Filed under: Infectious Diseases
Polio is a contagious
viral illness that in its most severe form causes paralysis, difficulty
breathing and sometimes death.
In the U.S., the last
case of wild polio — polio caused naturally, not by a vaccine containing live
virus — occurred in 1979. Today, despite a concerted global eradication
campaign, wild poliovirus continues to affect children and adults in
Afghanistan, India, Nigeria and Pakistan.
The Centers for
Disease Control and Prevention (CDC) advises taking precautions to protect
against polio if you're traveling anywhere there's a risk of polio. If you're a
previously vaccinated adult who plans to travel to an area where polio is
occurring, you should receive a booster dose of inactivated poliovirus.
Immunity following a booster dose lasts a lifetime.
Although polio can
cause paralysis and death, the vast majority of people who are infected with
the poliovirus don't become sick and are never aware they've been infected with
polio.
Nonparalytic polio
. Some people who develop symptoms from the
poliovirus contract nonparalytic polio — a type of polio that doesn't lead to
paralysis (abortive poliomyelitis). This usually causes the same mild, flu-like
signs and symptoms typical of other viral illnesses.
Signs and symptoms,
which generally last two to 10 days, include:
•
Fever
•
Sore throat
•
Headache
•
Vomiting
•
Fatigue
•
Back pain or stiffness
•
Neck pain or stiffness
•
Pain or stiffness in
the arms or legs
•
Muscle spasms or
tenderness
•
Meningitis
Paralytic polio
. Fewer than 1 percent of people infected with
poliovirus develop paralytic polio, the most serious form of the disease.
Initial signs and symptoms of paralytic polio, such as fever and headache,
often mimic those of nonparalytic polio. Between one and 10 days later however,
signs and symptoms specific to paralytic polio appear, including:
•
Loss of reflexes
•
Severe muscle aches or
spasms
•
Loose and floppy limbs
(acute flaccid paralysis), often worse on one side of the body
The onset of paralysis
may be sudden.
Classifications of
paralytic polio
Paralytic polio has
historically been divided into several types, depending primarily on which part
of the body is affected. These classifications aren't rigid, and overlap may
occur among the different forms.
•
Spinal polio. This most common form of paralytic polio attacks
certain nerve cells (motor neurons) in your spinal cord and may cause paralysis
of the muscles that control breathing and those in your arms and legs.
Sometimes the neurons are only damaged, in which case you may recover some
degree of muscle function. But if the neurons are completely destroyed, the
paralysis is irreversible, although you still retain your sense of feeling,
unlike after many spinal cord injuries.
•
Bulbar polio. In this severe type of polio, the virus affects
the motor neurons in your brainstem, where the centers of the cranial nerves
are located. These nerves are involved in your ability to see, hear, smell,
taste and swallow. They also affect the movement of muscles in your face and
send signals to your heart, intestines and lungs. Bulbar polio can interfere
with any of these functions but is especially likely to affect your ability to
breathe, speak and swallow and can be fatal without respiratory support.
•
Bulbospinal polio. A combination of both bulbar and spinal paralytic
polio, this form can lead to paralysis of your arms and legs and may also
affect breathing, swallowing and heart function.
Post-polio syndrome.
Affecting some people who have recovered from
polio, post-polio syndrome is a cluster of disabling signs and symptoms that
appears decades — an average of 30 to 40 years — after the initial illness.
Common signs and symptoms include:
•
Progressive muscle or
joint weakness and pain
•
General fatigue and
exhaustion after minimal activity
•
Muscle atrophy
•
Breathing or swallowing
problems
•
Sleep-related
breathing disorders, such as sleep apnea
•
Decreased tolerance of
cold temperatures
When to see a doctor
. Be sure to check with your doctor for polio
vaccination recommendations before traveling to a part of the world where polio
may still occur naturally or where oral polio vaccine (OPV) is still used, such
as Central and South America, Africa and Asia. In countries that use the OPV —
vaccine made with live, but weakened (attenuated) polio virus — the risk of
paralytic polio to travelers is extremely low, but not zero.
Additionally, call
your doctor if:
•
Your child hasn't
completed the series of polio vaccinations
•
Your child experiences
an allergic reaction after receiving polio vaccine
•
Your child has
problems other than a mild redness or soreness at the vaccine injection site
•
You have questions
about adult vaccination or other concerns about polio immunization
•
You had polio years
ago and are now experiencing unexplained weakness and fatigue
The poliovirus resides
only in humans and enters the environment in the feces of someone who's
infected. Poliovirus spreads primarily through the fecal-oral route, especially
in areas where sanitation is inadequate.
Poliovirus can be
transmitted through contaminated water and food or through direct contact with
someone infected with the virus. Polio is so contagious that anyone living with
a recently infected person is likely to become infected too. Although people
carrying the poliovirus are most contagious seven to 10 days before and after
signs and symptoms appear, they can spread the virus for weeks in their feces.
You're at greatest
risk of polio if you haven't been immunized against the disease. In areas with
poor sanitation and sporadic or nonexistent immunization programs, the most
vulnerable members of the population — pregnant women, the very young and those
with weakened immune systems — are especially susceptible to poliovirus.
These factors also
increase your risk if you haven't been vaccinated:
•
Travel to an area
where polio is common or that has recently experienced an outbreak
•
Living with or caring
for someone who may be shedding poliovirus
•
Handling laboratory
specimens that contain live poliovirus
•
A compromised immune
system, such as occurs with HIV infection
•
Having had your
tonsils removed (tonsillectomy)
•
Extreme stress or
strenuous physical activity after being exposed to poliovirus, both of which
can depress your immune system
Paralytic polio can
lead to temporary or permanent muscle paralysis, disability, and deformities of
the hips, ankles and feet. Although many deformities can be corrected with
surgery and physical therapy, these treatments may not be options in developing
nations where polio is still endemic. As a result, children who survive polio
may spend their lives with severe disabilities.
Doctors often
recognize polio by symptoms such as neck and back stiffness, abnormal reflexes,
and difficulty swallowing and breathing. To confirm the diagnosis, a sample of
throat secretions, stool or cerebrospinal fluid — a colorless fluid that
surrounds your brain and spinal cord — is checked for the presence of
poliovirus.
Because no cure for
polio exists, the focus is on increasing comfort, speeding recovery and
preventing complications. Supportive treatments include:
•
Bed rest
•
Antibiotics for
secondary infections (none for poliovirus)
•
Analgesics for pain
•
Portable ventilators
to assist breathing
•
Moderate exercise
(physiotherapy) to prevent deformity and loss of muscle function
•
A nutritious diet
