How climate change threatens to increase malaria transmission

Un niño en Ghana es inoculado con la primera vacuna contra la malaria.


In 2020, 241 million cases of malaria or malaria were registered in the world, according to the most recent global report on the disease from the World Health Organization (WHO). The number of deaths that same year was estimated at 627,000.

April 25 is World Malaria Day, when the WHO reiterates its call to fight collectively for a world free of the disease.

While there have been advances such as the first malaria vaccine, which was approved by the WHO last year, climate change and rising temperatures could see this deadly disease spread to areas where it was never present.

deadly spread

“Warmer temperatures increase the ability of mosquitoes to carry the parasite that causes malaria,” says Dr Isabel Fletcher, data technology manager at the Wellcome Trust, a London-based biomedical research charity.

Climate change will make more areas of the world suitable for malaria-carrying mosquitoes. As the world gets warmer, malaria is expected to expand into new mountainous areas that may currently be too cold for transmission,” he warns.

According to the United Nations Intergovernmental Panel on Climate Change (IPCC), even if all government plans announced by the end of 2020 were implemented, without more drastic cuts in greenhouse gas emissions the world will warm 3.2°C by the end of the century.

The global goal is to keep the rise in temperatures to 1.5°C or less by reducing carbon emissions.

A woman sitting on her bed around which she placed a mosquito net

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A woman tries to protect herself against malaria in Anzoátegui State in Venezuela.

In addition to rising temperatures, the researchers warn that rain and humidity, and even dry conditions, can also lead to faster growth of malaria-carrying mosquitoes where the disease was previously absent.

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“Studies have shown in the Caribbean countries and in Brazil that when there is a dry period, people store more water. That creates a good habitat for mosquitoes. That is why, for example, during droughts it is possible that dengue transmission increases,” says Fletcher.

And there is a fear that the same thing will happen with malaria.

Climate change could also reduce malaria transmission in some areas where conditions are already optimal, which is why Fletcher believes gaining a better understanding of the impact of temperature changes will be key in the continued fight against the disease.

“By creating risk projections for the future, we can identify the populations that are most at risk and, based on that information, target interventions,” he says.

Boy with malaria lying with his head on his mother's lapBoy with malaria lying with his head on his mother's lap

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The first common symptoms (fever, headache, chills and vomiting) usually appear 10 to 15 days after the infection has occurred. If left untreated, P. falciparum malaria can lead to serious illness and death within 24 hours, according to the WHO.

What are the symptoms of malaria?

Malaria is a serious infection transmitted by mosquitoes, which can cause death if not diagnosed and treated quickly. Symptoms include:

• high temperature, sweats and chills

• headaches and feeling confused

• feeling very tired and sleepy (especially in children)

• upset stomach, tummy ache, and diarrhea

• loss of appetite

• muscle pains

• yellow skin and eyes

Source: NHS (UK Health Service)


Vaccine Success

At the same time that climate change threatens to make the fight against malaria more difficult, there have been advances against the disease.

The WHO recently announced that more than a million children in Ghana, Kenya and Malawi have already received one or more doses of the first malaria vaccinethanks to a pilot program coordinated by that organization.

The first tests of the new vaccine, authorized by the Malawi government in April 2019, showed that the RTS,S/AS01 (RTS,S) vaccine is safe and feasible to administer, and that substantially reduces mortality from severe malaria.

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It was the early stages of this program that led the WHO to approve its widespread use in sub-Saharan Africa and other regions with moderate to high malaria transmission.

Workers in a laboratoryWorkers in a laboratory

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The RTS,S vaccine is the first malaria vaccine approved by WHO for use in children.

What is the WHO strategy to prevent malaria?

The WHO has established a roadmap to combat the disease. The goals of the organization include:

• reduce the incidence of malaria cases by at least 90% by 2030

• reduce mortality rates by at least 90% by 2030

• eliminate malaria in at least 35 countries by 2030

• prevent a resurgence of malaria in all malaria-free countries.

Source: WHO


The WHO estimates that the vaccine could save the lives of between 40,000 and 80,000 African children each year.

“We were able to observe the impact of the vaccine after two years. We saw that the vaccine is very safe and well tolerated,” says Dr Mary Hamel, who leads the WHO malaria vaccine implementation programme.

“During those first two years of vaccine administration there was a considerable impact with a one-third reduction in hospital admissions for life-threatening severe malaria“.

In addition to RTS,S, there are also other candidate malaria vaccines. R21/Matrix-M is one of them and is in the early stages of clinical trials.

Pharmaceutical giant BioNTech is also seeking to develop a malaria vaccine using the same cutting-edge mRNA or messenger RNA technology first used in a COVID-19 vaccine.

How does the vaccine work? Are there enough supplies?

More than a million children in three pilot countries have received one or more doses of the first malaria vaccine, according to the WHO.

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In malaria, a parasite invades and destroys human blood cells in order to reproduce and is transmitted by the bite of blood-sucking mosquitoes.

Little girlLittle girl

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More than a million children in three pilot countries in Africa have already received one or more doses of the RTS,S vaccine, according to the WHO.

The RTS,S vaccine acts against the deadliest and most common parasite in Africa: Plasmodium falciparum.

When a victim is bitten by a mosquito, the parasite enters the bloodstream, infecting liver cells.

The vaccine is designed to prevent the parasite from infecting the liverwhere it can mature, multiply, reenter the bloodstream, and infect red blood cells, causing symptoms of the disease.

The vaccine needs four doses to be effectivethe first three one month apart at the ages of five, six and seven months, and the final booster at 18 months.

MosquitoMosquito

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More than 240 million cases of malaria were recorded in 2020 and the disease caused 627,000 deaths that year, according to the WHO.

Health experts recommend that the vaccine be used in combination with other strategies to prevent infection and reduce disease transmission.

The WHO expects the demand for vaccines to exceed 80 million doses a year, particularly in sub-Saharan Africa.

This high demand poses great challenges.

Supply will quickly be outstripped by demandsince the manufacturer is in the process of increasing the production of vaccines”, explains Hamel.

Currently there is only one manufacturer, the pharmaceutical company GlaxoSmithKline (GSK).

“The plan is to scale GSK’s production up to 15 million doses per year,” adds Hamel.

“We really have to muster the necessary commitment and political will, and make sure that there is enough vaccine to reach children at risk of severe malaria.”


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