Galloping towards zoonotic detection
- Wits University
How a love for horses and understanding the virus that kills them put Prof. Marietjie Venter in the saddle of virology towards One Health.
Distinguished Professor Marietjie Venter knows about horses. She competes in international-level dressage classes, with pictures of her and her German Warmblood horse, Quinta 116, adorning her office wall.
But as a virologist, what also piqued her interest almost three decades ago was why horses were getting so sick from a devastating, virulent virus. African horse sickness, spread by biting midges, was but one example of a vector-borne disease occurring in Africa, causing severe respiratory distress, with a fatality rate of up to 90% in horses.
When animals get sick, it’s not only the threat of it being passed to humans. The consequences are social and economic too. In low- and middle-income countries, the death of donkeys and horses, for example, impacts agricultural trade, food production, and often transportation for livelihoods. Outbreaks in these animals may also be used as an early warning system to predict outbreaks in humans
This sparked Venter’s lifelong interest in studying a range of vector-borne and respiratory diseases. Her PhD in Medical Virology, obtained from Wits, focused on respiratory syncytial virus (RSV), the major cause of pneumonia in babies.
This was followed by a postdoctoral fellowship at the National Institute of Allergy and Infectious Diseases in the USA, investigating how zoonotic mosquito-borne viruses can be transmitted from birds to humans and horses. This was fortuitously at the time when the West Nile virus travelled from Africa to the Americas for the first time.
Upon her return to South Africa, Venter established an extensive One Health surveillance network to detect known and emerging zoonotic viruses in animals, humans and mosquito vectors. This work was globally significant and helped establish Venter as a leading figure in disease surveillance.
There are about 200 firmly identified zoonotic diseases – infectious diseases that have jumped from animals to humans. These pathogens are bacterial, viral, and parasitic, involving unconventional agents that spread to humans through direct contact with infected animals (via the air, bites, and body fluids), animal products such as meat and milk, and the environment, such as water or insect vectors.
“There’s still so much more we need to study because we don’t know nearly enough. What is certain is that zoonoses comprise a large percentage of all newly identified infectious diseases as well as many existing ones,” says Venter.
When people fall ill with viral meningitis, there is a chance they were infected with West Nile virus through a mosquito bite. HIV began as a zoonosis, later mutating into human-only strains. Other zoonoses cause recurring outbreaks (think Ebola in Africa), international incidents such as the current outbreak of a rodent-borne hantavirus on a cruise ship, and catastrophic global pandemics like COVID-19.
Venter doesn’t panic about being bitten by mosquitoes (because often once you’ve been bitten, it’s too late anyway), but advises that we can prevent bites with mosquito repellents such as Peaceful Sleep and Tabard and to take malaria prophylaxis in malaria endemic areas.
“It’s important that when we try to explain, prevent and treat viruses, animals, humans and the environment must be considered as a whole. This is what is meant by the ‘One Health’ approach. When patients come to the hospital with infectious diseases, their journey started long before that with exposure to pathogens in the environment, infected animals or other humans.”
Venter led the World Health Organization’s global expert group investigating the origins of SARS-CoV-2, the virus responsible for COVID infections. The group’s final report found that the virus likely emerged from bats via intermediate hosts (whose identities remain unknown), but that critical information regarding the lab accident hypothesis was unavailable.
Whether the epidemic originated from a lab leak cannot be ruled out, but most scientific evidence points to a zoonotic origin, with the first cases occurring around the Huan animal market in Wuhan, China.
Closer to home, Venter was a key member of the National Genomic Surveillance Consortium on COVID-19, which identified the Omicron variant and garnered international interest. Her group also identified the first cases of reverse zoonoses, in which humans infected lions, jaguars and pumas in Africa. Spillback to animals poses a risk of new variants evolving, which can spark new epidemics.
South Africa’s health surveillance networks are world-class, established by the country’s top virologists, veterinarians, doctors, and ecologists to closely track emerging and zoonotic viruses.
“Our technology is state-of-the-art to accurately determine the risk and pathogenesis of new viruses. This informs animal and human health globally,” she says.
Zoonotic diseases that may cause outbreaks in humans and animals through environmental exposure require careful biocontainment, technical rigour, and close integration with an urgent public health response.
In addition to describing viruses such as West Nile Virus and SARS-CoV-2 in humans and animals, Venter and her colleagues have also described influenza and RSV strains, as well as various other zoonotic viruses of interest to human and animal health.
After a prolific career as a zoonotic arbo and respiratory viruses specialist at various high-profile institutions, Venter joined the Infectious Disease and Oncology Research Institute (IDORI) as a Distinguished Professor and NRF SARCHi Chair in Emerging Viral Threats, One Health Surveillance and Vaccines (EViTOH).
Her goal is to strengthen South Africa’s capacity to detect, understand and respond to emerging and re-emerging pathogens, especially vector-borne and respiratory viruses.
Venter was awarded the Royal Society of South Africa’s Marloth Medal 2026 for her highly distinguished contributions, global leadership and service to the furtherance of science.
She met the Dean of the Faculty of Health Sciences at Wits, Professor Shabir Madhi, in the early 2000s when he was a practising paediatrician. Their shared interest in RSV in children formed an early scientific link between molecular virology and clinical disease burden. She credits her professional relationships with Madhi and other internationally renowned scientists, including Professors Barry Schoub and Lynn Morris, both affiliated with the National Institute for Communicable Diseases and Wits, for broadening the scope of her work and encouraging her to look beyond disciplinary boundaries when investigating the origins of disease.
Today, Venter has contributed to building the systems needed to meaningfully detect and respond to illnesses. Her added expertise in establishing a Biosafety Level 3 (BSL-3) zoonotic, arbo and respiratory virus laboratory is an asset to the new Wits Interdisciplinary and Translational Science (WITS) BioHub, which, at 28,000 square metres, will house advanced biomolecular laboratories and a BSL-3 facility for infectious disease research.
“Wits has a strong vaccine culture, with exceptional scientists who collaborate and make their research matter to the world,” says Venter.
While work on pathogen surveillance in mosquitoes and wastewater enables early detection of pathogens in the environment, genomic and vaccine research on emerging and zoonotic causes of pneumonia and meningitis, with high-containment lab capacity, allows EViTOH at Wits not just to spot them, but to be ready to move quickly.
Venter has been preparing for this her whole career.