About a month ago, British health authorities announced that they had found evidence of a local spread of polio in London.
It certainly was a shock. The country was declared polio-free in 2003.
But at least no one got sick. The evidence came from routine testing of sanitation samples, which can alert health officials to the spread of the virus and allow them to intervene quickly. Based on genetic analysis of those samples, UK officials moved to protect city children by reaching out to families with children under five who had not been fully vaccinated.
The first appearance of polio in nearly a decade in the United States, which was confirmed late last week by New York health officials, would be very different.
In the United States, public health agencies generally do not test wastewater for polio. Instead, they wait for sick people to appear in doctors’ offices or hospitals – a reactive strategy that could give this hidden virus more time to spread silently through society before it’s detected.
In New York, the first sign of trouble came when a young man in Rockland County sought medical treatment for weakness and paralysis in June. By the time tests confirmed he had polio, it had been about a month.
Because the majority of polio infections cause no symptoms, by the time there’s a case of paralysis, 100 to 1,000 infections may have occurred, said Dr. Yvonne Maldonado, a professor of pediatrics at Stanford School of Medicine who chairs the American Academy of Pediatrics. Infectious Diseases Committee.
“You’re already chasing your tail if you’re going to wait for a case to come out,” she said.
Only after the case was identified did New York health officials begin the kind of monitoring the British were doing, testing sewage samples from Rockland County and beyond to help determine if and where the virus was spreading. Like many parts of the United States, New York has already been collecting and analyzing sewage to track the spread of COVID-19. Health officials say they are now testing stored samples for signs of polio. They say they have detected polio in a few Rockland County samples but need to analyze more to understand what the initial findings represent.
For decades, the cost of conducting wastewater monitoring for diseases such as polio has clearly outweighed the benefits.
High vaccination rates in the United States, in excess of 90%, have made the risk of contracting such diseases incredibly low, although there have long been pockets of the population where rates are much lower. Rockland County, a suburban area northwest of New York City, is one such place. She experienced outbreaks of measles, another vaccine-preventable disease, in 2018 and 2019 that was so concentrated in the Orthodox Jewish community that many of the vaccines withdrew. Several news organizations have reported that a polio patient is a member of this community.
Both nationally and globally, there are signs that the pandemic has opened up new vulnerabilities to diseases that have been in decline for a long time. A range of obstacles have hampered routine immunization operations, including COVID-19-related shutdowns and increased vaccine resistance due to misinformation and politicization. A recent analysis by UNICEF and the World Health Organization showed that the percentage of children worldwide who received all three doses of the diphtheria, tetanus and pertussis vaccine – a measure of universal immunization – fell by 5 points between 2019 and 2021 and that measles and polio vaccinations declined Moreover. The organizations say this is the largest sustained decline in children’s vaccines in the nearly 30 years they have been collecting data.
This can increase the risk of polio, a scourge in the first half of the 20th century in the United States, highly contagious and potentially life-threatening, polio has historically been a victim of young children, attacking their spinal cords, brain stems, or both.
The virus spreads when faecal material or respiratory droplets from infected people get into water, food, or into the hands of others, and then put it in their mouths. This may sound unusual, but it is one of the most common ways viruses spread, especially among children.
About 70% of those infected do not show signs of illness but can infect others. Most people who get sick have mild symptoms, such as fever, sore throat, muscle weakness, and nausea. But about 5 out of every 1,000 infected people develop irreversible paralysis.
At its peak in 1952, polio killed more than 3,000 Americans and paralyzed more than 20,000. Pictures of children covered in iron lungs resembling a coffin terrified parents. These concerns quickly faded after the first polio vaccine was approved in 1955. Within two years, cases were down by as much as 90%.
Since 1988, when the Global Polio Eradication Initiative began pumping billions into immunization and surveillance campaigns around the world, polio has been eradicated from much of the world. Wild polio, of the naturally occurring type, is still endemic in only two countries, Pakistan and Afghanistan.
But another type of polio is spreading, one related to the type of vaccine used in much of the world, especially low-income countries. This oral vaccine, which has not been used in the United States since 2000, is easy to use — just a few drops on the tongue — and cheap to make. It uses weakened live viruses to stimulate the immune system to make protective antibodies.
This brings a bonus. When a vaccinator excretes the weakened live virus in its faeces, it can spread to the unvaccinated, causing protective antibodies to appear in them as well.
But it also brings risk. In rare cases, when weakened viruses spread to people who haven’t been vaccinated or who are immunocompromised, they revert to a form that can make unvaccinated people sick, causing the disease that was meant to be prevented. The injectable polio vaccine used in the United States contains only inactivated viruses and cannot cause it.
Cases of vaccine-derived polio have risen in recent years after global health authorities decided in 2016 to remove one strain of oral polio from the oral vaccine after ensuring that the wild version was eliminated globally. This left an increasing number of children without immunity to the vaccine-derived version of that strain, type 2. (the injectable form of the vaccine used in the United States imparts protection against all strains of polio).
Vaccine-derived poliovirus type II is the type found in British wastewater samples. This is the type that infected an unvaccinated Rockland County man, New York health officials said, indicating a chain of transmission from a person who received the oral polio vaccine.
Officials are still investigating where the man contracted the virus, here or abroad. The Washington Post reported that the man traveled to Poland and Hungary this year, but a Rockland County Health Department spokesperson said in an email, “The person did not travel out of the country during what would have been the incubation window.”
Ultimately, New York health officials will use sewage monitoring to quickly tell them if they have a bigger problem, essentially allowing them to test thousands of people simultaneously for polio infection rather than individually, David Larsen, epidemiologist and professor at Syracuse University who operates the state’s wastewater monitoring network, in an email.
Wastewater testing for polio has been a staple in developing nations for decades, but at least a few countries where cases are rare and vaccination rates are high do so as well.
A spokesperson for Britain’s Health Security Agency said via email that the UK began monitoring sewage in 2016 for polio and several other viruses that occur in the gastrointestinal tract. (He has since added the virus that causes COVID-19 to the list.)
Israel has been monitoring polio wastewater since 1989. In 2013, health officials were able to detect a wild polio outbreak only from sampling and launch a vaccine campaign in response without ever experiencing any paralysis. This year, a small child in the Jerusalem area contracted paralytic polio. Public health authorities found additional infections there through sanitation tests.
Some US public health officials have been skeptical of the value of such tests here.
Marc Balanche, who retired in 2021 after spending much of his career working on polio eradication efforts for the Centers for Disease Control and Prevention.
COVID-19 has sparked great interest in wastewater monitoring, prompting cities, states, and colleges to launch programs and unlock funding for them.
The CDC has sent federal funds to health departments in more than 40 jurisdictions to support these tracking efforts, working with them to collect data published on the agency’s National Wastewater Monitoring System website. A spokesperson for the agency said in an email that the agency is expanding the platform to include data on other pathogens, from foodborne infections like salmonella to influenza, but not polio. The spokesperson said nationwide polio testing would be labor- and resource-intensive, requiring an increase in the capacity of public health laboratories.
One advantage of wastewater monitoring is the ability to pivot quickly to test something new.
In November 2020, the Sanitation Coronavirus Alert Network, based at Stanford and Emory Universities, began daily monitoring at California sanitation stations for the virus that causes COVID-19. It has since added surveillance for other pathogens, including variants of COVID-19, RSV, and most recently monkeypox. Such additions are relatively economical because the network can test for many pathogens from a single sample, said Marilyn Wolf, a principal investigator and assistant professor at the Rollins School of Public Health in Emory.
As more tests are added, Wolf said, the question is always whether monitoring the disease in this way is likely to turn up anything of concern enough to make public health decisions.
Many question whether the expansion of testing wastewater fueled by the pandemic will continue. Maldonado, chair of the American Academy of Pediatrics’ Infectious Diseases Committee, said the recent polio case is another sign that more tracking of the disease is critical.
“Maybe this is a clear call for us to really start building better monitoring networks,” she said.