Polio (also called poliomyelitis) is a contagious, historically
devastating disease that was virtually eliminated from the Western hemisphere in the
second half of the 20th century. Although polio has been around since ancient
times, its most extensive outbreak occurred in the first half of the 1900s until the
was introduced in 1955.
At the height of the polio epidemic in 1952, nearly 60,000 cases with more than
3,000 deaths were reported in the United States alone. However, with widespread vaccination,
wild-type polio, or polio occurring through natural infection, was
eliminated from the United States by 1979 and the Western hemisphere by 1991.
Signs and Symptoms
Polio is a viral illness that, in about 95% of cases, actually produces no symptoms
at all (called asymptomatic polio). In the 4% to 8% of cases in which
there are symptoms (called symptomatic polio), the illness appears
in three forms:
a mild form called abortive polio (most people with this type
may not even suspect they have it because their sickness is limited to mild flu-like
symptoms such as mild upper respiratory infection, diarrhea,
throat, and a general feeling of being ill)
a more serious form associated with aseptic meningitis
called nonparalytic polio (1%-5% show neurological symptoms such
as sensitivity to light and neck stiffness)
a severe, debilitating form called paralytic polio (this occurs
in 0.1%-2% of cases)
People who have abortive polio or nonparalytic polio usually make a full recovery.
However, paralytic polio, as its name implies, causes muscle paralysis — and
can even result in death.
In paralytic polio, the virus leaves the intestinal tract and enters the bloodstream,
attacking the nerves (in abortive or asymptomatic polio, the virus usually doesn't
get past the intestinal tract). The virus may affect the nerves governing the muscles
in the limbs and the muscles necessary for breathing, causing respiratory difficulty
and paralysis of the arms and legs.
Polio is transmitted primarily through the ingestion of material contaminated with
the virus found in stool (poop). Not washing
hands after using the bathroom and drinking contaminated water were common culprits
in the transmission of the disease.
In the United States, it's currently recommended that children have four doses
of inactivated polio vaccination (IPV) between the ages of 2 months and 6 years.
By 1964, the oral polio vaccine (OPV) had become the recommended vaccine. OPV allowed
large populations to be immunized because it was easy to administer, and it provided
"contact" immunization, which means that an unimmunized person who came in contact
with a recently immunized child might become immune, too.
The problem with OPV was that, in very rare cases, paralytic polio could develop
either in immunized children or in those who came in contact with them. Since 1979
(when wild polio was eliminated in the United States), the approximately 10 cases
per year of polio seen in this country were traced to OPV.
IPV is a vaccine that stimulates the immune system of the body (through production
of antibodies) to fight the virus if it comes in contact with it. IPV cannot
In an effort to eradicate all polio, including those cases associated with the
vaccine, the Centers for Disease Control and Prevention (CDC) decided to make IPV
the only vaccine given in the United States. Currently, the CDC and American Academy
of Pediatrics (AAP) recommend three spaced doses of IPV given before the age of 18
months, and an IPV booster given between the ages of 4 to 6, when children are entering
If you're planning to travel outside the United States, particularly to Africa
and Asia (where polio still exists), be sure that you and your kids have received
a complete set of polio vaccinations.
Although the acute illness usually lasts less than 2 weeks, damage to the nerves
could last a lifetime. In the past, some patients with polio never regained full use
of their limbs, which would appear withered. Those who did fully recover might go
on to develop post-polio syndrome (PPS) as many as 30 to 40 years after contracting
polio. In PPS, the damage done to the nerves during the disease causes an acceleration
of the normal, gradual weakness due to aging.
During the height of the polio epidemic, the standard treatment involved placing
a patient with paralysis of the breathing muscles in an "iron lung" — a large
machine that actually pushed and pulled the chest muscles to make them work. The damaged
limbs were often kept immobilized because of the confinement of the iron lung. In
countries where polio is still a concern, ventilators and some iron lungs are still
Historically, home treatment for paralytic polio and abortive polio with neurological
symptoms wasn't sufficient. However, asymptomatic and mild cases of abortive polio
with no neurological symptoms were usually treated like the flu, with plenty of fluids
and bed rest.
The Future of Polio
Health groups are working toward wiping out polio throughout the world,
and much progress has been made. But several countries still have polio circulating,
which means that the virus could occur in others. If the polio virus reaches
a country where not enough people have been immunized, it could spread from person
to person, as has happened in some countries in Africa and Asia. So until it has been
eliminated worldwide, it's important to continue vaccinating kids against polio.