The World Health Organization's (WHO) Task Team on Climate Change, Neglected Tropical Diseases (NTDs) and Malaria, in partnership with Reaching the Last Mile (RLM), has released a major scoping review published in Transactions of the Royal Society of Tropical Medicine and Hygiene. The review of 42 693 articles reveals that there is not yet sufficient understanding of the actual and potential impacts of human-induced changes to climate patterns on malaria and NTDs.
Rising temperatures and changing weather patterns are altering the spread of vector-borne diseases, with significant implications for human health and placing additional strain on systems. As the geographic range of disease vectors like mosquitoes expands, so does the risk of introducing – or reintroducing – these diseases to new, unprepared areas. The findings of this review highlight that these shifts in prevalence, incidence, range and intensity of malaria and a number of NTDs may be felt hardest in those communities already disproportionately impacted by them.
"The findings presented in this major review highlight the need for more comprehensive, collaborative, and standardized modelling, so that we can better understand and predict the effects of climate change on malaria and NTDs, both directly and indirectly," said Dr Ibrahima Socé Fall, Director of WHO's Global NTD Programme, who led the study. "This important and timely review reveals alarming trends and is a call to urgent action. Malaria transmission is likely to shift both polewards and to higher altitude, while the mosquito vector responsible for transmission of dengue and chikungunya is predicted to continue to expand its range. If we are to protect and build upon the hard-won victories of the past two decades, the time to mobilize is now."
Despite this, the paper highlights that published research has too often focused on low-disease burden countries with High Access to Quality Healthcare (using HAQI measurement). Given that the effects of climate change on malaria and NTDs will vary significantly by disease and location, exhibiting non-linear patterns and evolving over time, this focus presents what the Task Team calls a growing emergency for the communities that have been historically underserved in relation to these long-overlooked diseases.
"The climate crisis has the potential to reverse decades of progress in global health and development, said Tala Al-Ramahi, Chief Strategy Officer of Reaching the Last Mile. "Greater investment in research is urgently needed to support the development of timely and evidence-based interventions, and to allow us to anticipate and mitigate the worst consequences of climate change on human health."
With just 34% of studies reviewed (174 studies) addressing mitigation strategies and 5% (24 studies) looking at adaptation methods, this review further highlights the lack of evidence required to protect the gains made against malaria and NTDs in recent decades. Our collective progress could unravel at the hands of a climate in crisis.
"We have recently seen the consequences of extreme weather events on malaria, and they are only predicted to become more commonplace. The paper provides a clarion call for mitigation and evidence responsive adaptation to climate change," said Dr Daniel Ngamije Madandi, Director of the WHO's Global Malaria Programme. "As the impact of climate change is likely to be disproportionately borne by the poorest people, who are also disproportionately affected by malaria and NTDs, a more equitable, comprehensive and sustainable response is needed."
In order to assess the impact of climate change on malaria and NTDs, this state-of-the-art scoping review analysed peer-reviewed papers and grey literature published between January 2010 and October 2023, with investigators summarizing the identified data and analysing the distribution of studies by country.
In total, 42 693 records were retrieved, from which 1543 full-text papers were examined. Researchers correlated the number of publications with national disease burdens, the Healthcare Access and Quality Index (HAQI), and climate vulnerability scores. Of the 511 papers that met the inclusion criteria, 185 papers addressed malaria, 181 focused on dengue and chikungunya, and 53 reported outcomes on leishmaniasis. Other NTDs, however, were significantly under-represented, having not been sufficiently studied.
