Before the polio vaccine became available in the 1950s, people wary of the disabling disease were afraid to send their children outside to school. As polio resurfaces decades after it was eradicated in the United States, Americans unfamiliar with the dreaded disease need a primer to protect themselves and their young children — many of whom are recovering from the trauma of the Covid-19 pandemic.
What is poliomyelitis?
Polio is short for “poliomyelitis”, a neurological disease caused by a poliovirus infection. Of the three types of wild poliovirus — serotypes 1, 2 and 3 — serotype 1 is the most lethal and most likely to cause paralysis.
Most people infected with poliovirus do not get sick and have no symptoms. About a quarter of those infected may experience mild symptoms such as fatigue, fever, headache, neck stiffness, sore throat, nausea, vomiting and abdominal pain. So, like with Covid-19, people without symptoms can unknowingly spread it when they come into contact with others. But in 1 in 200 people with poliovirus infection, the virus can attack the spinal cord and brain. When it infects the spinal cord, people may experience muscle weakness or paralysis, including in the legs, arms, or chest wall. Poliovirus can also infect the brain, causing difficulty breathing or swallowing.
People can develop post-polio syndrome decades after infection. Symptoms can include muscle pain, weakness and wasting.
People with poliomyelitis may be confined to a wheelchair for life or unable to breathe without the help of a ventilator.
How is polio spread?
The virus that causes polio is spread through the “oral-fecal route,” meaning it enters the body through the mouth through hands, water, food, or other items contaminated with poliovirus-containing feces. Rarely, poliovirus can be spread through saliva and upper respiratory droplets. The virus then infects the throat and gastrointestinal tract, spreads to the blood and invades the nervous system.
How do doctors diagnose polio?
Poliomyelitis is diagnosed through a combination of patient interview, physical examination, lab tests, and a spinal cord or brain scan. Health care providers can send stool, throat swabs, spinal fluid, and other samples for lab testing. But because polio has rarely disappeared in the United States for decades, doctors can’t consider the diagnosis for patients with symptoms. And tests for suspected polio must be sent to the Centers for Disease Control and Prevention, because even academic centers no longer test.
How can poliovirus infection be prevented?
The CDC recommends that all children be vaccinated against polio at ages 2 months, 4 months, 6 to 18 months, and 4 to 6 years, a total of four doses. All 50 states and the District of Columbia require that children attending day care or public school be vaccinated against polio, but some states allow medical, religious, or personal exemptions. The Vaccines for Children program provides free polio vaccinations to children who are eligible for Medicaid, uninsured, or underinsured, or who are American Indian or Alaska Native. Most people born in the United States after 1955 have probably received the polio vaccine. But vaccination rates are dangerously low in some areas, such as New York’s Rockland County, where it’s 60%, and Yates County, where it’s 54%, because many families there claim religious exemptions.
There are two types of polio vaccines: killed, inactivated polio vaccine (IPV) and weakened, live, oral polio vaccine (OPV). IPV is an injectable vaccine. OPV can be given by mouth drops or sugar cubes, so it is easy to administer. Both vaccines are highly effective against paralytic poliomyelitis, but OPV appears to be more effective in preventing infection and transmission.
Both wild poliovirus and live, weakened OPV virus can cause infection. Because IPV is a killed virus vaccine, it cannot infect or replicate, causing vaccine-derived poliovirus or paralytic poliomyelitis disease. Weakened, OPV viruses can mutate and regain their ability to cause paralysis—called vaccine-derived poliomyelitis.
Since 2000, only IPV has been offered in the United States. Two doses of IPV are at least 90% effective and three doses of IPV are at least 99% effective in preventing paralytic poliomyelitis. The United States stopped using OPV because of the 1-in-2,000 risk of paralysis in unvaccinated people receiving OPV. Some countries still use OPV.
Vaccination against polio began in the United States in 1955. Cases of paralytic poliomyelitis declined from more than 15,000 a year in the early 1950s to under 100 in the 1960s and then to less than 10 in the 1970s. Today, poliovirus is most likely to spread where hygiene and sanitation are poor and vaccination rates are low.
Why is polio spreading again?
The World Health Organization declared North and South America polio-free as of 1994, but in June 2022, a young adult living in Rockland County, New York was diagnosed with serotype 2 vaccine-derived poliovirus. The patient complained of fever, neck stiffness and leg weakness. The patient had not recently traveled outside the country and was likely infected in the United States. CDC has since begun monitoring wastewater for poliovirus. Poliovirus genetically linked to the Rockland County case has been detected in wastewater samples from Rockland, Orange, and Sullivan counties, which have been circulating in the community as of May 2022. Non-vaccine-derived poliovirus has also been detected in New York City wastewater.
How do I know if I have been vaccinated against polio?
There is no national database of immunization records, but all 50 states and the District of Columbia have immunization information systems with records dating back to the 1990s. Your state or local health department may also have records of your vaccinations. People vaccinated in Arizona, District of Columbia, Louisiana, Maryland, Mississippi, North Dakota and Washington can access their vaccination records using the MyIR mobile app, and those who received the vaccine in Idaho, Minnesota, New Jersey and Utah can do so. Using the Docket app.
You can ask your parents, your childhood pediatrician, your current doctor or pharmacist, or the K-12 school, college, or university you attended if they have your immunization records. Some employers, such as health care systems, may also keep your vaccination records in their occupational health office.
There is no test to determine if you are immune to polio.
Do I need a polio vaccine booster if I was fully vaccinated against polio as a child?
All children and unvaccinated adults should complete the CDC-recommended four-dose series of polio vaccine. If you got OPV you don’t need IPV booster
Adults who are immunocompromised, traveling to a country where poliovirus is circulating, or at high risk of exposure to poliovirus on the job, such as some lab workers and health care workers, may receive a one-time IPV booster.
How is polio treated?
People with mild poliovirus infection do not require treatment. Symptoms usually go away on their own within a few days.
There is no cure for paralytic poliomyelitis. Treatment focuses on physical and occupational therapy to help patients adapt and regain function.
Why has poliovirus not been eradicated?
Smallpox is the only human virus that has been declared eradicated to date. A disease can be eradicated if it infects only humans, if viral infection induces long-term immunity to re-infection, and if an effective vaccine or other deterrent exists. The more contagious the virus, the more difficult it is to eradicate. Viruses that spread asymptomatically are more difficult to eradicate.
In 1988, the World Health Council decided to eradicate polio by the year 2000. Violent conflict, the proliferation of conspiracy theories, vaccine skepticism, insufficient funding and political will, and poor-quality vaccination efforts slow progress toward eradication, but before the Covid pandemic, the world came very close to polio eradication. During the pandemic, childhood immunizations, including the polio vaccine, declined in the United States and around the world.
To eradicate polio, the world must eradicate all wild polioviruses and vaccine-derived polioviruses. Wild poliovirus serotypes 2 and 3 have been eradicated. Wild poliovirus serotype 1, the most virulent form, remains endemic only in Pakistan and Afghanistan, but vaccine-derived polioviruses are spreading to some African countries and other parts of the world. A staged approach involving the use of OPV, then a combination of OPV and IPV, and then IPV alone may be required to eradicate polio from the planet.
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