This article by Rosemary Rochford is republished here with permission from The Conversation. This content is shared here because the topic may interest Snopes readers; however, it does not represent the work of Snopes fact-checkers or editors.
In the mid-20th century, the fear of polio gripped the United States. Parents were afraid to send their children to birthday parties, public pools, or other places where children would socialize. Children in wheelchairs were stark reminders of the disease’s devastation.
To prevent polio outbreaks, government officials employed tactics now familiar in the COVID-19 era: they closed public spaces and shut down restaurants, swimming pools, and other gathering places.
In 1952, two years before an experimental polio vaccine was introduced, there were an estimated 58,000 cases of polio and 3,145 deaths from polio in the United States. Among them were children who were paralyzed for life. However, these numbers dropped dramatically after a widespread polio vaccination campaign that began in 1955.
In the 1970s, there were fewer than 10 cases of paralysis due to polio in the United States, and poliovirus was considered eradicated from the United States by 1979. Since then, the collective fear of the virus has largely faded – many people alive today are fortunate not to know anyone with polio.
When news broke in July 2022 that an unvaccinated adult male in New York had contracted polio – the first case in the US since 2013 – and was becoming paralyzed by the disease, it sparked a wave of fear throughout the public health community and raised the question of whether an old enemy is making a comeback.
I am a virologist and professor of immunology and microbiology and have spent my career teaching and researching how viruses can cause disease.
There is no cure for polio. The only treatment is prevention. And the means of prevention is vaccination, the same means that eradicated polio in the US in the first place.
Polio virus life cycle
Polio – or poliomyelitis – the disease is caused by the poliovirus, which is passed from person to person through the mouth. And while no one would knowingly pick up a virus, touching a contaminated object like a spoon or glass, or accidentally swallowing contaminated water can unknowingly lead to infection.
When someone is infected with the polio virus, they pass the contagious virus in their feces. For this reason, recent reports that poliovirus has been circulating in New York City’s sewage for months and that the virus has now been detected in three New York boroughs are of particular concern.
In August 2022, New York State Health Commissioner Mary Basset said the state health department “is treating the individual case of polio as just the tip of the iceberg with a much larger potential spread.”
“Based on past polio outbreaks,” she added, “New Yorkers should know that for every observed case of paralytic polio, there may be hundreds of other people infected.”
A single case of polio reflects a greater potential spread of the virus, as most of those infected either show no symptoms or have very mild illness with flu-like symptoms. But even without symptoms, an infected person still sheds viruses in their feces, meaning they can be a source of infection for others.
The virus, which is very stable in the environment, is easily spread through surface contamination. For this reason, hand washing is an important prevention tool. Although many disinfectants, such as alcohol or diluted Lysol, do not inactivate the virus, chlorine bleach destroys it. For this reason, decades ago, health officials began chlorinating swimming pools to inactivate the poliovirus.
Typically, the human body uses stomach acid to protect itself from ingested viruses. But the poliovirus can survive stomach acid to get into your gastrointestinal tract. There the virus reproduces to establish an infection.
What is paralytic polio?
Unfortunately, one person in about 200 people infected with the poliovirus will develop paralysis. Scientists still don’t know why one person is susceptible to paralytic disease, but most don’t.
In the small subset of people who get paralytic polio, the virus can attack the lower motor neurons in the brainstem and spinal cord, which are important for muscle control. Infection of these neurons leads to the muscular paralysis characteristic of paralytic polio. Typically, the legs are affected — often on just one side of the body — and paralysis can range from mild to severe. Other muscle groups can also be affected.
In the worst cases of paralytic polio, the virus can damage the centers of the nervous system that control breathing. Ventilators known as “iron lungs” were early medical devices that helped people with damaged breathing muscles breathe until their muscles healed enough to work independently. Patients could die if the paralysis was severe and persistent.
degrees of severity
Although polio can be devastating to those who contract the severe form of polio, most people’s immune systems are well equipped to fight it off. When someone recovers from polio, researchers can detect antibodies that fight poliovirus in the blood.
But even long-term survivors of paralytic polio can develop late-onset muscle weakness and fatigue known as post-polio syndrome. While the muscular effects of post-polio syndrome are well known, a number of other symptoms can be associated with post-polio syndrome, including chronic pain, trouble sleeping, cold intolerance, and difficulty swallowing.
Because post-polio syndrome is diagnosed based on symptoms only, there is no consensus on the number of polio survivors who develop it, but estimates range from 15% to over 80%.
Polio prevention is key
The decline in polio in the US and worldwide is a direct result of the introduction of vaccines and the public’s willingness to accept them. In 1988, the World Health Organization, in partnership with Rotary International, the Centers for Disease Control and Prevention, and other national governments, launched the Global Polio Eradication Initiative with the goal of eradicating polio, like smallpox, from around the world.
When this initiative began, there were an estimated 350,000 children living with polio in 125 countries. In 2021 there were only six reported cases.
Two types of polio vaccine are used worldwide. The one used in the US since 2000 is an injection of inactivated poliovirus. Inactivation kills the virus and prevents it from spreading. Children in the US receive this vaccine at ages 2 months, 4 months, and between 6 and 15 months, and it provides essentially lifelong protection against polio.
The second type of vaccine, still used in many parts of the world, is an attenuated — or weakened — form of the virus that is taken orally. In places where community transmission is still significant, like Pakistan, the oral vaccine is preferred because it prevents people from contracting polio and also stops human-to-human transmission. In the US, where there has been virtually no human-to-human transmission of poliovirus for decades, the inactivated vaccine is preferred because the focus is on preventing disease in the vaccinated individual and there are fewer concerns about spreading the virus.
But in extremely rare cases, the vaccine virus mutates after being passed in the feces. And when immunization levels fall below a critical threshold – as is the case in some regions of the world – this poliovirus can cause disease. The recent case of polio in New York has been traced to a mutated vaccine-derived poliovirus believed to have been acquired abroad.
Most people in the US are vaccinated through routine childhood vaccinations. Because immunity to polio is lifelong after vaccination, the CDC does not recommend booster shots for the general population for individuals who have completed the full series. However, the CDC recommends that everyone who has not been vaccinated against the poliovirus should get vaccinated, including adults.
In my office I keep a painting of Dr. Jonas Salk, the virologist who developed the first polio vaccine. It serves as a reminder to me of the importance of biomedical research in eradicating the human suffering caused by infectious diseases.
Rosemary Rochford is Professor of Immunology and Microbiology at the University of Colorado Anschutz Medical Campus
This article is republished by The Conversation, a nonprofit, independent news organization dedicated to unlocking the knowledge of experts for the benefit of the public.
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