Polio 2010

Poliovirus

Over the next few weeks, Inside Vaccines will be taking a closer look at Poliomyelitis infections, exploring aspects of the history of poliomyelitis; describing environmental factors that increase the incidence of paralytic polio; considering the history and efficacy of the vaccines used against polio; and finally, exploring the campaign to eradicate polio.
First, let’s look at some basic information.

When most people think of poliomyelitis, they think of children who had lameness and leg deformities, with their legs in braces, or lying in iron lungs (old-style breathing machines, or ventilators) because they couldn’t breathe. Most people link all paralysis and lameness solely to a group of viruses called POLIOMYELITIS. The World Health Organization describes polio:

Polio is a highly infectious disease caused by a virus. It invades the nervous system, and can cause total paralysis in a matter of hours. The virus enters the body through the mouth and multiplies in the intestine. Initial symptoms are fever, fatigue, headache, vomiting, stiffness in the neck and pain in the limbs. One in 200 infections leads to irreversible paralysis (usually in the legs). Among those paralysed, 5% to 10% die when their breathing muscles become immobilized. [1]

Now for a more accurate picture of exactly what “poliomyelitis” is.

The poliomyelitis viruses fall within a class of viruses called “human enteroviruses” [2]. Polioviruses belong to the viral family Picornaviridae [3]. There are three types: 1 Brunhilde; 2 Lansing; and 3 Leon.   Amongst these types there are hundreds of different strains. Type 1 is considered the most serious virus, followed by type 2.

Technically, a person can “get” poliomyelitis 3 times, since the types do not give cross protection to each other, but in practice, having clinical polio three times is very rare.

How is poliomyelitis virus transmitted?

Poliomyelitis is transmitted by person-to-person spread through fecal-oral and oral-oral routes, or occasionally by a common vehicle (e.g., water, milk). [4]

What happens when people are exposed to polioviruses?

When non-immune persons are exposed to wild poliovirus, inapparent infection is the most frequent outcome (72 percent). [4]

Most people won’t even be aware that they were sick. Read more

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