Africa should bolster research into climate-sensitive diseases

Prof. Samuel Kariuki is Eastern Africa Director for the Drugs for Neglected Diseases initiative.

As a scientist working in a country affected by over 15 neglected diseases, I have witnessed with deep concern the changing disease patterns caused by climate change.

There is mounting evidence that climate change is worsening the geographical spread and incidence of infectious diseases. Scientists have found that vectors such as mosquitoes and sandflies are thriving more due to warmer temperatures, increased rainfall, and flooding. These insects transmit diseases like leishmaniasis, and dengue, which are classified as neglected diseases because they receive little attention from the global health agenda.  

The most vulnerable people are often the most affected. Climate change acts as a 'poverty multiplier', forcing millions into poverty due to loss of livelihoods, lack of access to food and clean water, but also because of increased incidence of climate-related diseases.

Take visceral leishmaniasis (VL), a neglected disease which is the largest parasitic killer after malaria; it is fatal in 95% of cases if not treated. It is transmitted by the female sandflies, which thrive in environments at approximately 25°C. As temperatures rise, more areas become suitable for sandflies to multiply. Moreover, the sandflies are more active in warm and humid environments, which could increase the frequency of bites to humans and transmission.

From 2020 to 2022, Eastern Africa, which accounts for 45% of the global VL burden, experienced the worst drought in four decades. As temperatures rose, the number of VL cases reported to the World Health Organization (WHO) also increased. In a small pastoral community, Kacheliba in West Pokot, where my organisation, the Drugs for Neglected Diseases initiative (DNDi), is conducting studies to find new treatments for VL, the number of cases has been steadily rising and clearly correlated to weather changes.

Extreme weather events such as flooding and droughts are also causing climate-related migration or displacement, which may cause people to come into contact with infected sandflies. In 2021, the Kenyan Ministry of Health reported VL cases in five additional counties, bringing the total number to 11.

It would be a mistake to regard the climate impact on VL as an isolated case. On the contrary, climate-sensitive neglected diseases are becoming more prevalent worldwide.

With the world already 1.2 degrees hotter and the World Meteorological Organization warning that global temperatures will likely soar in the next five years, the health consequences will be deadly.

In the case of dengue, the most prevalent mosquito-borne viral disease worldwide, cases recorded have increased by 85% in 50 years. Today, 50% of the world's population is already at risk of dengue. Sudan is currently experiencing the worst dengue outbreak in a decade, European countries have reported outbreaks in previously unaffected areas, Peru declared a state of emergency due to the explosion in cases, and parts of the Kenyan coast are also experiencing an upsurge.

Even the deadly sleeping sickness, which Kenya is about to eliminate as a public health problem, could reappear in the country. The WHO observed a resurgence of the disease in neighbouring Ethiopia where it recorded six cases in 2022, after more than 30 years. These cases were linked to cattle movement in search of drinking water due to the ongoing drought, which brought humans in contact with tsetse habitats.

Climate change not only threatens to undo decades of progress to control these diseases but also further widens existing health inequalities.

Medical innovation must be at the core of climate change adaptation strategies

The biggest challenge we face in Africa is the lack of effective diagnostics, drugs and vaccines to prevent, diagnose, and treat climate-sensitive neglected diseases. Biomedical innovation must therefore be a core part of the climate change adaptation strategy.

We need tools that can be easily integrated and deployed at the community level. A robust surveillance network can track disease vectors providing information to devise early warning systems that alert communities and health authorities. By strengthening healthcare infrastructure in vulnerable regions, we can respond effectively to outbreaks and guarantee access to treatment and medical supplies to everyone.

Secondly, our governments and development partners must urgently invest in new medicines and diagnostics, and in clinical research capacity building for climate-sensitive diseases.

Thirdly, to develop new treatments adapted to the needs of our communities, collaborative innovation is crucial. Endemic countries like ours should take the lead in engaging our communities, clinicians, researchers, and funders to support clinical trials.

Finally, one of the major challenges we face is that neglected diseases lack visibility. We need to make sure communities newly hit by these diseases or at future risk know what’s coming and what to do and that our governments know too. This is why all the eyes of the African neglected diseases advocates are turned to Nairobi, with the Africa Climate Summit on September 4-6. This forum will give us the opportunity to have high-level discussions and advocate for a more inclusive, sustainable, and access-oriented medical R&D agenda for climate-sensitive diseases.

The time to act is now!