Polio is a contagious viral illness that in its most severe form causes paralysis, difficulty breathing and sometimes death.
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
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. Some people who develop symptoms from the poliovirus contract nonparalytic polio — a type of polio that doesn’t lead to paralysis. 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:
- Sore throat
- Back pain or stiffness
- Neck pain or stiffness
- Pain or stiffness in the arms or legs
- Muscle spasms or tenderness
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.
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
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.