Polio

Polio is a sickness.

It comes from tiny germs. These germs spread through dirty food or water. Most people do not feel very sick. They might just have a fever.

Some people get very weak. Their muscles may stop working. This can happen in the legs. A shot can keep you safe.

These shots help stop the sickness. This keeps children healthy and strong.

Polio is a sickness caused by a tiny germ. We call this germ the poliovirus.

This virus only lives in humans. It is very easy to spread. People can get it from dirty food or water.

Most people do not feel very sick. They might have a sore throat or a fever. These small signs usually go away in two weeks.

Sometimes the virus travels to the central nervous system. This is the part of the body that controls movement. The virus can attack motor neurons. These are cells that tell your muscles to move.

If these cells are hurt, the muscles become weak. This can lead to paralysis. This means a person cannot move their body parts. This often happens in the legs.

Doctors can prevent polio with a vaccine. A vaccine is a way to teach the body to fight germs. There are two main kinds of vaccines. One is a shot. The other is medicine you swallow.

These vaccines have helped stop the virus. In 1988, there were 350,000 cases. In 2022, there were only 30 cases.

Polio is a serious disease caused by the poliovirus.

This virus only lives in humans. It is highly infectious, which means it spreads very easily between people. Most people who get it do not even know. About 75% of cases have no symptoms at all. Other people might feel a little sick with a fever or sore throat. These small illnesses usually pass within one or two weeks.

The virus enters the body through the mouth. It often spreads through food or water that is not clean. Once inside, the virus settles in the throat and the intestines. It then enters the bloodstream to travel through the body. This is called viremia. In some rare cases, the virus moves into the central nervous system. It can attack motor neurons, which are the cells that tell muscles to move.

When the virus attacks these nerve cells, it can cause paralysis. This means the muscles become weak and floppy. This often happens in the legs. In very serious cases, it can affect the muscles used for breathing. This can lead to death. Some people may even face post-polio syndrome years later. This causes muscle weakness to return slowly.

People have known about polio for thousands of years. Ancient art even shows the disease. An English doctor named Michael Underwood recognized it as a specific condition in 1789. Later, an Austrian scientist named Karl Landsteiner identified the actual virus in 1909.

Big outbreaks happened in Europe and the United States during the late 1800s. By the 20th century, it was a major worry for parents of young children.

Today, vaccines are the best way to stay safe. There is an injected vaccine and an oral vaccine.

These vaccines have worked incredibly well. In 1988, there were about 350,000 cases of polio. By 2022, there were only 30 confirmed cases left. Now, the virus is only found in two countries, Pakistan and Afghanistan.

This shows how much medicine can change the world.

Poliomyelitis, often called polio, is a highly infectious disease caused by the poliovirus.

This virus belongs to a group called enteroviruses, which are known to colonize the human gastrointestinal tract. While the disease can be quite severe, it is important to note that it occurs naturally only in humans. The term itself comes from Ancient Greek, meaning "grey matter inflammation," referring to the part of the spinal cord the virus often affects.

Understanding how this virus moves through the body and how we fight it is a major part of modern medicine.

The virus enters the body through the mouth, typically via the fecal–oral route. This happens when a person ingests food or water contaminated by human feces, often due to poor hygiene. It can also spread through the oral–oral route. Once inside, the virus targets the oropharynx and the intestinal mucosa. It enters cells by binding to a specific receptor called CD155. After entering, the virus hijacks the host cell's machinery to replicate itself.

This replication occurs within the gastrointestinal cells for about one week before spreading to the lymph nodes and the bloodstream. This stage, where the virus is in the blood, is known as viremia.

Most people who catch the virus do not realize they are sick. Approximately 75% of cases are asymptomatic, meaning they show no symptoms at all. About 25% of people experience a minor illness, sometimes called abortive poliomyelitis. These symptoms include a sore throat, fever, and general discomfort, but usually pass within one or two weeks. However, in about 1% of cases, the virus migrates from the gut into the central nervous system (CNS). This can cause nonparalytic aseptic meningitis, which involves inflammation of the membranes surrounding the brain and spinal cord. Patients might feel headaches, neck stiffness, or abdominal pain during this time.

In a small number of cases, the infection progresses to paralytic poliomyelitis. This occurs when the virus destroys motor neurons, the nerve cells that control muscle movement. This leads to acute flaccid paralysis, where muscles become weak, floppy, and lose control.

Depending on where the damage occurs in the CNS, doctors classify the paralysis into three types. Spinal polio affects the spinal cord, while bulbar polio affects the brain stem. Bulbospinal polio involves both regions.

If the paralysis affects the muscles used for breathing, it can be fatal. Between 2% and 10% of those with paralytic polio may die from this cause.

Humans have lived with polio for thousands of years, with ancient art even depicting the disease.

The English physician Michael Underwood first recognized it as a distinct medical condition in 1789. Later, the Austrian immunologist Karl Landsteiner identified the actual poliovirus in 1909. By the late 19th century, major outbreaks began appearing in Europe and the United States. During the 20th century, polio became one of the most feared childhood diseases globally. This changed rapidly after the introduction of vaccines in the 1950s.

Vaccines are the most effective way to prevent the disease. There are two main types used to create immunity. The injected polio vaccine (IPV) uses inactivated, or killed, poliovirus. The oral polio vaccine (OPV) uses attenuated, or weakened, live virus.

While OPV is effective, in rare instances, the weakened virus can mutate back into a virulent form in areas with low vaccine coverage. This is known as circulating vaccine-derived poliovirus (cVDPV). To address this, a more genetically stable version called nOPV2 was granted full licensure by the World Health Organization in December 2023.

The impact of vaccination has been massive. In 1988, there were an estimated 350,000 cases of wild poliovirus worldwide. By 2022, that number had dropped to only 30 confirmed cases.

Today, wild poliovirus remains endemic in only two countries: Pakistan and Afghanistan. This progress shows how global health efforts can nearly eliminate a dangerous pathogen. Even as we fight the virus, some survivors deal with post-polio syndrome, which brings back muscle weakness many years after the initial recovery.