How Polio Came Back to the U.S. — ProPublica

Update, July 26, 2022: This story has been updated to reflect preliminary results from the wastewater tests.

About a month ago, British health authorities announced that they had found evidence of a local outbreak of polio in London.

Of course, it was a shock. The country was declared polio-free in 2003.

But at least no one got hurt. The evidence comes from routine tests of sewage samples, which alert health officials to the spread of the virus and allow them to intervene quickly. Based on the genetic analysis of those samples, British officials contacted families whose children under the age of 5 were not fully vaccinated and started protecting the city’s children.

The first outbreak of polio in the United States in nearly a decade, confirmed late last week by health officials in New York, will be very different.

In the US, public health agencies do not test sewage for polio. Instead, they wait for people to get sick in doctors’ offices or hospitals — a reactive strategy that gives the stolen virus more time to spread silently through the community before it’s detected.

The first sign of trouble in New York came in June when a young man in Rockland County sought medical attention for weakness and paralysis. Almost a month passed before tests confirmed that he had polio.

Because most polio infections cause no symptoms, between 100 and 1,000 infections can occur at the time of paralysis, said Dr. Yvonne Maldonado, professor of pediatrics at Stanford School of Medicine, chairs the American Academy of Pediatrics’ Committee on Infectious Diseases.

“If you wait for a case to come up, you’re chasing your tail,” he said.

Only after the case was identified did New York health officials begin surveillance, testing sewage samples from Rockland County and beyond to determine if and where the virus was spreading. Like many parts of the US, New York has been collecting sewage and testing it to control the spread of COVID-19. Health officials said they are now testing the stored samples for signs of polio. They say they have detected polio in several samples from Rockland County, but more analysis is needed to understand what the initial results mean.

For decades, the costs of controlling sewage for diseases like polio far outweighed the benefits.

Because of the high vaccination rate in the US, over 90%, the risk of such diseases has been remarkably low, but pockets of the population have long been low. Rockland County, in the northwestern suburbs of New York, is one such place. In 2018 and 2019, he suffered a prolonged outbreak of measles, another vaccine-preventable disease, concentrated mainly in the Orthodox Jewish community, where many refused vaccines. Several news organizations reported that the person with polio was a member of that community.

At the national and global level, there are signs that the pandemic has opened up new vulnerabilities to long-lasting diseases. Routine vaccinations have been hampered by many obstacles, including barriers related to COVID-19 and growing vaccine resistance due to misinformation and politicization. The percentage of children worldwide receiving all three doses of the diphtheria, tetanus and pertussis vaccine fell by 5 percentage points between 2019 and 2021, according to a recent analysis by UNICEF and the World Health Organization. The organizations say this is the most sustained decline in childhood vaccinations in nearly 30 years.

This may have caused the first half of the 20th century U.S. polio scare, highly contagious and life-threatening, polio has historically mostly affected young children, attacking their spinal cord, brain stem, or both.

The virus is spread by faecal material or respiratory droplets from infected people in water or food or on the hands of other people, who then put it in their mouths. It may seem unusual, but it’s one of the most common ways viruses spread, especially among children.

About 70% of infected people have no symptoms, but can spread it to others. Most patients have mild symptoms such as fever, sore throat, muscle weakness and nausea. However, about 5 out of 1,000 patients develop irreversible paralysis.

At its peak in 1952, polio killed more than 3,000 Americans and paralyzed more than 20,000. Pictures of children wrapped in coffin-like metal lungs have frightened parents. After the first polio vaccine was approved in 1955, these concerns were quickly dispelled. Within two years, the number of cases was reduced by 90%.

Since 1988, when the Global Polio Eradication Initiative began providing billions in immunization campaigns and surveillance around the world, polio has been eradicated in the rest of the world. Naturally occurring wild poliomyelitis remains endemic in only two countries, Pakistan and Afghanistan.

But there is another type of polio, one related to the type of vaccine used in much of the world, especially in 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 weakened live viruses to stimulate the immune system to create protective antibodies.

This will bring a bonus. When a vaccinated person sheds live, weakened viruses in their feces, they can spread to unvaccinated people, causing them to develop protective antibodies as well.

But it also brings risks. In rare cases, when weakened viruses circulate in unvaccinated or unimmunized people, they can sicken unvaccinated people and cause preventable disease. The injectable polio vaccine used in the US contains only inactivated viruses and cannot cause polio.

Cases of vaccine-derived polio have emerged in recent years after global health authorities decided in 2016 to remove a strain of polio from the oral vaccine after it discovered that the wild version had been eliminated. This has led to an increase in the number of children who are not immune to the vaccine-derived version of the strain, type 2. (The injectable form of the vaccine used in the United States protects against all strains of polio.)

Vaccine-derived poliovirus type 2 has been found in British sewage samples. It also infected an unvaccinated Rockland County person, suggesting a chain of transmission from someone who received the oral polio vaccine, New York health officials said.

Officials are still investigating whether the person contracted the virus here or from abroad. The Washington Post 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 man did not travel outside the country during the incubation window.”

Finally, New York health officials are using sewage monitoring to tell more quickly if they have a larger problem, allowing them to test thousands of people for polio infection at once rather than individually, said David Larsen, an epidemiologist and professor at Syracuse University. state wastewater control network, said in an email.

Screening of wastewater for polio has been a staple in developing countries for decades, but it does so in at least a few countries where it is rare and has high vaccination rates.

The U.K. began monitoring wastewater for polio and several other viruses found in the gastrointestinal tract in 2016, a spokeswoman for Britain’s health agency said by email. (He later added the virus that causes COVID-19 to the list.)

Israel has been monitoring sewage for polio since 1989. In 2013, health officials spotted an outbreak of wild polio and began a polio-free vaccine campaign in response. But this year, a young boy was sick with paralysis in the Jerusalem area. Public health officials there found additional infections through sewage testing.

Some US public health officials question the value of such testing here.

“I’ve always been a big supporter of fighting polio in the U.S. and doing it elsewhere where other surveillance systems are flawed,” said Mark Pallansch, who will retire in 2021 after working on the topic for most of his career. Polio Eradication Efforts for the Centers for Disease Control and Prevention.

COVID-19 has sparked interest in wastewater control, prompting cities, states and colleges to launch programs and unlock funding for them.

The CDC sends federal money to health departments in more than 40 jurisdictions to support such monitoring efforts, and works with them to collect data posted on the agency’s National Wastewater Monitoring System website. A spokeswoman 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 is labor and resource intensive, requiring increased public health laboratory capacity, the spokesperson said.

One asset of wastewater monitoring is the ability to quickly turn around to try something new.

In November 2020, the Sewerage Coronavirus Alert Network, based out of Stanford and Emory Universities, began daily monitoring of the COVID-19 virus at California wastewater plants. Monitoring for other pathogens has since been added, including variants of COVID-19, the common respiratory virus RSV, and most recently, monkeypox. Such additions are relatively cost-effective because the network can test for multiple pathogens from a single sample, said Marlene Wolfe, one of the two principal investigators and an assistant professor at Emory’s Rollins School of Public Health.

Adding more tests, Wolfe said, raises the question of whether disease surveillance in this way is of any concern for public health decision-making.

There are many questions about whether the pandemic-induced expansion of wastewater testing will continue. Maldonado, chairman of the American Academy of Pediatrics’ Committee on Infectious Diseases, said the recent polio outbreak is another sign that more surveillance of the disease is important.

“Maybe this is an open call for us to really start building better surveillance networks,” he said.

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