By Christopher Lourenço, Director, Malaria & WASH, PSI
There’s no doubt: climate change will significantly impact the distribution and prevalence of malaria – with differing impacts on the parasite, the parasite-carrying anopheles mosquito, and the humans at risk of contracting the disease. While the effects will vary by country and region, we know: adaptations will be needed – across the board.
What have we learned? How are we adapting? We share, below.
Changes in and Impact on Malaria Transmission
Shifts in Geographic Distribution
Rising temperatures and altered rainfall patterns can expand the geographic range of the malaria-carrying anopheles mosquito. Plus, areas that were previously too cold for the malaria-carrying mosquitoes to survive might become suitable for their habitation.
Altered Mosquito Vector Behavior
Altered rainfall patterns can create stagnant water pools, providing more breeding sites for mosquitoes. Changes in temperature, humidity, and deforestation can also influence the lifespan and biting patterns of mosquitoes, affecting malaria transmission rates. Heavy rainfall can lead to flooding, creating temporary habitats for mosquitoes to breed. Conversely, droughts can cause water scarcity for communities, forcing people to store water in containers that may become mosquito breeding sites if not properly covered or treated.
Changes in climate can affect the seasonal patterns of malaria transmission. Warmer temperatures can shorten the incubation period of the malaria parasite, Plasmodium, in mosquitoes, potentially leading to more rapid transmission. In warmer conditions, mosquitoes mature more quickly, leading to a higher frequency of blood feeding and, subsequently, increased transmission of the disease.
Impoverished communities with limited access to healthcare and resources are at higher risk of malaria for a variety of reasons, including housing structure, residential proximity to agricultural lands with poor drainage (mosquito breeding habitats), and proximity to formal healthcare services. Climate change disproportionately affects these populations by exacerbating existing vulnerabilities, and by compounding them with climate-associated environmental risks with climate-associated health risks. For example, changes in climate patterns can affect agricultural practices and food security, forcing vulnerable populations into areas close to Anopheles breeding sites and/or further from health services. The loss of agricultural livelihoods is exacerbating food and nutritional insecurity as well. In malaria-endemic countries, rural poverty and malnutrition go hand-in-hand, rendering children, in particular, more vulnerable to the devastating consequences of malaria.
Additionally, people displaced due to climate-related events might seek shelter in regions with higher malaria transmission, increasing the overall at-risk population and strain on health systems. Displacement and migration due to climate-related factors can also lead to the mixing of populations, potentially introducing the disease to new areas.
Climate change can also affect human behavior. For instance, during heatwaves, people may spend more time outdoors and be less likely to use bed nets or wear protective clothing, increasing their exposure to mosquito bites.
How We’re Adapting
Surveillance and Early Warning Systems
Improved epidemiological and entomological surveillance can help monitor changes in malaria patterns. We have two examples of this, through USAID support.
- In Zanzibar, the team supports the Zanzibar Malaria Elimination Program to track the proportion of local to imported malaria cases, and therefore an important threshold to inform when scaling up response activities is needed; this was identified as a key metric during the outbreak in 2023 after a longer-than-usual rainy season increased malaria transmission.
- In Angola, we’re establishing multi-sectoral vector surveillance for Anopheles stephensi and will bring together the Ministry of Transportation and the Ministry of Health, revitalizing this collaboration at points of entry and providing a critical opportunity to build resiliency in Angola for this invasive mosquito.
Early warning systems, based on climate data and disease modeling, can provide advance notice of changing malaria transmission risks, enabling targeted interventions and building resilient systems. Under BMGF, DFAT, and PMI investments, we supported the governments in Southeast Asia to improve malaria surveillance systems and capacities through private sector inclusion, improved dashboards and alert systems, case investigation and response protocols, and outbreak response capacity. Developing and enhancing systems can help communities prepare for increased malaria risk, as exemplified by our work in strengthening Emergency Operation Centers (EOCs) at the central and subnational levels in Lao PDR.
Improved Healthcare Infrastructure
Health system strengthening is at the heart of many of our projects, as accessible healthcare can reduce malaria-related morbidity and mortality. Here’s how:
- In Cameroon, 1,400 children ages <2 were received at the health facility after Community Health Workers provided referrals for delayed routine child health and malaria preventive services through the Unitaid-funded Plus Project between January and June 2023.
In Tanzania, with PMI support, the DHIBITI MALARIA team is reinforcing facility-based malaria service delivery through supportive supervision and mentorship for diagnostic and treatment services, and coupling these supervision activities with client feedback surveys to regularly incorporate community needs into supervision and service delivery quality improvement initiatives.
Continued research is vital to understand the complex interactions between climate change, mosquitoes, parasites, and human populations. Research to enhance vector control approaches in the setting of considering changing mosquito behaviors, such as the continued development of dual active ingredient insecticide-treated bed nets, and monitoring of their effectiveness, remains crucial. We have supported these endeavors through initiatives like the Unitaid-funded New Nets Project, and will continue to advocate for continued research in new vector control.
Climate change will affect the geographical range, intensity, and seasonality of vector-borne diseases such as malaria, in ways that cannot be precisely predicted, highlighting the need for evidence-based and flexible responses.
Photo caption: Community mobilizers-distributors pictured during a 2019 seasonal malaria chemoprevention campaign in Cameroon.