Global climate change could create more opportunities for rise and spread of new cholera strains
Scanning electron micrograph image of cholera bacteria.
New research suggests that an El Niño event may have aided the establishment and spread of a novel cholera strain during an early 20th-century pandemic, supporting the idea that climate anomalies could create opportunities for the emergence of new cholera strains. Xavier Rodo of Instituto de Salud Global de Barcelona, Spain, and colleagues present these findings in the open-access journal PLOS Neglected Tropical Diseases.
Since 1961, more than 1 million people worldwide have died in an ongoing cholera pandemic, the seventh cholera pandemic to have occurred since 1817. The drivers of past cholera pandemics have been unclear, but one hypothesis holds that anomalous climate conditions may act synergistically with genetic changes of Vibrio cholerae—the bacterium that causes the disease—to facilitate the spread and dominance of new strains.
To help clarify potential links between climate and cholera, Rodo and colleagues applied a variety of statistical and computational tools to historical records of climate conditions and cholera deaths in various regions of former British India during the sixth cholera pandemic, which lasted from 1899 to 1923. They also compared past conditions with climate and cholera data for the ongoing pandemic.
This analysis revealed that anomalous patterns of cholera deaths from 1904 to 1907 occurred alongside out-of-the-ordinary seasonal temperatures and rainfall levels associated with an El Niño event; the timing of these occurrences correlates with the establishment of a new invasive strain during the sixth pandemic. In addition, these historical climate conditions show similarities to strong El Niño events that have been associated with cholera strain changes during the ongoing pandemic.
These findings support the possibility that anomalous climate events could help facilitate the establishment and spread of new cholera strains.
The researchers then explored future possibilities for climate-facilitated emergence of new cholera strains using standard climate prediction models. They found that climate change-driven increases in climate variability and extremes could boost the chances of emergence of novel strains through the end of the current century.
Meanwhile, to deepen understanding of this deadly disease, the scientists call for further research focused on the interplay of cholera evolution and climate anomalies.
Dr Rodó and co-author Dr Mercedes Pascual summarise: “Variation in climate conditions or the evolutionary change of a pathogen can be important drivers of major epidemics and pandemics. But these two drivers are typically considered separately in studies seeking to explain the emergence of unusually large outbreaks…here, we present indirect evidence that the two can act together to synergistically underlie the establishment and widespread transmission of a new strain.”
South Africa’s sewage crisis has dire consequences for public health, waterways, and ecosystems. Outdated and poorly maintained wastewater infrastructure due to insufficient investment is one factor that results in poor waste management. The strain of rapid urbanisation with inadequate sanitation facilities in informal settlements and the exacerbating impact of climate change through increased rainfall events are also factors that contribute to poor waste management. Despite these challenges, there is room for optimism. Collaborative efforts between government and the private sector have the potential to address this dire situation, bringing forward practical, affordable solutions that hold the promise of a cleaner, healthier future for all communities.
A public health crisis: deadly waterborne diseases
South Africa’s persistent sewage crisis recently sparked a new cholera outbreak, primarily stemming from dysfunctional municipal sewage systems. Over 90% of the nation’s 824 treatment plants discharge untreated or partially treated sewage into our limited water resources. As of June 2023, the Department of Health had documented 1,045 suspected cholera cases across five provinces, with 197 cases confirmed by laboratory testing, directly linked to compromised water supply.
This crisis disproportionately impacts both urban and rural regions, where access to clean water and sanitation remains a pressing concern. Impoverished communities often rely on highly polluted water sources contaminated by sewage from overwhelmed treatment plants, further straining water purification efforts to meet safety standards. Recognising the intrinsic connection between drinking water quality and wastewater treatment is crucial, necessitating immediate attention and resolution.
However, a significant challenge faced by South African communities is the prohibitive cost of implementing waterborne sanitation solutions everywhere. With over four million latrines and roughly 50 million people lacking adequate sanitation, conventional waterborne systems are neither viable nor cost-effective comprehensive solutions.
South Africa’s water quality reports: red flags aplenty
The Blue Drop Report 2023, released in June 2023, paints a concerning picture of South Africa’s drinking water quality. While major cities maintain safe water, outlying areas face contamination and infrastructure challenges. Key statistics from the report reveal that the average Technical Site Assessment (TSA) score for water treatment systems is 69%, indicating partial functionality. About 15% of water supply systems are in poor or critical condition, with only 33% having Water Safety Plans, posing significant risks to water quality. Additionally, 50% of municipalities struggle with bad or poor microbiological water quality.
Wastewater and water wasting: two major risks
The 2023 Green Drop Report assesses wastewater treatment systems, showing a decline with an average score of 50%. Regional disparities persist, with Eastern Cape and Limpopo scoring lowest, while the Western Cape and Gauteng lead. The No Drop Report examines water losses, revealing a decline in overall performance in 2023, with an average score of 65%, which means that one-third of supplied water is wasted before it reaches consumers.
These reports collectively underline the urgent need to enhance drinking water quality in South Africa. Municipalities must focus on prioritising infrastructure maintenance and upgrades, implement risk-based water quality management, and strengthen compliance with standards. The Department of Water and Sanitation must offer more support to municipalities. Failing wastewater treatment facilities exacerbate drinking water purification, risking tap water safety and triggering further potential health and environmental crises. Therefore, they must take steps to safeguard water quality and address sewage infrastructure issues.
Rapid crisis intervention required
South Africa’s sewage crisis is a dire challenge that requires immediate action and innovative solutions. In recognising the inextricable link between sewage waste management and water quality, we must also acknowledge that this crisis cannot only be addressed by government without support from private sector industry leaders and experts. Portable water treatment package plants are available, along with small filtration and sterilisation systems for communities. Wastewater packaged treatment plants and solutions can help both alleviate immediate concerns and contribute to long-term sewage management strategies. Further neglecting the sewage problem and the critical maintenance of existing infrastructure will only deepen our water crisis. For this reason, the government needs to prioritise investment in sewage treatment infrastructure and implement practical, affordable solutions across all communities.
Mitigating South Africa’s sewage crisis
If municipal water supplies deteriorate further, sanitation specialists will be required to step in with a range of interventions. These extend from portable water treatment packaged plants to improve water quality at its source, to small-scale filtration and sterilisation systems designed for household use to ensure safe drinking water directly from the tap. From a contamination perspective, it is critical to reduce sewage entry into water courses, particularly in rural areas and informal settlements. This can be achieved through enhanced sanitation solutions, such as dry sanitation toilets, which are waste-contained alternatives to pit latrines.
From immediate relief to sustainable futures
Interventions will need to consider both immediate and long-term strategies. For short-term relief, containerised package plants can bolster sewage treatment facilities without the need for extensive infrastructure development, alleviating the strain on existing systems. Simultaneously, sanitation providers in the private sector can aid municipalities in implementing long-term solutions, including megalitre plans that feature efficiently packaged treatment plants. By adopting these smaller, cost-effective alternatives, it is possible to achieve the same capacity traditionally associated with larger concrete plants, in a fraction of the time to avert total system collapse and the impending health and economic catastrophes that would surely follow.
As of Sunday, reports indicate that 23 people have died so far in the recent cholera outbreak in Hammanskraal, a direct result of the town’s neglected water sanitation infrastructure. A further 48 have been hospitalised, with six emergency field tents being set up to prop up the overburdened Jubilee Hospital, which has seen 215 patients since 19 May, as reported in the most recent Gauteng Department of Health bulletin.
The temporary field hospital has been set up to immediately attend to cases of dehydration, supplying oral rehydration solution (IRS) as well as intravenous fluids. More critical patients are taken to Tshwane hospitals.
The Gauteng Department of Health also notes that as of Friday, 27 of the 75 confirmed cholera cases had recovered and been discharged. The Gauteng Department of Education has said that it will intensify efforts to supply schools in Hammanskraal with clean drinking water.
South Africa’s most serious outbreak of cholera in recent history was from November 2008, when a massive cholera outbreak occurred in Zimbabwe and spread to South Africa. Within the first 5 months of the outbreak, more than 73 000 cases and 3500 deaths (case fatality rate of >4.7%) had been reported, and it spread to South Africa through Musina. Between 15 November 2008 and 30 April 2009, a total of 12 706 cases of cholera were reported by the National Department of Health. Of the total number of cases, 1114 (9.0%) were laboratory-confirmed cases, and 65 deaths (case fatality rate of 0.5%) were recorded. In this outbreak, microbial analysis published in the Journal of Infectious Diseases found the emergence of antimicrobial resistance in Vibrio cholerae 01 strains.
The National Institute of Communicable Diseases has posted guidelines [PDF] for the management of suspected cholera chases.
Almost 100 former nurses at Jubilee District Hospital in Hammanskraal are calling on the Gauteng Department of Health to employ them permanently. Originally contracted in July 2020 to deal with the Covid pandemic, their employment contracts were periodically renewed but terminated at the end of March 2023.
The nurses have been sitting outside the hospital since Monday.
“They want us to work under agencies, and we don’t want that,” said a nurse.
“This hospital is very understaffed, but they are being stubborn. Inside the wards there are only two nurses working, and they are overstretched. They are struggling but the department doesn’t want to employ more nursing staff,” she said.
“It’s heartbreaking to see our people in distress, and I know I am a qualified person and could help. We are told there is no budget for us,” she said.
In a statement on Monday, the Democratic Nursing Organisation of South Africa (DENOSA), said as a result of the cholera outbreak “Jubilee Hospital is now experiencing an influx of patients, which is stretching the facility to breaking point.”
“Nurses in the facilities in the area will also be made to perform duties that are outside their scope of practice where they may be expected to carry water buckets to the water tankers. DENOSA does not encourage that nurses perform duties that are outside their scope.”
DENOSA Gauteng provincial secretary Bongani Mazibuko said there was a shortage of nurses and that it had been agreed at the provincial level to extend the contracts of Covid contract nurses.
Mazibuko said the contracts were due to end on the 31 March 2023 and the Gauteng health department was supposed to have given the nurses new contracts for 1 April 2023 to March 2024.
He said nurses whose contracts had been terminated should contact the union.
GroundUp made several attempts, all in vain, to get comment from the Gauteng health department.
Scanning electron micrograph image of Vibrio cholerae. Source: Wikimedia CC0
The Hammanskraal cholera outbreak continues with 17 deaths from the disease reported so far. Poverty is exacerbating the situation, with residents being advised to drink bottled water – but unable to afford it. According to GroundUp, the microbiological compliance (a measure of faecal bacteria) at sewage treatment plants was as low as 2% and 0%, where below 50% is considered ‘bad’.
Characterised by watery diarrhoea and dehydration, cholera is caused by infection by the bacterium Vibrio cholerae and in some cases can cause death within hours. It is spread through contaminated water, and asymptomatic individuals can contribute to the spread by shedding bacteria in faeces for seven to 14 weeks.
The National Institute for Communicable Diseases (NICD) says that treatment is with oral rehydration solution (ORS), with intravenous ringer’s lactate for severe dehydration and antibiotics recommended in hospitalised patients.
For acute cases of watery diarrhoea, the National Institute for Communicable Diseases (NICD) advises the following course of action:
– Notify the case as suspected cholera by completing a Notifiable Medical Conditions case notification form. Do this immediately; don’t wait for laboratory results.
1. Assess and reassess the degree of dehydration frequently.
2. Replace fluid and maintain hydration status based on the degree of dehydration (see flowchart)
3. Antibiotic therapy is recommended for hospitalised patients. Ciprofloxacin is currently the antibiotic of choice: Paediatric dose: 20 mg/kg (max 1g) po stat Adult dose: 1g po stat
4. Children < 5 years of age should be given zinc supplementation.
5. Patients should be fed as soon as they can tolerate food
6. Patients who are no longer dehydrated and can take ORS and have decreased frequency of diarrhoea may be discharged.
Scanning electron microscope image of Vibrio cholerae bacteria, which infect the digestive system. Zeiss DSM 962 SEM T.J. Kirn, M.J. Lafferty, C.M.P Sandoe and R.K. Taylor, 2000, “Delineation of pilin domains required for bacterial association into microcolonies and intestinal colonization”, Molecular Microbiology, Vol. 35(4):896-910 Copyright: Darthmouth College Electron Microscope Facility / These images are in the public domain
The natural ability of bacteria to adapt to various environmental stimuli can also make them resistant to drugs that would kill or slow their growth. In an article published in PLoS Genetics, microbiologist Dr Salvador Almagro-Moreno uncovers the evolutionary origins of antimicrobial resistance (AMR) in bacteria. His studies on the cholera-causing bacterium Vibrio cholerae show that mutations in a bacterial membrane protein, OmpU, are linked to developing antimicrobial resistance.
These findings provide insight into deciphering what conditions must occur for infectious agents to become resistant.
Dr Almagro-Moreno studied genetic variants of a protein found in bacterial membranes called OmpU. Using computational and molecular approaches, his team found that several OmpU mutations in the cholera bacteria led to resistance to numerous antimicrobial agents. This resistance included antimicrobial peptides that act as defences in the human gut. The researchers found that other OmpU variants did not provide these properties, making the protein an ideal system for deciphering the specific processes that occur to make some bacteria resistant to antimicrobials.
By comparing resistant and antibiotic sensitive variants, the researchers were able to identify specific parts of OmpU associated with the emergence of antibiotic resistance. They also discovered that the genetic material encoding these variants, along with associated traits, can be passed between bacterial cells, increasing therisk of spreading AMR in populations under antibiotic pressure.
By understanding how mutations occur, researchers can better understand and develop therapeutics to combat resistant infections. Dr Almagro-Moreno is also looking at environmental factors such as pollution and warming of the oceans, as possible causes of resistant bacteria. “We are studying the genetic diversity of environmental populations, including coastal Florida isolates, to develop a new approach to understanding how antimicrobial resistance evolves,” he explained.
Understanding the bacteria that causes cholera, an acute diarrhoeal illness linked to infected water and foods, has global implications. The disease sickens up to 4 million people worldwide and severe cases can cause death within hours.
