South African health authorities have reassured the public after two different polio virus strains were detected in wastewater samples collected from a treatment plant in Cape Town.
Officials say the findings do not indicate an outbreak and that no human cases of polio have been identified in the country.
The National Institute for Communicable Diseases (NICD) informed the Department of Health of the detection on Friday as part of its ongoing environmental surveillance programme.
According to the department, the wastewater testing forms part of routine monitoring aimed at identifying viruses and emerging disease threats before clinical cases appear within communities.
Health department spokesperson Foster Mohale said the detections were classified as “vaccine events” because the virus traces are believed to be linked to vaccinated individuals rather than active infections spreading locally.
“These events need a public health response, are not high risk and no additional vaccination campaign is required,” Mohale said.
Authorities say no outbreak has been detected
South Africa was officially certified polio-free by the World Health Organization (WHO) in September 2019.
Mohale stressed that the latest findings do not change the country’s status.
He explained that the detected strains may have originated from individuals vaccinated with oral polio vaccines used in other countries, which can sometimes result in weakened vaccine-derived virus traces appearing in wastewater systems.
Public health experts say environmental monitoring has become an increasingly important early-warning tool in disease surveillance worldwide.
By testing sewage and municipal water systems, researchers can detect viral activity before hospitals or clinics report confirmed infections.
The NICD has expanded its wastewater monitoring programmes in recent years as part of broader efforts to strengthen outbreak preparedness following lessons learned during the Covid-19 pandemic.
Although no immediate public health emergency has been declared, scientists say the presence of the virus in wastewater indicates that continued monitoring remains essential.
Scientists highlight broader wastewater concerns
Water scientist Ayesha Laher noted that South Africa’s struggling wastewater infrastructure is not directly responsible for the detection itself, but the findings still raise important public health questions.
“The question was why polio was found in wastewater, because it means that there were people carrying polio in the community, which is a health risk,” Laher said.
South Africa’s wastewater treatment systems have faced growing scrutiny following repeated warnings about ageing infrastructure and poor maintenance standards in parts of the country.
The latest Green Drop report previously highlighted serious operational challenges affecting numerous wastewater treatment plants nationwide.
Researchers are also increasingly using wastewater analysis to study antibiotic-resistant bacteria and other emerging health threats.
Wiida Fourie-Basson, spokesperson for Stellenbosch University’s Faculty of Science, said researchers recently identified genetic material linked to two major groups of bacteria known for high-risk resistance profiles in wastewater samples collected in the City of Tshwane.
Health authorities continue to encourage parents to ensure children receive all routine vaccinations, including protection against polio, as part of South Africa’s national immunisation programme.
Source: Adapted from statements by South Africa’s Department of Health, NICD, and local scientific experts.