The anxiety was heightened even further after New York state health officials issued a more urgent call Thursday for unvaccinated children and adults to get inoculated against polio, citing new evidence of possible "community spread" of the dangerous virus.
The polio virus has now been found in seven different wastewater samples in two adjacent counties north of New York City, health officials said.
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Polio, once one of the nation's most feared diseases, was declared eliminated in the United States in 1979, more than two decades after vaccines became available.
Here's everything you need to know about the virus.
What is polio?
Polio, or poliomyelitis, is a disabling and life-threatening disease caused by an enterovirus called the poliovirus. There are three strains, two of which have been eliminated in the world, according to the Global Polio Eradication Initiative, a WHO program.
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An ancient virus, polio has crippled and killed humans for centuries. Etchings on Egyptian vessels show people with withered legs on crutches.
Striking children younger than five the hardest, the worst form of the virus causes nerve injury that can lead to paralysis, difficulty breathing and death. During 20th century epidemics, the virus often struck in warm summer months, sweeping through towns and cities every year or so.
Polio was one of the world's most feared diseases until Dr. Jonas Salk invented the polio vaccine and tested its safety in 1954.
What are the symptoms of polio?
Most people who get infected with poliovirus (about 72 out of 100) will not have any visible symptoms, according to the Centers for Disease Control.
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They say about one out of four people (or 25 out of 100) with poliovirus infection will have flu-like symptoms that may include a sore throat, fever, tiredness, nausea, headache and stomach pain. These symptoms usually last two to five days, then go away on their own.
A smaller proportion of people (much less than one out of 100, or 1-5 out of 1000) with poliovirus infection will develop other, more serious symptoms that affect the brain and spinal cord. That includes paresthesia (feelings of pins and needles in legs), meningitis, which occurs in about one out of 25 people with polio, and paralysis, which occurs in about one out of 200 people.
Paralysis is the most severe symptom associated with polio, because it can lead to permanent disability and death. The CDC says, between two and 10 out of 100 people who have paralysis from polio die, because the virus affects the muscles that help them breathe.
Even children who seem to fully recover can develop new muscle pain, weakness, or paralysis as adults, 15 to 40 years later. This is called post-polio syndrome.
How is polio spread?
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The polio virus lives in an infected person's throat and intestines. People carrying the poliovirus, including those without symptoms, can spread the highly contagious virus for weeks in their feces. In rare cases, viral transmission can occur via droplets from a sneeze or cough, the CDC said.
Most people come into contact with polio by picking up a tiny piece of infected poop and then touching the mouth. Exposure to the virus also occurs when children mouth toys or other objects contaminated with feces.
In unsanitary conditions, the virus can also spread via contaminated food and water.
An infected person may spread the virus to others immediately before and up to two weeks after symptoms appear.
People who don't have symptoms can still pass the virus to others and make them sick.
How do you prevent, treat the virus?
There is no cure for polio, only treatment to alleviate the symptoms. Vaccination is the only prevention.
There are two types of vaccine that can prevent polio:
- Inactivated poliovirus vaccine (IPV) given as an injection in the leg or arm, depending on the patient's age. Only IPV has been used in the United States since 2000.
- Oral poliovirus vaccine (OPV) is still used throughout much of the world, but it no longer licensed or available in the United States. Children receive doses of the vaccine by drops in the mouth.
Polio vaccine protects children by preparing their bodies to fight the poliovirus. Almost all children (99 children to 100 out of 100) who get all the recommended doses of the inactivated polio vaccine will be protected from polio, according to the CDC.
Who should get the polio vaccine?
Children in the U.S. should get inactivated polio vaccine (IPV) to protect against the virus. They should get four doses total, with one dose at each of the following ages: 2 months old, 4 months old, 6 through 18 months old and 4 through 6 years old.
Most adults do not need the polio vaccine because they were already vaccinated as children. But three groups of adults are at higher risk and should consider polio vaccination in the following situations:
- You are traveling to a country where the risk of getting polio is greater.
- You are working in a laboratory and handling specimens that might contain the virus.
- You are a healthcare worker treating patients who could have polio or have close contact with a person who could be infected with poliovirus.
Adults in these three groups who have never been vaccinated against polio should get three doses of the vaccine. They should get the first dose at any time, the second dose one to two months later, and the third dose six to 12 months after the second.
Who shouldn't get the vaccine?
- Any person getting the vaccine who has had any severe or life-threatening allergic reactions after a dose of the vaccine, or have a severe allergy to any part of the vaccine, may be advised not to get vaccinated. Ask your health care provider if you want information about vaccine components.
- If the person getting the vaccine has a mild illness, such as a cold, you can probably get the vaccine today. However, if you are moderately or severely ill, you should probably wait until you recover. Your doctor can advise you.
The Associated Press and CNNwire contributed to this report
Below you can find links to helpful resources on polio
WHAT IS POLIO
WHAT EVERYONE SHOULD KNOW
WHO NEEDS TO GET VACCINATED
POLIO: FOR TRAVELERS
POST-POLIO SYNDROME
INFO FOR HEALTHCARE PROVIDERS
THE WHO: POLIO OVERVIEW
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