Do You Know The Different Types Of Polio?

The different types of polio are all infectious diseases that mainly affect the patient’s nervous system. As stated by international sources such as the World Health Organization, the polio virus, which is composed of RNA and a protein capsid, causes this disease.

According to several studies, experts have distinguished three serotypes (different varieties) of poliomyelitis. Experts discovered the last case of serotype PV-2 in India in 1999. Thus, this disease is considered eradicated.

Nevertheless, the serotypes PV-1 and PV-3 are still circulating in some populations. Both are highly contagious and cause paralytic poliomyelitis.

About polio and its spread

The World Health Organization reported figures on polio that allow people to get an idea of ​​the global situation of the polio virus. We summarize a few things:

• In 1988, when the global battle against this disease began, more than 350,000 cases were discovered worldwide.
• As a result of containment and vaccination efforts, only 18 cases were reported worldwide in 2018. That’s a 99% reduction.
• This disease mainly affects children under the age of five.

As you can see, polio is in fact a disease of the past. Nevertheless, caution is advised. Experts estimate that if the virus is not completely eradicated from its last strongholds, more than 200,000 new cases could emerge in less than 10 years.

The different types of polio

Clinical studies show that there are four main types of polio. We list them for you:

• Asymptomatic or subclinical polio. It makes up about 90% of global cases.
• Minor non-CNS disease. Causes up to 9% of cases. It causes fever, malaise, nausea, vomiting, diarrhea and constipation.
• Non-paralytic aseptic meningitis. This variant causes 1 to 2% of cases.

• Paralytic poliomyelitis. This concerns less than 1% of the cases.

Since the first two types are benign in their development, we will turn our attention to non-paralytic aseptic meningitis and paralytic poliomyelitis. Below we explain everything you need to know about both variants.

Non-paralytic aseptic meningitis

According to scientific research (Spanish link), aseptic meningitis is an infectious process that affects the meninges of the central nervous system (CNS) and causes it to swell. It causes the following symptoms:

• Fever
• Headache and stiff neck
• General malaise
• muscle strain
• Loss of appetite and vomiting

According to other bibliographic sources (Spanish link), viral aseptic meningitis (as caused by the polio virus) has a good prognosis. It’s not just polio virus that causes it. In fact, enteroviruses, herpes viruses, or HIV can also cause this condition.

Despite the fact that this condition is benign, hospitalization and the administration of antibiotics may be necessary. We say antibiotics, even though it’s caused by viruses. Doctors will immediately initiate this treatment in the most affected patients as a preventative measure against a much more dangerous bacterial meningitis.

Paralytic poliomyelitis

This is the most serious manifestation of polio. The sources cited above estimate that one in 200 patients will develop irreversible paralysis, of which up to 10% will die from respiratory muscle problems.

Detecting this severe variation is a simple task, as the symptoms are very aggressive. Bibliographic sources (Spanish link) report that five days after infection, various processes occur such as intense myalgias (muscle pain) and restrictive muscle spasms.

These phenomena then culminate in chronic weakness of the limbs. The paralysis usually reaches its peak within a week of infection. The death rate in the acute phase is 5 to 20%. The worst part is that there is no cure once the disease has manifested itself.

The paralysis will usually improve over the years after these critical phases. This is due to a process of reinnervation (Spanish link) that the neurons that remain undamaged undergo. Depending on the affected area, there are three types of paralytic poliomyelitis, namely:

• spinal polio
• bulbospinal polio
• bulbar polio

50% of patients who survive this severe manifestation subsequently suffer from weakened muscles for life. 20% to 85% of patients who have had polio as a child may develop post-polio syndrome. It causes progressive muscle atrophy that limits functional capacity.

What to Remember About the Different Types of Polio

As we have explained in this article, polio – officially poliomyelitis – is a disease that is under control in most parts of the world. In addition, 90% of cases are asymptomatic, and therefore a clinical picture is unlikely to be associated with poliovirus today.

On the other hand, there are highly effective oral and intravenous polio vaccines, with 99% protection after three doses. If global efforts to eradicate polio continue, polio will soon be a thing of the past.