Climate’s clear connect: Africa is proof that extreme weather triggers and exacerbates disease; here’s how

Whether its is zoonoses or water-borne diseases, climate change has a clear role to play in their spread on the continent


Eliza Tangwe, 18, takes a dose of oral cholera vaccine at a health centre in Blantyre, Malawi, in November 2022. The country is in the middle of its worst outbreak of the waterborne disease (Photograph: Reuters / Eldson Chagara)On February 13 this year, President Lazarus Chakwera of Malawi launched a national campaign that carried the gravity of a battle cry: “Tithetse kolera (End Cholera)”.

He spoke from Mgona, one of the cholera hotspots in capital city Lilongwe, as patients were ferried to health centres.

He declared that the landlocked southeastern African nation’s immediate challenge was to reduce the fatality rate of the current cholera outbreak from 3.2 per cent to the global average of about 1 per cent by the end of the month.

The acute diarrhoeal infection, caused by consuming food or water contaminated with bacterium Vibrio cholerae, has been endemic to Malawi since 1998, when the country reported its first major outbreak of the disease.

Cases remained confined to the flood-prone southern districts, occurring usually during the rainy season of November-May.

But the current outbreak is unprecedentedly protracted — it started in the southern district of Machinga in March 2022 and by February 2023, had spread to all the 29 districts of the country, infecting 36,940 people and killing more than 1,200, as per a February 9, 2023 update by the World Health Organization (WHO).

“This is the deadliest outbreak of cholera in the country’s history,” says WHO in a statement.

What makes the outbreak a matter of concern is that the current surge in cases comes after the country had managed to bring down cholera cases to just two in 2021.

Analysts see a clear link between the uptick of cholera cases and the unprecedented monsoons, major floods and a succession of cyclones that have battered the country in the past one year.

The outbreak started after three tropical storms hit southern Malawi one after the other. In January 2022, the once-in-half-a-century storm Ana hit the region, followed by tropical storm Dumako in February and cyclone Gombe in March.

The region was flooded and over a million people displaced, who took shelter in cramped tents in swampy areas without access to safe water and sanitation. This aggravated the situation.

Till August 2022, cholera was limited to the flood-affected districts, but spread to northern and central districts during the dry season. “This upsurge in the number of cases is being reported during the country’s dry season when normally there is low or no transmission of cholera in Malawi,” says a December 7, 2022 report by WHO.

Malawi’s secretary for health Charles Mwansambo says this unusual spread of cholera has been induced by climate change impacts. “Last year, we had tropical cyclones and floods that destroyed most of the water and sanitation facilities in the southern region, and this was the start of the current problem of cholera,” Mwansambo was quoted as saying by Swiss non-profit Health Policy Watch.

What aided in the transmission of the infection across the country, even during the dry season, are the usual factors like mass displacement due to conflicts, lack of basic water and sanitation facilities in most parts of the country, a highly mobile fishing community in the north and prevailing food crisis (estimates show 20 per cent of the country’s population could be experiencing “crisis” levels of food insecurity).

Kampala City Council Authority  officials at an Ebola awareness  event in the Ugandan capital on February 1, 2023. The country has reported 32 outbreaks of Ebola since 2000, the latest being in 2022, which was termed the worst in two decades  (Photograph: Ollivier Girard / European Union)

Speaking to Down To Earth (DTE), Ted Bandawe, director of the Mzuzu Central Hospital in the northern town of Mzuzu, says climate change is no doubt a risk factor for cholera due to increased rainfall and warmer temperatures.

“High temperatures can cause increased levels of pathogen growth and spread, while increased rainfall can lead to flooding, which can compromise water sources and lead to more cases of cholera,” Bandawe says.

But such outbreaks are becoming widespread and deadlier due to increased frequency, intensity and duration of natural disasters. “These lead to displacement of large populations and overcrowding in camps, without sufficient supplies of clean water and food, leading to a perfect environment for disease outbreaks like cholera,” says Bandawe, adding that climate-linked health emergencies are on the rise in Malawi.

Continental scourge

Scientists say infectious diseases like cholera could in fact be a constant hazard for the entire continent of Africa, which is particularly vulnerable to extreme weather events.

All forecasts, including that of the Intergovernmental Panel on Climate Change (IPCC), suggest that Africa is warming faster than the rest of the world on average. It will be warmer by 3.6°C by the time the world warms up by 2°C.

Rainfall will decrease in northern and southern Africa, and increase in the Sahel region. “Scientific evidence shows a significant link between climate change and the rise in disease outbreaks across the continent, especially vector-borne and water-borne ailments,” Kenya-based Githinji Gitahi, group CEO of global health non-profit Amref Health Africa, tells DTE.

In April 2022, WHO in a comprehensive and definitive assessment said that climate-related health emergencies are on the rise in Africa. Of the 2,121 public health events in the continent in the two preceding decades, 56 per cent were climate-related.

Waterborne diseases like cholera accounted for 40 per cent of the climate-related health emergencies; vector-borne diseases, notably yellow fever, accounted for 28 per cent of the climate-related health emergencies, while zoonotic diseases, specifically Congo-Crimean haemorrhagic fever, were the third most prevalent.

In August that year, Nature published a study which said that 58 per cent (218 of 375) infectious diseases faced by humanity have been at some point aggravated by climatic hazards (see ‘Aggravated by climate’,). These include dengue, chikungunya, West Nile virus, Zika and malaria that are regularly reported by African countries.

More than half of known human pathogenic diseases can be aggravated by climate change

To understand the growing prevalence of infectious diseases in a warming world, DTE analysed WHO’s weekly bulletin of outbreaks and other emergencies published between March 2017 and February 2023.

The findings show a significant rise in disease outbreaks during the five years. In the second week of February 2023, African countries reported 125 disease outbreaks.

This is more than 2.8 times the outbreaks reported in the same period in 2018, when WHO registered 44 outbreaks in the continent. The increase has been more than six times when compared with the first week of March 2017, when WHO registered 21 disease outbreaks.

Climate change-linked outbreaks also increased — from almost four in a week in 2017 to about 11 a week in 2023 (see ‘Stark increase’,).

Consider malaria, a mosquito-borne disease that has been afflicting the continent with unparalleled severity. Africa has the world’s highest burden of the disease.

According to WHO’s “World Malaria Report 2022”, some 96 per cent or 238 million of all cases and 98 per cent or 603,877 of all deaths due to the disease occurred in Africa in 2021. Between 2017 and 2021, cases of malaria have risen by 17 per cent across the continent.

Studies show this spread is due to climate change-induced favourable conditions. Malaria epidemics often occur after periods of unusually heavy rainfall.

In addition, warming in the east African highlands is allowing malaria-causing Anopheles mosquitoes to survive in higher altitudes. The mosquito expanded its range on the African continent, reaching higher elevations and moving southwards from the equator, aided by climate change in the last century, says a study published in the journal Biology Letters in February 2023.

The researchers used datasets compiled by medical entomologists to track the observed range limits of African malaria mosquito vectors from 1898 to 2016.

The researchers note that the changes in the range of the malarial vectors “would be consistent with the local velocity of recent climate change and might help explain the incursion of malaria transmission into new areas over the past few decades”.

The study says that, “If confirmed, the rapid expansion of Anopheles ranges—on average, over 500 km southward and 700 m uphill during the period of observation—would rank among the more consequential climate change impacts on African biodiversity that have been observed to date.”

Climate change linked diseases and crises have seen a clear rise across Africa in the past five years

According to the researchers, malaria will spread into highland east Africa and expand at its southern limits (south of the Congo, towards the Cape), but the transmission will likely decrease as west and central Africa become prohibitively warm.

As per an estimate by the Emerging Pathogens Institute, University of Florida, US, in the worst-case regional scenario of climate change, an additional 75.9 million people will be at risk from 10-12 months’ exposure to malaria in eastern and southern Africa by 2080, with the greatest population at risk in Eastern Africa.

Similarly, there has been a surge in cases of measles, a disease that can cause child deaths but is preventable by vaccine. Between January and March 2022, sub-Saharan Africa has recorded a 400 per cent increase in measles cases.

In March, South Africa has declared an outbreak of the disease. Studies say that the virulence and survival of measles virus in air is mainly influenced by temperature and relative humidity. A study published in Science News in August 2020 states that the measles cases were higher during the dry season.

Zoonoses also on the rise

Another worrying trend because of climatic factors is the growing risk of zoonotic pathogens such as the novel coronavirus (SARS-CoV-2) that transmit from animals or birds and cause severe disease outbreaks in humans. A July 14, 2022 analysis by WHO shows that Africa has seen a 63 per cent rise in outbreaks of zoonotic diseases in 2012-22 compared to 2001-11.

Uganda, for instance, has reported since 2000 as many as 32 outbreaks of Ebola, a viral haemorrhagic fever that commonly affects non-human primates like monkeys and gorillas.

Of the 32 outbreaks, 19 were reported in the last decade, compared to 13 in the preceding one, as per a November 2022 WHO press release. The latest outbreak in 2022, which was declared over in January this year, has been termed the worst in two decades.

The virus had spread from the epicentre Mubende district to seven others by 2022. Misaki Wayengera, a medical researcher and chairperson of Uganda’s Scientific Advisory Committee at the Ministry of Health, tells DTE, “Factors such as increased human activity in natural habitats, population dynamics, and climate change are all involved. Increased encroachment on natural habitats, mining, and logging create an interface between humans and animals, leading to a spillover event or species jump.”

For instance, following frequent droughts, often cited as a symptom of climate change, bats and other animals that carry the virus move to places that happen to be human habitats.

A woman at a camp in Chikwawa town of Malawi in September 2022. The country was hit by cyclone Ana 
in January  2022, forcing more than a million people to live in unsanitary conditions

Low on immunity

The burden of infectious diseases in Africa is only going to rise in a warming world. A combination of extreme weather events and resultant crises will force populations to flee homes, damage the crumbling water and sanitation infrastructure and exacerbate the prevailing food crisis. At the same time, climate change impacts are making people vulnerable to infectious diseases.

In 2000-09, every tenth Kenyan has been hit by a natural disaster, says “Climate risk management for Malaria Control in Kenya-The case of the western Highlands”, a report released in 2013 by the International Institute for Sustainable Development.

The impacts of climate change on health across Kenya, where over 80 per cent of the land is arid or semi-arid, are primarily in terms of direct mortality and injury from natural hazards and indirectly mediated through the environment, according to “Climate Change Impacts On Health: Kenya Assessment” a 2021 assessment report by International Federation of Red Cross and Red Crescent Societies.

“About 970,000 children aged 6-59 months and 142,000 pregnant or lactating mothers in Kenya will likely suffer from acute malnutrition over the course of 2023 and are in need of treatment. This state of malnutrition among these vulnerable populations has compromised their immunity and increased their risk of exposure to disease,” says Mohamed El Montassir, the Kenya Country Director of global non-profit International Rescue Committee.

The drought situation in Kenya is getting worse, with over 5.3 million people now facing famine and starvation—an extra 1.2 million from December’s figures, according to monthly data from Kenya’s National Drought Management Authority. The authority said in January that the number of affected people by December 2022 was 4.35 million, with livelihoods worth $1.5 billion lost last year alone.

In fact, three countries in the Horn of Africa—Kenya, Ethiopia and Somalia—have entered the sixth consecutive rainy season with no rain, the United Nations High Commissioner for Refugees said in a statement on February 28. These countries have been experiencing an ongoing drought since late 2020.

Millions of people have moved to relief shelters, while those left in villages scavenge for food and water. The trail of diseases is getting denser day by day. According to WHO, climate emergencies accounted for 72 per cent of all recorded public health events in 2021.

This is a significant increase compared to 58 per cent in 2011, according to Mary Stephen, a public health expert at WHO. While Africa has progressed significantly on its disease-control programmes, leading to a rise in overall life expectancy, the climate change-induced disease outbreaks would not just undo it but also add to the huge disease burden.

“The foundation of good health is in jeopardy, with increasingly severe climatic events. Although the continent contributes the least to global warming, it bears the full consequences,” says Matshidiso Moeti, WHO Regional Director for Africa.

This was first published in the 16-31 March, 2023 print edition of Down To Earth

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