AMR, like climate change, tends to hit the poorest groups of people the hardest.

These steps, however, are not enough. Global policymakers must significantly increase funding for AMR research to ensure they are prepared to respond to new forms of drug resistance caused, directly or indirectly, by global warming. This will require that AMR is included in the contingencies of climate change and, more importantly, that drug resistance and temperature rise are seen as interrelated rather than separate problems (starting with the high-level meeting on AMR in UN in September and this year's UN Conference on Climate Change (COP29) in Baku). Otherwise, the effectiveness of existing drugs will weaken at the very moment when they are most needed.

The author is the executive director of the Global Partnership for Antibiotic Research and Development (GARDP)

Copyright: Project Syndicate, 2024. (translation: NR)