By the time there is a case of paralysis, 100 to 1,000 infections may have already taken place due to the fact that the majority of polio infections are asymptomatic, according to Dr. Yvonne Maldonado, a paediatrics professor at Stanford School of Medicine and chair of the American Academy of Pediatrics' committee on infectious diseases.
Health organisations rarely check wastewater for polio symptoms, which may have allowed the virus time to spread.
British health officials revealed they had discovered evidence pointing to local polio transmission in London around a month ago. In 2003, polio was deemed eradicated in the nation. However, no one had shown up sick. The evidence came from normal sewage sample analyses, which can notify health officials that a virus is spreading and enable them to take swift action. Officials in the United Kingdom took action to protect the city’s youngsters based on genetic analysis of those samples by contacting families with children under 5 who hadn’t had all recommended vaccinations.
Public health organisations in the US don’t typically test sewage for polio. Instead, they wait for sick patients to present themselves at clinics or hospitals, a reactive tactic that can give the sneaky virus more time to spread covertly before being discovered.
The first indication of problems in New York came in June when a young man in Rockland County sought medical attention for weakness and paralysis. Nearly a month had elapsed by the time tests revealed that he had polio.
“You’re already chasing your tail if you’re going to wait for a case to show up,” Dr. Yvonne Maldonado said.
The British-style surveillance, which involved testing wastewater samples from Rockland County and beyond to assess whether the virus is spreading and in which areas, was only begun by New York health officials after the case was detected. Similar to many other U.S. cities, New York was already gathering and studying sewage to monitor the COVID-19 outbreak. As of right now, stored samples are being examined for polio, according to health experts. They claim to have found polio in a few Rockland County samples, but more analysis is required to determine what the preliminary findings really mean.
Although there have always been areas of the population where vaccination rates are far lower, the United States has high immunisation rates that exceed 90%, making the risk of such diseases extremely low. One such location is Rockland County, a suburb of New York City. It experienced a prolonged measles outbreak in 2018 and 2019.
There are indications that the pandemic has created new disease vulnerabilities both nationally and internationally. Numerous barriers, such as lockdowns due to COVID-19 and rising vaccination resistance fueled by misinformation and partisanship, have made routine vaccines difficult.
The percentage of children worldwide who received all three doses of the diphtheria, tetanus, and pertussis vaccine — a measure of overall immunisation — decreased by 5 points between 2019 and 2021, and measles and polio vaccinations also decreased, according to a recent analysis by UNICEF and the World Health Organization. According to the organisations, in the roughly 30 years they have been gathering data, that is the largest consistent fall in children immunizations.
Polio traditionally has primarily affected young children, damaging their spinal cords, brain stems, or both. It is highly contagious and possibly fatal. When bodily waste or respiratory droplets from infected persons come into contact with water, food, or other people’s hands, which they subsequently put in their mouths, the virus is disseminated. Although it may seem strange, this is one of the more typical ways that viruses spread, especially among children.
About 70% of persons who are afflicted do not exhibit any symptoms of the illness yet are nonetheless contagious. Most people who do get sick have minor symptoms like a fever, sore throat, weakness in their muscles, and nausea. Per 1,000 infected individuals, 5% experience permanent paralysis.
At its worst in 1952, polio left more than 20,000 Americans disabled and over 3,000 Americans dead. Parents were scared by images of youngsters enclosed in iron lungs resembling coffins. After the first polio vaccine was licenced in 1955, those worries quickly subsided. Cases decreased by as much as 90% in just two years.
Polio has been eradicated in a large portion of the remainder of the world since 1988, when the Global Polio Eradication Initiative started investing billions in vaccination programmes and surveillance around the globe. Only two nations—Pakistan and Afghanistan—retain endemic populations of wild polio, the type that develops spontaneously.
However, there is another strain of polio that is currently in circulation, one that is connected to the sort of vaccine that is commonly administered around the world, particularly in low-income nations. Just a few drops on the tongue are all that’s needed to administer this oral vaccine, which hasn’t been administered in the United States since 2000. It’s also inexpensive to produce. It stimulates the immune system to produce defense-enhancing antibodies by utilising weakened live viruses.
That offers a benefit. The weakened live viruses that the immunised shed in their faeces can transfer to the unimmunized, inducing protective antibodies in them as well.
Yet there is a risk involved. In a few rare cases, the weakened viruses revert to a form that can infect unvaccinated people and cause the sickness they were intended to prevent when they circulate in people who have not received the vaccination or are under-immunized. Since it solely includes inactivated viruses, the injectable polio vaccination administered in the United States cannot result in this.
After the removal of one strain of polio from the oral vaccine in 2016 following the determination that the wild form had been eradicated globally, cases of vaccine-derived polio have increased in recent years. As a result, an increasing proportion of kids developed type 2 of the vaccine-derived strain of that illness without any immunity.
The type of poliovirus discovered in the British sewage samples is type 2 vaccine-derived poliovirus. According to health officials in New York, it was also the type that infected the unvaccinated Rockland County man, establishing a transmission chain from someone who had gotten the oral polio vaccine.
Authorities are still looking into whether the man contracted the illness domestically or abroad. According to the Washington Post, the man visited Poland and Hungary this year. However, a representative for the Rockland County Health Department claimed in an email that the individual did not leave the nation during the incubation period.
According to David Larsen, an epidemiologist and professor at Syracuse University who oversees the state’s wastewater surveillance network, wastewater monitoring will eventually allow New York health officials to test thousands of people simultaneously for polio infection rather than individually, enabling them to quickly determine whether they have a larger problem.
For many years, developing countries have routinely tested their wastewater for polio, but it is also done in at least a few developed nations where infections are few and vaccination rates are high.
A spokesman for the British health security agency stated via email that the country started checking wastewater in 2016 for polio and a number of other viruses that affect the gastrointestinal tract.
Since 1989, Israel has kept an eye out for polio in sewage. Without ever experiencing any paralysis, health officials were able to identify a wild polio outbreak in 2013 simply by sampling the area and initiate a vaccination campaign in response. But this year, paralytic polio struck a young youngster in the Jerusalem region. Through sewage testing, local public health authorities discovered additional infections.
The usefulness of such testing in this area has been questioned by certain American public health professionals. A surge in interest in wastewater surveillance has been sparked by COVID-19, prompting initiatives to be launched by cities, states, and colleges as well as an influx of financing.
The CDC collaborated with health departments in over 40 jurisdictions to collect data that is posted on the agency’s National Wastewater Surveillance System website in order to support such tracking initiatives.
In an email, a spokesman stated that the organisation was striving to expand the platform to include information on other pathogens, such as influenza and foodborne illnesses like salmonella, but not polio. The spokeswoman stated expanding the capacity of public health laboratories would be necessary because testing for polio at the national level would be labor- and resource-intensive.
The flexibility to quickly change direction to try something new is one advantage of wastewater monitoring.
The Stanford and Emory universities’ Sewer Coronavirus Alert Network began routinely checking California wastewater treatment facilities in November 2020 for the virus that causes COVID-19. Since then, more pathogens have been monitored for, most recently monkeypox and COVID-19 variations as well as the widespread respiratory virus RSV. Since the network can screen for several diseases from a single sample, such upgrades are relatively affordable, according to Marlene Wolfe, one of the two lead investigators and an assistant professor at the Rollins School of Public Health at Emory.
According to Wolfe, the question of whether monitoring a condition in this way is likely to reveal anything of sufficient concern to influence public health decisions is always present when adding more tests.
Many doubt that the pandemic-driven increase in wastewater testing will continue.
The recent polio case is another another indication that improved disease tracking is essential, according to Maldonado, chair of the infectious diseases committee of the American Academy of Pediatrics.
Parvathy Sukumaran 
