Last week the CDC reported a positive polio case in an individual from Rockland County, New York. The CDC also announced traces of the same strain of polio were found in New York wastewater as far back as June, a month before the first case emerged. According to the New York State Department of Health, the young man infected was unvaccinated and has since developed serious paralytic poliomyelitis (serious polio paralysis).
Although there is no cure for polio, it was essentially eradicated in 1979 in the US thanks to a vaccine. The vaccine used in the US and the UK is 99% effective, uses inactive polio and is administered during childhood. When contracted, polio can cause muscle weakness, paralysis, permanent disability, and death. However, the majority of polio infections are asymptomatic or mild. Unfortunately, polio is incredibly infectious and has an incubation period that can last 2-3 weeks making it a major public health concern. These qualities enable the rampant spread of polio throughout a community undetected. While there have not been any new cases of polio reported, the traces in the community’s wastewater suggest there may be others shedding the virus in their stool over the past few months. Since paralytic poliomyelitis is a rare symptom, affecting approximately 1% of individuals with polio, health officials have stated there may be hundreds of asymptomatic cases in the population and are urging anyone unvaccinated to get the vaccine immediately.
Accurately determining the infection rates in an area, especially for diseases that can be largely asymptomatic, is one of the biggest challenges epidemiologists must overcome. To estimate rates, many epidemiologists analyze the communal sewage of their region. Following the COVID-19 pandemic, demand for water surveillance increased and many governments took this as an opportunity to establish infrastructure for other disease surveillance, including polio and monkeypox. In order to analyze the sewage, it is combined at wastewater facilities so that culturing, PCR, or metagenomics-based sampling of one sample of the water can detect pathogens at the population level. While this approach is not individually patient specific, it allows for sampling large swathes of the population. This approach also allows the detection of circulating pathogens before patients with symptoms show up at clinics, and therefore gives health experts time to fight the virus before outbreaks occur.
The gold standard for poliovirus detection in wastewater samples is with cell culture and reverse transcription polymerase chain reaction (RT-PCR). First, sewage sludge is filtered in large quantities to remove debris. The viruses in the sludge can then be concentrated to reduce the volume to a minimum by filtration, flocculation, precipitation, or centrifugation. The eluated volume is then analyzed by tissue culture and the viruses present undergo intratypic characterization using RT-PCR to determine the viral type or strain.
As the need for environmental testing continues, it is expected to drive greater demand for the RT-PCR market in 2022. Even if polio vaccination rates increase, wastewater testing will remain important in the monitoring of any possible vaccine-resistant polio variants that could emerge. The market for RT-PCR is assessed in the recently published SDi Global Assessment Report 2022. The report examines the RT-PCR market in the context of the overall PCR market in order to provide information on the market size, vendor share, and forecasts by product type, region, end market and application. In the next few weeks, SDi will publish a more in-depth review of the PCR market which will cover traditional PCR, RT-PCR, and digital PCR.