A looming global health crisis – The Mail & Guardian

several regions of South Africa have been battered by floods over recent years, resulting in thousands of people being injured and displaced and several fatalities.
(Photo by RAJESH JANTILAL / AFP)

Climate change risks triggering epidemics of emerging and re-emerging diseases across the world with “disastrous consequences”.

This is the warning sounded by a team of scientists in an invited commentary on infectious diseases in a warming world, published in the latest issue of the South African Journal of Science.

“As the world begins to recover from the Covid-19 pandemic, it is crucial to recognise that another looming crisis demands our immediate attention,” the authors from the Centre for Epidemic Response and Innovation at the School of Data Science and Computational Thinking at Stellenbosch University said.

“Human-induced climate change is frequently discussed in terms of its impact in the mid to long-term future with gradual long-term shifts in global climate patterns.”

Current events, however, show the devastating consequences of climate change from extreme weather events. 

The researchers cited, as a recent example, the compounding effects of heatwaves and long-term drought driving wildfires in the Brazilian Pantanal, damaging up to 9% of the world’s largest wetland. Closer to home, several regions of South Africa have been battered by floods over recent years, resulting in thousands of people being injured and displaced and several fatalities. 

“The physical damage caused by these climate events burdens healthcare systems but, regrettably, amid these challenges, there is another impending threat to our health that requires urgent attention — the intricate interaction between climate change and infectious diseases,” the authors said.

New era of outbreaks

Humanity, they warned, is facing a new era of global health with outbreaks of endemic, emerging and re-emerging pathogens set off by climate and global change, and “swiftly spread by global connectivity”. A recent review revealed that climate change has the potential to aggravate almost 60% of known human pathogens. 

Warming effects, changes in precipitation levels and floods are the most prominent climate hazards that stimulate vector-borne, waterborne and airborne diseases, they noted.

West Nile virus, a vector-borne virus of African origin spread by mosquitoes, has “taken on an almost global distribution” within the last two decades, facilitated by climate effects, with devastating outbreaks in Europe and the US.

The incidence of diarrhoea, particularly among children in low and middle-income countries of Africa, South America and South Asia, increases during floods, and floods preceded by drought, as these events reduce the quality of drinking water sources and contaminate them with pathogenic agents.

Changes in temperature and rainfall have also been shown to affect human social behaviour, as people favour indoor activities over outdoor activities during unfavourable weather conditions “and, depending on indoor ventilation rates, this may facilitate the transmission of airborne diseases like Covid-19”.

The “slow but consistent increase” in global temperatures is enabling climate-sensitive disease vectors, such as mosquitoes and ticks, to expand their geographical ranges into new territories and reproduce at a faster rate, increasing their ability to transmit diseases.

Altered rainfall patterns can create breeding grounds for mosquitoes, which escalates the incidence of vector-borne diseases, the scientists said, noting that such increases in these diseases have been noticed around the world. 

“For example, in 2023, there was a large outbreak of chikungunya virus in South America with over 120 000 confirmed cases and 51 deaths. Of those deaths, 46 occurred in Paraguay, causing substantial health disruptions as the virus spread to all corners of the country.” 

This was the largest outbreak of chikungunya virus ever recorded in Paraguay and coincided with the highest average reported temperatures in the country’s history.

In 2023, there was an extremely high global risk of contracting dengue virus, with an estimated 40% of the population at risk, partly attributed to the El Niño phenomenon and humanitarian crises, they said. “At this time, 15 countries within the World Health Organisation’s African region had reported cases of dengue with the number of infections in the region nine-fold higher than in 2019.”

Extreme climate events

In the face of climate change and land-use change, to survive, many animal species will need to move their home ranges along with the environment as it changes. “Such local and large-scale movements of animals will cause new species to interact with one another, potentially stimulating novel pathogen-sharing events and disease emergence in wildlife. 

“These pathogen-sharing events have the potential to be globally devastating, just as the SARS-CoV virus jumped from bats into civets, which enabled infections of humans and caused a mini-pandemic in 2002 to 2003.”

Extreme climate events are sudden and severe weather conditions, such as floods, cyclones and wildfires, which devastate communities, agriculture and natural ecosystems.

These events are “increasingly causing or amplifying infectious diseases in a warming world”, causing disease outbreaks by contaminating drinking water; displacing people and animals from their homes; disrupting social services; destroying crops and creating conditions of malnourishment “such that affected communities are less capable of naturally fighting off disease”. 

“These disasters often unfold quickly, catching countries off guard with limited time to prepare treatment facilities or interrupt disease transmission. Arguably, one of the most devastating infectious diseases triggered by extreme climate events is cholera,” the researchers said.

“According to the [World Health Organisation], as of mid-2021, we are in the midst of an acute upsurge of the seventh global cholera pandemic. This pandemic has been characterised by multiple large outbreaks, spread of the bacteria to previously cholera-free areas and alarmingly high mortality rates.” 

In 2022, Pakistan experienced extreme flooding, resulting in hundreds of thousands of infections. The strain responsible for this outbreak was also associated with the deadliest cholera epidemic in Malawi’s history, with over 57 000 confirmed cases and 1 733 deaths during the 2022-23 outbreak.

Act now

Long-term droughts are causing crop failures and raising issues of food insecurity, while desertification fosters conflict over water access. “Disrupted access to food and water prompts both people and animals to migrate in search of these basic resources as well as new economic opportunities,” they said.

“Regional and international movement of people may stimulate outbreaks by the introduction of pathogens into non-endemic areas to naive populations, through susceptible migrants being exposed to new pathogens or from overcrowding in informal settlements.” 

There have been 12 recorded outbreaks of acute viral hepatitis in forcibly displaced peoples in sub-Saharan Africa since 2010, with at least 30 000 cases and over 600 deaths. “These outbreaks have been attributed to poor sanitation and overcrowding conditions, which are a consequence of climate-induced migration and displacement of people.”

While countries in the Global South contribute less than 10% of greenhouse gas emissions, they are more at risk of climate-related health threats and have less adaptive capacity to respond to these threats, the experts said. “As such, low and middle-income countries are highly vulnerable to climate-induced hazards.” 

“In response to the climate-health crisis in the Global South, the Climate Amplified Diseases and Epidemics (Climade) consortium has banded together leading scientists working to close knowledge gaps, improve disease surveillance tools and develop disease transmission interventions to decrease the impact of climate-amplified diseases.” 

Climade is urging governments and health organisations to report outbreaks timeously and transparently, as this is crucial for global preparedness and outbreak response efforts. Governments, academic institutions and health organisations must also expand and strengthen disease and genomic surveillance capacity. 

The consortium wants the development of adequate healthcare, infrastructure and disaster preparedness systems for vulnerable populations to be prioritised globally while academic institutions and private sector industries should promote climate resilience within healthcare systems.

“Climade calls on governments, private sector industries and health organisations to commit sustainable funding for research, capacity-building and community engagement in the fight against climate change related infectious diseases. 

“With the world already grappling with climate-induced disease outbreaks, we need immediate and concerted action to address the complex challenges posed by the intersection of climate and health.” 

The authors said that building global capacity, improving surveillance and developing climate-resilient healthcare systems are critical steps in safeguarding communities from further harm. “The window to act is narrowing; we need to work collectively to mitigate potential public health losses and build a more resilient, equitable future for all.”