OVERVIEW 

During infancy, the child is at risk of a wide variety of infections. These are normally known as the six killer diseases in West Africa. It is normally mandatory that every child is immunized against these infections.

However, most parents are negligent of such duties and leave the child at risk of these infections. One of these is an infection, currently without a cure and is known to cause significant disability called Poliomyelitis. Most of us have heard of polio through social media and health forums but do we know it in detail?

WHAT IS POLIOMYELITIS?

Poliomyelitis is an acute infection caused by the poliovirus. It affects the nerves and can cause permanent muscle weakness, paralysis, and other significant symptoms.

The poliovirus has 3 serotypes. Type 1 is the most common cause of paralysis and also a common cause of epidemics. Infection is highly transmissible via direct contact. Humans are the only natural host of the virus.

The infection usually begins in the intestine. It then may spread to the parts of the brain and spinal cord that control the muscles.

TRANSMISSION

The infection is spread by ingesting food or water contaminated with stool from an infected person or by touching a contaminated surface, and then touching the mouth. Sometimes the virus is spread through saliva from an infected person or droplets expelled when an infected person sneezes or coughs.

People become infected when they inhale airborne droplets or touch something contaminated with the infected saliva or droplets.

EPIDEMIOLOGY

Acute poliomyelitis has a worldwide distribution, with a peak season from July to September and a concentration in tropical areas of the Northern hemisphere. It continues to occur epidemically in non-immunized populations, especially in developing regions.

Poor sanitation and crowding are two additional factors associated with the dissemination of the disease. 21 previously polio-free countries experienced a resurgence of wild-type polio from 2002 to 2005.

In 2013, it was reported that Syria, after having polio eradicated for 15 years, had a return of the disease. 13 cases were reported from the Deir Al Zour province, caused by the wild poliovirus type I.
Insurgent areas in Nigeria have had the transmission of the virus undetected.

This is due to access limitations for poliovirus surveillance as stated by the Center for Disease Control and Prevention in 2018.
Currently, cases due to wild poliovirus have decreased over 99% since 1988, from an estimated 350,000 cases then, to 33 reported cases in 2018 according to the World Health Organization.

PATHOPHYSIOLOGY

The poliovirus enters the host via the fecal-oral or respiratory route, then enters the lymphoid tissues of the intestines. A primary viremia (virus present in the blood) follows, with the spread of the virus to the reticuloendothelial system. Infection may be contained at this point, or the virus may further multiply and cause several days of secondary viremia.

This leads to the development of symptoms and antibodies. In paralytic infections, the virus enters the nervous system; whether this happens via secondary viremia or via migration up peripheral nerves remains unclear. Significant damage occurs only in the spinal cord and brain, particularly in the nerves controlling motor and autonomic function. Inflammation worsens the damage produced by the primary viral invasion.

The poliovirus is present in the throat and feces during incubation and, after the onset of symptoms, persists 1 to 2 weeks in the throat and more than 3 to 6 weeks in feces.

SIGNS AND SYMPTOMS

Most infections, about 70-75%, cause no symptoms. However, the symptomatic disease is classified as:

• Abortive poliomyelitis: The most symptomatic form of infection, present particularly in young children. Normally involves 1 to 3 days duration of slight fever, malaise, headache, sore throat, and vomiting, which develop 3 to 5 days after exposure. There are no neurologic symptoms or signs, and physical examination is unremarkable except for the presence of fever.

• Nonparalytic poliomyelitis: This involves a serious form of polio, typically presenting with a stiff neck and/or back and headache (aseptic meningitis). This occurs several days after the flu-like symptoms of abortive poliomyelitis. The symptoms last 2 to 10 days. Paralysis does not occur.

• Paralytic poliomyelitis: This involves paralysis in addition to aseptic meningitis. The symptoms usually appear 7 to 21 days after infection, involving fever, severe headache, a stiff neck and back, and deep muscle pain.

Sometimes, areas of the skin develop odd sensations, such as a feeling of pins and needles pricking the skin or unusual sensitivity to pain. Depending on the parts of the brain and spinal cord affected, the disease may progress no further, or weakness and paralysis may develop in certain muscles.

Typically, paralysis is common in the arms and legs, making them limp and unable to contract (flaccid paralysis).
There may be difficulty in swallowing and breathing due to paralysis of the chest muscles and muscles of the gastrointestinal tract.

DIAGNOSIS

A health practitioner can diagnose poliomyelitis through the following laboratory investigations:

1. Tests on a sample of stool or secretions from the throat.
2. Blood tests
3. A spinal tap of cerebrospinal fluid (CSF)

Poliomyelitis can be diagnosed by health practitioners through the signs and symptoms of the infection.

1. Abortive poliomyelitis resembles other viral infections and is typically not diagnosed unless it occurs during a polio epidemic.
2. Nonparalytic poliomyelitis is suspected in people who have flu-like symptoms and stiff neck and/or back.
3. Paralytic poliomyelitis is suspected in people who have muscle or limb paralysis or weakness.

TREATMENT

As stated earlier, polio has no cure, therefore supportive treatment is the only available option for the patient. This includes the following:
1. Adequate bed rest
2. Drugs to relieve pain and lower fever

Currently, the antiviral drugs available do not affect the course of the disease. A ventilator ( a machine which helps get air in and out of the lungs) may be needed if the muscles used in breathing are weakened. The need of the ventilator may only be temporary.

PREVENTION

Though polio has no cure, it can be prevented. The polio vaccine is available and included among the routine childhood immunizations. The vaccine is effective in more than 95% of children.

Currently, two types of the vaccine are available worldwide:

1. An inactivated poliovirus vaccine (Salk vaccine) given by injection.
2. A live oral poliovirus vaccine (Sabin vaccine) taken by mouth.

The live oral vaccine provides better immunity in a population but can mutate and cause 1 case of polio for every 2.4 million doses given. Currently, the oral vaccine is not given in the United States but is given in most developing countries.

Widespread immunization can stop the spread of both types of polio outbreaks, and travelers to certain countries may need to show proof of adequate vaccination.

KEY POINTS

• Routine vaccination can prevent polio infection.
• There is no cure for polio, but it can be prevented.
• Polio affects children more than adults.
• Some children recover completely, whereas others have permanent weakness.
• Symptoms of poliomyelitis include fever, headache, stiff neck and back, deep muscle pain and sometimes weakness or paralysis.