By Lilita Gcwabe.
Cape Town health authorities have intensified disease surveillance after the National Department of Health announced on Friday that two different poliovirus strains had been detected in wastewater sampled from a treatment plant in the city.
The detections were identified through routine environmental surveillance conducted by the National Institute for Communicable Diseases (NICD), which monitors wastewater and other water resources for signs of emerging diseases and viral variants before clinical cases appear.
According to the department, the strains detected were vaccine-derived poliovirus Type-3 (VDPV3) and novel oral poliovirus vaccine Type-2-like (nOPV2-L). However, health officials stressed that no human cases of polio have been identified and that the findings do not indicate an outbreak.
“These detections are called ‘vaccine events’ because no actual cases of the virus have been detected in a human being,” the department said.
It added that while the findings require a public health response, they are considered low risk and do not warrant an additional vaccination campaign at this stage.
South Africa was certified polio-free by the World Health Organization’s African Regional Certification Commission in September 2019.
Health authorities believe the viruses detected in the wastewater are likely linked to individuals vaccinated in countries that use different polio vaccines from those administered in South Africa.
Responding to questions, Western Cape Department of Health and Wellness spokesperson Dwayne Evans confirmed that provincial authorities were aware of the detections and were working closely with national health officials and the NICD.
“At this stage, the specific wastewater treatment plant and the communities it serves have not been publicly confirmed, while the public health investigation and response processes are under way,” Evans said.
“The department will provide further information where appropriate and in line with the national public health response.”
He emphasised that no confirmed human case of polio had been detected.
“The wastewater detection is being treated as an early warning signal. Wastewater surveillance is specifically designed to detect possible public health risks early, sometimes before any person becomes ill,” Evans said.
The Western Cape Department of Health and Wellness said current response measures include strengthened surveillance, increased environmental sampling, further laboratory testing, and follow-up investigations where clinically indicated.
Authorities are also verifying the latest localised vaccination coverage figures and have reiterated the importance of routine childhood immunisation as the most effective protection against polio.
“Concerning vaccination coverage, the department is verifying the most recent localised data and will share confirmed figures once available. Routine immunisation remains the most important protection against polio. Areas with lower immunisation uptake are routinely prioritised through existing primary healthcare and outreach services,” Evans said.
While the national department suggested the viruses may have originated from imported cases, provincial authorities said it was too early to determine a specific source.
“The Western Cape Department of Health and Wellness is not able to confirm the source of the detections at this stage. Further investigation is under way, and it would be premature to speculate on a specific source or route of introduction,” Evans said.
Health authorities have urged residents not to panic but to ensure that children are up to date with their vaccinations.
“Our message to residents, especially parents and caregivers, is clear: there is no need to panic, but it is important to ensure that children are up to date with their routine immunisations,” Evans said.
Parents who are unsure of their children’s vaccination status have been encouraged to consult their Road to Health Booklet or visit their nearest clinic for advice.
Residents have also been advised to seek medical attention if a child develops sudden weakness in the arms or legs, particularly if accompanied by fever or a recent illness.