What Is Polio?
Polio is the common name for poliomyelitis. In the past for a brief period, polio was called infantile paralysis, although it did not affect only the young. It is a crippling and potentially deadly infectious disease. It is caused by polio-virus. The virus spreads from person to person and can invade an infected person’s brain and spinal cord, causing paralysis.
It is likely that polio has affected humans for thousands of years. An Egyptian carving from around 1400 BCE shows a young man with a leg abnormality similar to one caused by polio. Poliomyelitis circulated in populations at low levels and seemed to be a relatively uncommon disease for most of the 1800s.
Polio reached epidemic magnitudes in the early 1900s in countries with relatively high standards of living, at a time when other infectious diseases such as diphtheria, typhoid, and tuberculosis were declining. Many scientists proposed that advances in hygiene led to an increased incidence of polio. The theory is that in the past, children were exposed to polio, mostly through contaminated water, at a very young age. Infants’ immune systems, supported by maternal antibodies still circulating in the blood, could swiftly defeat polio-virus and then develop lifelong immunity to it. However, improved sanitary conditions meant that exposure to polio was delayed until later in life, on average, when a child had lost maternal protection and was also more vulnerable to the most severe form of the disease.
Polio is caused by the polio-virus. These viruses spread through contact between people, by nasal and oral secretions, and by contact with contaminated feces. Polio-virus enters the body through the mouth, multiplying along the way to the digestive tract, where it further multiplies. In about 98% of cases, polio is a mild illness, with no symptoms or with viral-like symptoms. In paralytic polio, the virus leaves the digestive tract, enters the bloodstream, and then attacks nerve cells. Less than 1%-2% of people who contract polio become paralyzed. In severe cases, the throat and chest may be paralyzed. Death may result if the patient does not receive artificial breathing support.
Most people who get infected with polio-virus (about 72 %) will not have any visible symptoms.
About 1 out of 4 people with polio-virus infection will have flu-like symptoms that may include—
• Sore throat
• Stomach pain
These symptoms usually last for 2 to 5 days then go away on their own. A smaller proportion of people with polio-virus infection will develop some of the other more serious symptoms that affect the brain and spinal cord:
• Parenthesis (feeling of pins and needles in the legs)
• Meningitis (infection of the covering of the spinal cord and/or brain)
• Paralysis or weakness in the arms, legs, or both
• Paralysis is the most severe symptom associated with polio because it can lead to permanent disability and death. Between 2 and 10 out of 100 people who have paralysis from polio-virus infection die because the virus affects the muscles that help them breathe.
Transmission of Polio
Polio-virus only infects humans. It is highly contagious and spreads through person-to-person contact. The polio virus lives in an infected person’s throat and intestines. It enters the body through the mouth and spreads through contact with the feces (poop) of an infected person and, though less common, through droplets from a sneeze or cough. An infected person may spread the virus to other people immediately before and almost 1 to 2 weeks after symptoms appear. The virus can live in an infected person’s feces for many weeks. It can contaminate food and water in unsanitary conditions. People who don’t have symptoms can still pass the virus to others that can lead to polio disease.
Polio vaccine protects children by preparing their bodies to fight the poliovirus. Almost all children who get all the recommended doses of vaccine will be protected from polio. Because of widespread vaccination, polio was eliminated from the Western Hemisphere in 1994. In 2016, it continues to circulate in just Afghanistan and Pakistan, with occasional spread to neighboring countries. Vigorous vaccination programs are being conducted to eliminate these last pockets. Polio vaccination is still recommended worldwide because of the risk of imported cases.
The surge of New Polio Cases in Pakistan and Afghanistan
False rumors that children are fainting or dying have led parents to turn away vaccinators, threatening the campaign to eradicate the disease. The global drive to eliminate tetanus, which has gone on for 31 years and consumed over $16 billion, has been set back again by a surge of new cases in Pakistan and Afghanistan. False rumors spread on social media saying the vaccine had triggered fainting spells — or even that it had killed dozens of children — and many families locked their doors to vaccinators or hid their children.
When to see a doctor
Check with your doctor for polio vaccination recommendations before traveling to a part of the world where polio still occurs naturally or where oral polio vaccine (OPV) is used, such as Central and South America, Africa and Asia.