Two Polio virus strains detected in Cape Town

Added: 2026-05-22

[00:00:00]The National Institute for Communicable Diseases says it's detected two strains of the polio virus in the Cape Town wastewater treatment plant. The health department says the detection was part of the NICD's routine environmental and wastewater testing they conduct proactive population-wide disease tracking. No human cases have been identified so far. Officials are emphasizing this does not mean there's been an outbreak. Dr. Kerrigan McCarthy is a pathologist at the Centre for Vaccine and Immunology at the NICD. Dr. McCarthy, good afternoon to you. Okay, let's start at the very beginning here. What have you found and what have you not found?

[00:00:40]Fantastic. Um Stephen, we found um uh two strains of uh uh polio virus um that uh are part of our routine wastewater surveillance testing for polio.

[00:00:55]Um what we have not found is any clinical cases of disease due to the same polio viruses. So, there's two kinds of surveillance systems for polio that are implemented by the World Health Organization across the world.

[00:01:10]The first is uh clinical cases where um surveillance for a condition called acute flaccid paralysis is done. That's um a sudden onset of paralysis.

[00:01:22]Um and this surveillance is done by healthcare workers, by clinicians in hospitals and clinics.

[00:01:28]The second kind of surveillance is what we call environmental surveillance. And this is done where we look for the polio virus in wastewater, in wastewater treatment plants, if there are treatment plants or open drains or sewers.

[00:01:41]This second kind of surveillance is particularly helpful because the polio virus infects a large number of people, but only a very small proportion, in fact 1% or less, develop symptoms of disease.

[00:01:55]And so, uh if we able to find it in wastewater, it often gives us an early warning that there may be clinical cases that are asymptomatic in the community or that might still be coming.

[00:02:09]And we are able then to take preventive action.

[00:02:14]Okay, so what should we do now? I mean, it doesn't mean as you say there's no indication that anyone in Cape Town has polio, but we obviously need to have some response.

[00:02:27]Absolutely. So, one of the first things we have to do by the international health regulations is notify the World Health Organization, which has been done.

[00:02:35]We then have to have a meeting with our health officials in the National Department of Health and the provincial government and that happened yesterday.

[00:02:45]At this meeting, we the laboratory presents their findings and we review the statistics for the surveillance for polio both through acute flaccid paralysis and for environmental surveillance for the year-to-date and going back. And then we have to classify the event, the detection of the poliovirus as either an outbreak or as an event that requires investigation. So, in this case it's an event that requires investigation.

[00:03:14]And the investigations that we are in progress in supporting the Western Cape provincial government with along with the National Department of Health and the World Health Organization are threefold. The first is to go back to all the hospitals in the city of Cape Town and examine the records to determine if there have been any cases of acute flaccid paralysis that have been missed.

[00:03:39]The second thing to do is to increase the amount of wastewater or environmental sampling for the next two to three, perhaps even more, months in order to see Um, this finding is a consistent finding or if it was an isolated finding. If it's a consistent finding, then it means that there is a focus of infection in the community um, and uh, there might may need to be a vaccination campaign.

[00:04:06]Uh, the third thing we need to do is to collect uh, stool samples uh, from routine uh, uh, sources. So, people who attend um, the clinics and who um, would otherwise be giving a stool specimen. We need to detect uh, or samples from a small proportion of those people um, to see how widespread um, and in fact if at all we can find these strains in in humans.

[00:04:31]As I mentioned um, about 99% of cases of polio are asymptomatic. So, it might well be that someone um, in the community has an infection with the strain, but they don't have any symptoms. So, those investigations are underway at the moment. Okay, as I understand it, um, we've actually been declared polio free since I think at least 2019. So, I presume, I mean, I'm fairly certain I was uh, vaccinated against polio. I hope my children were.

[00:04:59]Um, don't we have a very high rate of vaccination against this?

[00:05:03]So, very critically important and perhaps the main and the the best reason why uh, this um, deserves uh, this event deserves um, public airing is that the um, there is a vaccination for polio. In fact, polio, which is a devastating illness, can kill children or cause lifelong paralysis, is easily preventable by vaccination.

[00:05:27]Um, we still vaccinate against polio and the world will continue to vaccinate against polio until such time as it could potentially be eradicated. So, vaccination for polio is given in two forms. It's given as an oral polio vaccine at birth and 6 weeks of age.

[00:05:45]And then it's given as part of the hexavalent vaccination series that happens at 6, 10, and 14 weeks, and then a booster at 18 months of age.

[00:05:57]And this vaccine is that's contained in this um hexavalent vaccine is called inactivated polio vaccine. So, children in South Africa who participate in the vaccine the routine vaccination program should well be protected against these strains of polio that we have detected in the environment in the sewers.

[00:06:21]Now, if children have not received their vaccines, they may be at risk for getting infected with polio, and if they are very unlucky, if they are part of that 1%, they may land up going on to get polio disease.

[00:06:37]So, uh and that would mean paralysis. So, what we really want to do through this um early preemptive uh detection by a functional and good surveillance system is to encourage people to check their vaccination status of the children in their environment and in their responsibility, and to go and catch up with their vaccines, to go and get vaccinated. It's never too late to vaccinate.