About a month ago, British health authorities announced they had found evidence suggesting the local spread of polio in London.
It was a jolt, to be sure. The country was declared polio-free in 2003.
But at least no one appeared sick. The evidence comes from routine tests of waste samples, which can alert health officials that there is a virus circulating and allow them to intervene quickly. Based on genetic analysis of the sample, officials in the UK are moving to protect city children by reaching out to families with children under 5 who have not been fully vaccinated.
Polio’s first appearance in nearly a decade in the US, confirmed in late July by health officials in New York, will play a very different role.
In the US, public health agencies generally do not test sewage for polio. Instead, they wait for people to show up sick in doctor’s offices or hospitals — a reactive strategy that could give this hidden virus more time to secretly circulate in society before being detected.
In New York, the first signs of trouble appeared when a young man in Rockland County sought medical treatment for weakness and paralysis in June. By the time tests confirmed he had polio, nearly a month had passed.
Because most polio infections are asymptomatic, by the time there is a case of paralysis, 100 to 1,000 infections may have occurred, said Dr. Yvonne Maldonado, a professor of pediatrics at the Stanford School of Medicine who heads the American Academy of Pediatrics. ‘ infectious disease committee.
“You’ve been chasing your tail if you’re going to wait for a case to come up,” he said.
Only after the case was identified did New York health officials begin the kind of surveillance the UK does, testing wastewater samples from Rockland County and beyond to help determine if the virus was spreading and where. Like many parts of the US, New York is already collecting waste and analyzing it to track the spread of COVID-19. Health officials said they were now testing stored samples for signs of polio. They said they had detected polio in some Rockland County samples but needed to analyze more to understand what the initial results represented.
“You’ve already caught up if you’re going to wait for cases to emerge,” said Dr. Yvonne Maldonado.
For decades, the costs of conducting wastewater surveillance for diseases such as polio have clearly outweighed the benefits.
U.S. vaccination rates high levels, reaching 90 percent, make the risk of such a disease very low, although there have long been pockets of the population where rates are much lower. Rockland County, a suburb of northwest New York City, is one of them. It suffered from prolonged outbreaks of measles, another vaccine-preventable disease, in 2018 and 2019 largely concentrated in its Orthodox Jewish community, where many opted out of vaccines. Several news organizations have reported that polio patients are members of that community.
Nationally and globally, there are signs that the pandemic has opened up new vulnerabilities to long-retreating diseases. Routine immunization has been hampered by a number of obstacles, including COVID-19-related lockdowns and rising vaccine resistance fueled by 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 vaccine against diphtheria, tetanus and pertussis – a measure of overall immunization – fell by 5 points between 2019 and 2021 and measles and polio vaccinations. also down. The organization said it was the biggest sustained drop in childhood vaccinations in about 30 years they had collected data.
That could create a greater risk of polio, the scourge of the first half of the 20th century in the US. Highly contagious and potentially life-threatening, polio has historically been the victim of mostly young children, affecting the spinal cord, brainstem, or both.
The virus is spread when fecal material or respiratory droplets from an infected person get into water or food or onto other people’s hands, which they then put in their mouths. This may sound unusual, but it is one of the most common ways the virus circulates, especially among children.
At its peak in 1952, polio killed more than 3,000 Americans and crippled more than 20,000.
About 70 percent of those infected show no signs of illness but can infect others. Of those who do get sick, most have mild symptoms, such as fever, sore throat, muscle weakness, and nausea. But about 5 in 1,000 infected people experience permanent paralysis.
At its peak in 1952, polio killed more than 3,000 Americans and crippled more than 20,000. Images of children encased in iron lungs like coffins terrified parents. Those fears faded quickly after the first polio vaccine was approved in 1955. Within two years, cases fell by as much as 90 percent.
Since 1988, when the Global Polio Eradication Initiative began pouring billions of dollars into immunization and surveillance campaigns around the world, polio has been eradicated in most other parts of the world. Wild polio, a naturally occurring strain, remains endemic in only two countries, Pakistan and Afghanistan.
But there are other types of polio in circulation, which are 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 US since 2000, is easy to administer—just a few drops on the tongue—and inexpensive to make. It uses live, attenuated viruses to trigger the immune system to make protective antibodies.
That brings a bonus. When the vaccinated pass the weak live virus in their stool, they can spread to the unvaccinated, triggering protective antibodies in them as well.
But it also carries risks. In rare cases, when the attenuated virus circulates in people who have not been vaccinated or are under-immunized, the virus returns to a form that can make unvaccinated people sick, causing the disease it would otherwise have prevented. The injectable polio vaccine used in the US contains only the inactivated virus and cannot cause this.
Cases of vaccine-derived polio have spiked in recent years after global health authorities decided in 2016 to remove one strain of polio from oral vaccines after determining that the wild version had been eradicated globally. This leaves a growing number of children without immunity to a vaccine-derived version of that type, Type 2. (The injectable form of vaccine used in the US provides protection against all types of polio.)
The type 2 vaccine-derived poliovirus strain is the type found in UK sewage samples. It was also the strain that infected unvaccinated Rockland County men, suggesting a chain of transmission from someone who received the oral polio vaccine, health officials in New York said.
Officials are still investigating where the man contracted the virus, here or abroad. The Washington Post has reported that the man traveled to Poland and Hungary this year, but a spokesperson for the Rockland County Health Department said in an email, “The person did not travel overseas during the incubation period.”
Ultimately, New York health officials will use wastewater monitoring to quickly tell them whether they have a bigger problem, essentially allowing them to test thousands of people at once for polio infection rather than individually, said David Larsen, an epidemiologist and The Syracuse University professor who directs the state’s wastewater surveillance network, said in an email.
Wastewater testing for polio has been a staple in developing countries for decades, but at least some countries where cases are rare and vaccination rates are high do so too.
The UK began monitoring wastewater in 2016 for polio and some other viruses that occur in the digestive tract, a spokesman for the UK’s health safety agency said in an email. (It has since added the virus that causes COVID-19 to the list.)
Israel has been monitoring waste for polio since 1989. In 2013, health officials were able to detect outbreaks of wild polio just from sampling and launching a vaccine campaign in response without ever experiencing a case of paralysis. However, this year, a small child in the Jerusalem area suffered from paralytic polio. Public health authorities there found additional infections through sewage tests.
Some US public health officials are skeptical of the value of such testing here.
“I’ve always been unenthusiastic about doing it for polio in the US and big supporters of doing it elsewhere, where there are flaws in other surveillance systems,” said Mark Pallansch, who is retiring in 2021 after spending most of his career working on polio eradication efforts for the Centers for Control. and Disease Prevention.
COVID-19 has sparked an explosion of interest in wastewater surveillance, prompting cities, states and colleges to launch programs and open floodgates of funding for them.
The CDC sends federal money 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 Control System website. A spokesperson said in an email that the agency is working to expand the platform to include data on other pathogens, from foodborne infections like salmonella to influenza, but not polio. National polio testing will be labor intensive and resource intensive, requiring increased capacity of public health laboratories, the spokesman said.
One of the assets of wastewater monitoring is the ability to spin quickly to test something new.
In November 2020, the Sewer Coronavirus Alert Network, based at Stanford and Emory Universities, began daily monitoring of a California wastewater plant for the virus that causes COVID-19. It has since added monitoring for other pathogens, including the COVID-19 variant, the common respiratory virus RSV and, most recently, monkeypox. Such additions are relatively economical because tissues can test for many pathogens from a single sample, said Marlene Wolfe, one of the two principal investigators and an assistant professor in the Rollins School of Public Health at Emory.
In adding more tests, Wolfe said, the question is always whether monitoring disease in this way is likely to come up with something of sufficient concern to drive public health decisions.
Many have questioned whether the expansion of wastewater testing sparked by the pandemic will hold up. Maldonado, chair of the American Academy of Pediatrics’ infectious disease committee, said the recent polio cases were another signal that more disease tracking was critical.
“Maybe this is a call to action for us to actually start building a better surveillance network,” he said.
Robin Fields is a ProPublica reporter. He joined ProPublica as a reporter in 2008, became a senior editor in 2010 and was later promoted to managing editor in 2013 before returning to the reporter role.
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