What is poliomyelitis? Symptoms and prevention

What is poliomyelitis

Poliomyelitis is a very contagious disease caused by a virus, the poliovirus, which invades the nervous system and which can cause irreversible paralysis within a few hours. Since the 1960s this disease can be prevented with effective vaccines. A global program to eradicate the disease through vaccination has been launched under WHO supervision.

Symptoms of Poliomyelitis

The Poliomyelitis disease first manifests with flu-like symptoms (fever, fatigue, headache) which may be accompanied by vomiting, stiff neck and pain in the limbs. Irreversible paralysis (usually of the legs) occurs in about one in 200 infected people. Without palliative measures, between 5 and 10% of paralyzed patients die from asphyxiation due to paralysis of the muscles providing ventilation. In patients who survive, residual paralysis can be observed causing disabilities with varying degrees of damage. These range from minor paralyzes leaving complete independence to extremely disabling paralyzes which may require lifelong breathing assistance.

Some former patients develop, several decades after acute polio, a “post-polio” syndrome which is characterized by new deficits progressing slowly. The exact causes of the prevalence of this disease are not currently well defined. It could be due to the persistence of the virus in some patients.

Causes of Poliomyelitis

The polio virus is a member of the picornavirus family and belongs to the genus Enterovirus. There are three serotypes of poliovirus (1, 2 and 3), each capable of inducing disease.

Poliomyelitis is caused by infection with the poliovirus. This virus is highly contagious and is spread through food and water contaminated with the feces (feces) of infected people. It can take 4 to 21 days for symptoms to appear and one infected person can pass the virus to another, even before symptoms appear.

Poliomyelitis infection occurs 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. At this point, the virus attacks nerve cells, which can lead to paralysis.


Causes of Poliomyelitis

Doctors may think a person has polio if they have symptoms of the condition, such as stiff neck and back, difficulty breathing, or nausea. This is especially true for people who come from a high risk area or for those who have not been vaccinated against polio.

In order to be able to confirm the diagnosis, the doctor will take samples of the throat, feces and fluid surrounding the brain as well as the spinal cord.

Poliovirus Transmission 

The polio virus multiplies in the pharyngeal lining and in the small intestine  and can be found in the throat and stool. Its transmission is exclusively human-to-human and takes place mainly by the faecal-oral route, in particular through contaminated water, aerosols or food contaminated by the stool. Infected people can spread the infection as long as the virus persists in the throat (one week) and in the feces (3 to 6 weeks or even longer).

The virus enters the body through the mouth and, passing through the lining of the throat or the intestinal lining, multiplies in the cervical or mesenteric lymph nodes (of the small intestine). In  1 to 2% of infected individuals, the virus affects, probably through the bloodstream,  the motor neurons of the anterior horn of the spinal cord or other motor regions of the central nervous system, the destruction of which is responsible for forms of flaccid paralysis. It is generally accepted that the death of motor neurons is a direct consequence of viral replication.

Prevention of Poliomyelitis

Since the transmission of polioviruses takes place mainly by the  faecal-oral route , the main preventive measures relate to the  development of hygiene . As there is no treatment for the disease, the only preventive medical action is vaccination, which, carried out several times, protects the child.

Before the vaccine era, polio was one of the most terrible plagues of childhood. In the 1980s, polio still affected several hundred thousand children around the world every year. To defeat the disease, in 1988 WHO launched the Global Polio Eradication Initiative. This is based on two pillars: surveillance, which aims to detect the circulation of poliovirus as early as possible, and vaccination of all children in the world.

Types of vaccines against the Poliovirus

vaccines against the Poliovirus

Injectable Polio Vaccine (IPV)

It was developed by Jonas Salk in the 1950s and contains all three inactivated virus serotypes and induces protection due to good general immunity. As this vaccine requires several injections and regular boosters, it must be used under controlled aseptic conditions. It is completely safe, but its production cost and the logistics associated with its use have long limited its distribution to certain developed countries such as France. However, its use is constantly expanding.

Oral Polio Vaccine (OPV)

The Oral Polio Vaccine (OPV) was developed by Albert Sabin, also in the 1950s. OPV contains live polioviruses but attenuated by mutations: the strains contained in the vaccine (one strain of each of the three serotypes) infect people. vaccinated but are much less likely to infect the central nervous system than unattenuated strains. This vaccine has many advantages, which explains why it has until now been the preferred tool of the eradication program: it is easy to administer because it does not require injection, it quickly confers good general immunity and local immunity in the intestine, consequently reducing the transmission of wild poliovirus (which IPV does much less effectively); OPV is also very affordable.

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