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Finding Polio in Wastewater Samples

Should you be concerned that health officials have found poliovirus in wastewater samples in New York, London, and Jerusalem?

Wild polio is now endemic in just two countries - Pakistan and Afghanistan.
Wild polio is now endemic in just two countries – Pakistan and Afghanistan.

Is everyone in your family vaccinated and protected?

Finding Polio in Wastewater Samples

First things first…

How does polio get in our wastewater?

Since the polio virus is spread by fecal oral transmission, it is easy to understand that if you have polio, then you will shed the virus in your stool, making it is easy to detect by sampling wastewater.

“If a population is seriously under-immunized, there are enough susceptible children for the excreted vaccine-derived polioviruses to begin circulating in the community. If the vaccine-virus is able to circulate for a prolonged period of time uninterrupted, it can mutate and, over the course of 12-18 months, reacquire neurovirulence. These viruses are called circulating vaccine-derived polioviruses (cVDPV).”

Circulating vaccine-derived poliovirus

So if the virus, in this case a type 2 vaccine-derived poliovirus (VDPV2), was detected, does this mean that people in New York, London, and Jerusalem have polio?

“In 2021, 682 cases of cVDPV2 were confirmed from 22 countries, compared to 1,081 cases from 24 countries in 2020.”

Global Circulating Vaccine-derived Poliovirus (cVDPV)

Well, it means that someone in these areas likely had a poliovirus infection, however, since the great majority of people with polio don’t have any symptoms, they may not have known it.

“In summary, VP1 sequences from sewage samples collected in Israel (Sorek Waste Water Treatment Plant), USA (Rockland County), UK (Beckton Waste Water Treatment Plant) and the VP1 sequence from the AFP case in Rockland, showed genetic linkage between the isolates.”

Short report on type 2 polioviruses detected in the USA, ISRAEL and the UK

And although we know that the cases are all somehow related, we don’t know how.

“The most likely scenario is that a recently vaccinated individual entered the UK before February 2022 from a country where oral polio vaccine (OPV) has been used for supplementary immunisation campaigns. While the UK stopped using OPV in 2004, several countries, including Pakistan, Afghanistan and Nigeria have continued to use OPV containing type 2 virus for outbreak control.”

Immediate actions in response to detection of vaccine derived polio virus type 2 (VDPV2) in London sewage samples

But someone in Rockland did develop polio, so is that the source of the virus detected in their wastewater?

“Sequence analysis by the Centers for Disease Control and Prevention (CDC) has found that seven positive samples from both Rockland County (three) and Orange County (four) are genetically linked to the individual case of paralytic polio previously identified in a Rockland County resident.”

Following the Identification of a Paralytic Polio Case in Rockland County, More Virus Found in Environmental Samples in Rockland and Orange Counties – Evidence of Local Transmission

While it would seem easy to make that connection, polio was first detected in the wastewater samples in Rockland County in June 2022, about a month before the person developed polio!

The incubation period for the onset of paralysis is up to 21 days though, but still, we don’t know if they were the source.

“One way to detect polioviruses that are spreading without causing symptoms in regions declared free of the virus is through epidemiological surveillance of wastewater. At wastewater treatment facilities, sewage from an entire region is combined, such that culturing, PCR or metagenomics-based sampling of a single wastewater sample can detect the presence of pathogens at the population level. What this approach lacks in terms of individual patient-level specificity, it makes up for by sampling large swathes of the population. Perhaps more importantly, this approach can detect the presence of circulating pathogens before patients present to clinicians with symptoms, thereby giving public-health experts time to mount defences before outbreaks occur.”

Wastewater monitoring comes of age

More importantly, since most communities do not do wastewater sampling for polio, we really don’t know whether or not this is an even bigger problem. And what a big problem it would be if polio was circulating in more of our communities, considering that vaccination rates have been dropping in recent years!

Adding polio to the WastewaterSCAN system, “a national effort to spread SCAN’s leading approach for monitoring diseases through municipal wastewater systems to inform public health responses locally and nationally,” should help us find out.

Don’t wait though – get your family vaccinated and protected!

Tom Little’s editorial cartoon about an unvaccinated child with polio originally appeared in the Nashville Tennessean on January 12, 1956.
Tom Little’s editorial cartoon about an unvaccinated child with polio originally appeared in the Nashville Tennessean on January 12, 1956.

Why leave your unvaccinated child at risk for a polio infection?

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