Generality

Polio, or polio, is an acute and extremely contagious viral disease, which can affect the nerves of the central nervous system and cause temporary or permanent forms of paralysis .

Poliomyelitis is caused by an enterovirus called poliovirus, whose transmission among humans occurs mainly through the fecal-oral route.

For patients with poliomyelitis, involvement of the central nervous system can be fatal; fortunately, however, this phenomenon is very rare (it affects 6% of cases), while the mild (or minor) form of the disease, in which the poliovirus simply invades the intestine, is much more common.

Unfortunately, there is still no specific cure for polio; patients must therefore wait for the disease to progress, relying solely on symptomatic treatments planned on the basis of the severity of the infection.

The lack of a specific cure necessarily gives extreme relevance to prevention. Today, to prevent polio, vaccination is the most effective means of all.

What is polio?

Polio, or simply polio, is an extremely contagious and acute infectious viral disease, which can invade and damage the nerves of the central nervous system, and induce partial or total paralysis of the muscles of the body.

Polio is a potentially deadly condition.

Epidemiology

Today, polio is very rare, especially in industrialized countries, but at one time, before the advent of the first polio vaccine (1955), it was a viral infection widespread in all parts of the globe, especially among the youngest, and feared by the entire world population.

The current low incidence of poliomyelitis is the result of a program to eradicate this disease, started in 1988 and planned by WHO (World Health Organization), UNICEF and The Rotary Foundation. In recent years, the aforementioned program (consisting of mass vaccination) has been so efficient, which has led to a 99% reduction in polio cases.

According to the statistics, the number of global cases of polio has dropped from 350, 000 in 1988 to 483 in 2001 to reach 42 in 2016.

Currently, polio is still a real threat in countries like Afghanistan, Nigeria, Pakistan and India, where polio vaccination programs are not yet at the cutting edge.

Causes

As a viral infectious disease, poliomyelitis is the result of the action of a virus.

To be precise, the virus that causes polio is the so-called poliovirus .

The Poliovirus

Polyovirus is a viral agent belonging to the genus of human enteroviruses (NB: the same viruses that cause the intestinal virus) and to the family of picornaviruses .

Equipped with a capsid, the poliovirus has a single-stranded RNA genome, composed of about 7, 500 nucleotides.

In nature, there are three different serovars of poliovirus, called PV1, PV2 and PV3; to distinguish the various serotypes is the protein composition of the capsid.

When it invades a host, the poliovirus behaves exactly like all the other human enteroviruses: it settles in the intestine and, only once it reaches this site, it begins to replicate itself giving more or less evident manifestation of its presence.

As will be seen more fully in the chapter on symptoms, poliovirus can:

  • Just invade the intestinal tract and cause transient, asymptomatic or mildly symptomatic viremia

or

  • Spread, after the invasion of the intestine and the passage in the blood, to the central nervous system, affecting it more or less deeply and more or less permanently.

INCUBATION TIMES ...

The incubation period of the poliovirus (that is the time that must pass from the first exposure to the poliovirus to the appearance of the possible symptomatology) fluctuates between 6 and 20 days, even if it is good to specify that it can be even shorter (minimum 3 days) or further longer (maximum 35 days).

... AND OTHER CURIOSITIES

After infection, the poliovirus is present in the faeces and saliva of the infected individual, respectively, for several weeks and for a few days.

In temperate climate countries of the world, poliovirus is seasonal: in fact, the peak of infections is observed in summer and autumn. In geographical areas with tropical climate, however, poliovirus is active practically during all seasons of the year.

How polyovirus transmission occurs

The poliovirus is a microorganism whose transmission between human and human being can take place:

  • By the fecal-oral route ( fecal-oral transmission ). Doctors talk about fecal-oral transmission when, due to inadequate sanitary measures, a pathogen passes, in some way, from the digestive system of an infected person to the digestive system of a healthy person.

    For example, it is a case of fecal-oral transmission the circumstance in which an infected individual infects an uninfected individual, preparing food for the latter with hands not properly washed after defecation.

    The fecal-oral transmission represents, by far, the most common mode of transmission of poliovirus.

  • By contact with mucus, saliva or phlegm belonging to an infected individual and obviously containing the viral pathogen. It is an uncommon way of transmission, however possible.
  • For the simple contact between an infected person and an uninfected person . It is another way of transmission of the poliovirus that is decidedly uncommon.

Symptoms and complications

To learn more: Symptoms Polio

The neurological complications and potential deadly consequences of polio make the latter a very feared disease. It is good, however, to point out that, in most cases, polio is an asymptomatic or only slightly symptomatic condition, thus being similar to many other much less dangerous infections.

With regard to the possible course of polio and its aggressiveness, the most reliable medical investigations are fairly clear and report that:

  • In just over 70% of clinical cases, polio is an asymptomatic (ie symptomless) infection, which often takes its course without the knowledge of the infected person;
  • In about 24% of clinical cases, poliomyelitis is responsible, in a completely transient manner, for flu-like symptoms and other signs that accumulate many non-dangerous infections;
  • In about 5% of clinical cases, polio produces a form of aseptic meningitis, characterized by a very specific symptomatology;
  • Finally, in a small 1% of clinical cases, poliomyelitis is the cause of extremely serious neuronal lesions, which can cause the death of the patient due to the permanent paralysis of some important muscles of the human body.

According to reports from the medical-scientific community, and based on reports in medical texts, asymptomatic poliomyelitis and mildly asymptomatic poliomyelitis fall under the term polio minor or subclinical poliomyelitis ; the polio that causes aseptic meningitis is identified with the term non-paralytic poliomyelitis ; finally, polio that produces neurological damage and causes paralysis is called paralytic poliomyelitis .

Minor or subclinical poliomyelitis

When symptomatic, minor or subclinical poliomyelitis causes symptoms of slight clinical relevance, such as:

  • Fatigue;
  • Abdominal pain;
  • Nausea and vomit;
  • Diarrhea and / or constipation;
  • Mild fever (low-grade fever);
  • Irritability;
  • Sore throat;
  • General malaise.

When present, these symptoms generally remain for a week .

Non-paralytic poliomyelitis

Characterized by aseptic meningitis, non-paralytic poliomyelitis produces a very precise symptomatological picture, which includes:

  • Headache;
  • Pain and stiffness in the neck and back;
  • Strong abdominal pain;
  • Temperature;
  • Lethargy;
  • He retched;
  • Generalized muscle weakness;
  • Pain and stiffness in the arms and legs.

In these situations, the poliovirus has reached the central nervous system, without however deeply attacking it.

As a rule, the aforementioned symptomatology persists for 7-10 days, after which the recovery phase begins.

Paralytic poliomyelitis

Paralytic poliomyelitis manifests itself initially with symptoms similar to that of a normal flu; then, after about a week or two, it begins to produce symptoms such as:

  • Loss of reflexes;
  • Major muscle pains;
  • Inability to walk;
  • Temporary loss of skin sensitivity;
  • Muscle spasms;
  • Flaccid paralysis.

Flaccid paralysis is the most serious consequence of paralytic poliomyelitis, because it can jeopardize the ability to control the respiratory and swallowing muscles and, as a consequence, to increase exponentially the risk of respiratory insufficiency and suffocation from food phenomena.

It is no coincidence that among the people suffering from poliomyelitis, respiratory failure and suffocation are the main causes of death.

HOW PARALYTIC POLYOMIELITIS IS THE CAUSE OF FLACID PARALYSIS

When poliomyelitis produces paralysis of the body's muscles, it means that the poliovirus has reached the central nervous system and has invaded the brain and / or spinal cord motor neurons, causing a serious alteration of function or even destruction.

The invasion that poliovirus performs against motor neurons in the central nervous system does not always have the same consequences; the muscles that undergo paralysis, in fact, vary depending on the portion of brain or spinal cord affected by the polio virus.

Furthermore, paralysis can be temporary or permanent, depending on whether the viral invasion has caused temporary or permanent damage.

THE SUBTIPES OF PARALYTIC POLYOMIELITE

Experts recognize three subtypes (or forms) of paralytic poliomyelitis:

  • Spinal polio . It occurs when the poliovirus invades the spinal cord motor neurons.

    Effects: loss of control of trunk and limb muscles, and intercostal muscles.

    Other: subtype of the most common paralytic poliomyelitis.

  • Bulbar polio . It results when the poliovirus invades the motoneurons of the medulla oblongata (bulb) of the brainstem.

    Effects: weakening of the muscles under the control of the cranial nerves, encephalitis, difficulty breathing and swallowing, and language problems.

    Other: covers 2% of cases of paralytic poliomyelitis.

  • The bulbo-spinal polio (or respiratory poliomyelitis ). It appears when the poliovirus invades the motor neurons of the cervical portion of the spinal cord and the motoneurons of the medulla oblongata of the brainstem.

    Effects: severe swallowing problems and severe respiratory deficits (these are due to the involvement of the phrenic nerve, which controls the diaphragm).

    Other: covers 19% of cases of paralytic poliomyelitis.

Complications

In addition to the possible dramatic effects on breathing and swallowing capacities, paralytic poliomyelitis can lead to the onset of deformities and consequent disabilities in the hips, ankles and feet, as well as problems such as the paralytic ileus, urinary infections, the pulmonary heart, myocarditis, etc.

To all this we must add, then, the possibility that poliomyelitis (in whatever form it occurs) to trigger, years later, a condition known as post-polio syndrome .

POST-POLIO SYNDROME: WHAT IS IT?

With the term "post-polio syndrome", doctors understand that set of signs and symptoms, often highly debilitating, that afflict some people several years later (sometimes even 35 years later) the recovery from poliomyelitis.

This set of signs and symptoms includes:

  • Progressive myalgia (muscle pain) and arthralgia (joint pain), associated with weakness;
  • Sense of chronic fatigue;
  • Tendency to tire easily, even after minimal efforts;
  • Night apnea;
  • Muscular atrophy;
  • Difficulty sleeping;
  • Difficulty breathing and swallowing;
  • Poor cold tolerance;
  • Cognitive problems, such as concentration difficulties and memory deficits;
  • Depression and mood changes.

Currently, it is not yet clear with what percentage of incidence the post-polio syndrome affects former polio sufferers; the statistics in this regard, in fact, report conflicting data: according to some, the post-polio syndrome would affect 25% of former polio patients; according to others, however, it would concern well over 50% of former patients.

Curiosity

Currently, according to the most reliable estimates, in the United Kingdom, the carriers of post-polio syndrome would be about 120, 000.

When should I go to the doctor?

An individual should contact his doctor and ask for clarifications regarding the polio vaccine, if he has decided to take a trip to geographic areas of the world where polio is still a widespread disease or vaccination methods are not cutting edge.

It is recommended to contact the doctor to the parents of:

  • Children who have not completed the polio vaccination program;
  • Children who responded to the polio vaccination with an allergic reaction;
  • Children who, at the polio vaccine injection site, complain of pain.

Diagnosis

A doctor with some experience is able to recognize a patient with poliomyelitis only from the symptoms (physical examination) and from the analysis of the clinical history.

For the purposes of a correct diagnosis of polio, the most significant clinical manifestations (therefore also those most sought after by the doctor, during the physical examination) are:

  • The presence of a certain rigidity of the neck and / or back;
  • Back pain;
  • Breathing and swallowing difficulties;
  • The presence of abnormal reflexes.

What are the confirmatory tests?

The confirmation of what is shown by the critical analysis of the symptoms comes from the analysis of a biological sample, such as sputum, cerebrospinal fluid or faeces.

Therapy

For further information: Medications for the treatment of Poliomyelitis

Still today, unfortunately, the polio sufferer can only rely on symptomatic therapy (ie aimed at controlling symptoms), as doctors and researchers, despite their numerous research efforts, have not yet found a cure capable of annihilate the poliovirus, when it is in the human body, and specifically treat the resulting infection.

Purpose of symptomatic therapy

Symptomatic therapy against poliomyelitis aims to "lighten" the symptoms, so as to improve the patient's living conditions. For the patient suffering from polio, a good quality of life supports the organism, while this fights infection, and consequently reduces the risk of complications.

What is symptomatic therapy against poliomyelitis?

Symptomatic therapy varies according to the severity of the infection triggered by poliovirus. That's how:

  • In the less severe cases of poliomyelitis (minor polio and subclinical), the treatment provides, quite simply, a period of absolute rest (preferably in the hospital) and the taking of drugs to control fever and flu-like symptoms;
  • In cases of non-paralytic poliomyelitis, the therapy envisaged consists, in addition to rest and taking drugs against fever, in taking pain-relieving drugs against neck pain and back pain, and in a period of physical therapies to restore muscle tone (clearly the physical therapies must take place in a second phase, after the rest period);
  • Finally, in cases of paralytic poliomyelitis, the treatment is very complex and involves:
    • Absolute rest in equipped environments (therefore in the hospital);
    • Fever control drugs;
    • Painkillers against headaches, muscle aches and joint pains;
    • Ventilation assistance;
    • Physiotherapy and muscle strengthening exercises, in order to prevent or treat the possible consequences of temporary paralysis of the body muscles;
    • Use of braces (eg: corrective shoes), to prevent or treat deformities in the ankles and feet;
    • Appropriate diet;
    • Occupational therapy, to make the patient as independent as possible from others.
    • Use of antibiotics and urinary catheters to prevent the onset of urinary tract infections (bladder in particular).

Prognosis

For those who fall ill with poliomyelitis, the prognosis depends on the severity of the infectious process. In fact, if the poliovirus has limited itself to causing the subclinical form or the non-paralytic form, there are high chances of a complete recovery (especially in the case of subclinical poliomyelitis); vice versa, if the poliovirus has invaded the motor neurons of the brain and / or of the spinal cord, the hopes of a complete recovery are definitely lower, indeed, the probability that the patient develops permanent physical and / or cognitive disabilities or, even, go to death.

Are disabilities or death more common?

Paralytic poliomyelitis more often causes physical and / or cognitive disabilities than death. This is demonstrated by some statistics, which show that 5-10% of patients with paralytic poliomyelitis (while, obviously, disabilities affect the remaining percentage of patients).

Curiosity

If treated promptly and appropriately, spinal paralytic poliomyelitis can heal without causing complications; in other words, with the correct treatments, there is the possibility of completely recovering even from a very serious condition such as the paralytic poliomyelitis that affects the spinal cord.

In the presence of temporary paralysis, what are the recovery times?

It is possible to satisfactorily recover from a paralytic poliomyelitis that has produced temporary neurological alterations, but it takes from 6 to 8 months of accurate rehabilitative care.

Unfortunately, physiotherapy can do little with permanent paralysis.

Prevention

The best weapon to defend against an incurable disease like polio is prevention by means of a special vaccine .

Currently, the polio vaccine practiced in the most avant-garde countries is the so-called inactivated polio vaccine, as it effectively protects from all three poliovirus serotypes (PV1, PV2 and PV3) and is safe, even for those with a weak immune system .

In Italy as well as in the United States, the United Kingdom, etc., vaccination against polio is a therapeutic cycle that involves 4 administrations, of which 3 are to be performed only in the first year of life and the last in the 5th-6th year.

Theoretically, the vaccination coverage, offered by the inactivated polio vaccine, lasts a lifetime.

Among the most famous inoculated polio vaccines are: Infanrix Hexa, Infanrix Penta, POLIOVAX-IN IMSC 1 F 1 ML and IMOVAX POLIO 1SIR 0.5 ML.

When is further vaccination needed?

Doctors recommend further polio vaccination to all those who plan to travel to those countries where, due to poor sanitary conditions for example, the risk of developing polio is still high.