Polio, also known as poliomyelitis, is a highly infectious viral disease that can cause paralysis. Most of the world's countries are free from polio, although small numbers of cases are still reported in Afghanistan and Pakistan. In particular, it is found in areas where water treatment and sanitation facilities are not properly maintained or are nonexistent.
Although children under 5 years of age make up more than half of all cases, polio can affect people of any age.
The World Health Organization is at the heart of a plan to help make the world free from the disease. Since there is no animal infection or reservoir of the virus, the complete removal of the disease from the human population through vaccination is possible. The number of polio-endemic countries in 1988 was over 125; in early 2015, this number had been reduced to just 2, and the number of reported cases decreased from an estimated 350,000 in 1988 to 33 in 2018.
Polio is caused by infection with the poliovirus. This virus is highly contagious, and is passed on through food and water contaminated with the stool (feces) of infected people. It can take 4 to 21 days before symptoms appear, and an infected person can pass the virus on to other people even before symptoms appear.
Infection with polio happens when the virus enters the body through the mouth, multiplies in the throat and intestine, and spreads through the blood to the central nervous system. There, the virus attacks nerve cells, which can lead to paralysis.
Symptoms and Complications
Polio is a serious condition that causes paralysis. However, this occurs in less than 1% of those infected (paralytic polio). Most people do not become sick at all. In a small number of cases, the disease causes flu-like symptoms but does not lead paralysis (non-paralytic polio).
Non-paralytic polio causes symptoms that mimic the flu. A person may experience a sore throat, fatigue, nausea, diarrhea, a fever, or vomiting. Most cases of non-paralytic polio clear up in a number of days, but some people go on to develop meningitis, a condition in which the lining of the brain is infected. Meningitis can be fatal if it is not treated quickly.
When a person develops paralytic polio, the symptoms are more serious. As the virus spreads through the nerves, it destroys nerves that control muscles. The infection may be fatal if the brain and respiratory organs become affected.
Making the Diagnosis
The doctor may suspect a person has polio if they show symptoms of the condition, such as stiff neck and back, trouble breathing, or nausea. This is particularly true for people who come from a high-risk area or those who have not been vaccinated against polio.
To confirm the diagnosis, the doctor will take samples from the throat, stool, and the fluid surrounding the brain and spinal cord.
Treatment and Prevention
Because there is no cure for polio, supportive therapy is the main treatment. Improving a person's chance of recovery is the main goal of treatment. This type of treatment helps minimize discomfort and prevent complications while the person recovers. Supportive treatment may include medications for polio symptoms, ventilators to help the person breathe, exercise, and a balanced diet.
Polio is not a treatable disease, yet it is almost completely preventable. Vaccination with the polio vaccine provides the most effective form of prevention. Childhood immunization programs protect Canadians from infection by the poliovirus.
Health Canada recommends you check with your family doctor before traveling overseas as you may be going to a high-risk area. Getting the vaccination before you leave may protect you while traveling, especially if you have never been vaccinated against polio.