Poliomyelitis

Polioviruse, that targeting motor neurons

Poliomyelitis is caused by three serotypes of poliovirus, a neurotropic RNA virus of the family Picornaviridae, genus Enterovirus.

Poliovirus type 1 has the highest ratio of paralytic infection to subclinical infection and is the most frequent cause of epidemics of paralytic disease. Poliovirus types 2 and 3 are less neurovirulent. Type 2 wild poliovirus was the first serotype to be eradicated in the Americas; as of 1999, the only remaining foci of type 2 wild poliovirus transmission were detected in northern India . Type 3 wild poliovirus caused a major outbreak of paralytic disease in Angola in 1999 .

Poliomyelitis is transmitted by person-to-person spread through facial-oral and oral-oral routes, or occasionally by a common vehicle (e.g., water, milk). The incubation period is typically 7-14 days (range, 3-35 days). When nonimmune persons are exposed to wild poliovirus, inapparent infection is the most frequent outcome. 

Acute flaccid paralysis (AFP) is a clinical syndrome characterized by rapid onset of weakness, including (less frequently) weakness of the muscles of respiration and swallowing, progressing to maximum severity within several days to weeks. The term "flaccid" indicates the absence of spasticity or other signs of disordered central nervous system motor tracts such as hyperreflexia, clonus, or extensor plantar responses.

The differential diagnosis of AFP varies considerably with age. No single operational clinical case definition of AFP or paralytic poliomyelitis that combines both high sensitivity and high specificity has emerged. The currently used case definition increases sensitivity in detecting the existence of AFP but tends to decrease specificity in detecting paralytic poliomyelitis. 

"Paralysis" means loss of contraction due to interruption of motor pathways from the cortex to the muscle fiber. It is preferable to use the term "paresis" for slight loss of motor strength and "paralysis" or "plegia" for severe loss of motor strength. It is the disease of nervous system. It is divided into two parts -

1. Sensory - Loss of senses

2. Motor - Loss of movements

It can occur simultaneously or individually. It can be further divided into following types.

a. Ascending motor Paralysis - Paralysis starting in lower parts & going to upper parts of the body.

b. Locomotor Ataxia, Paraplegia - Paralysis of lower limbs

c. Paralysis Agitans - Trembling of paralyzed parts such as upper limbs, face, lower limbs or whole body.

d. Facial Paralysis - Paralysis of face either right or left.

e. Hemiplegia - Paralysis of half side of the body either right or left.

f. Monoplegia - Paralyses of a single limb.

Causes of Paralysis

1. Cerebrovascular Injury ( Injury to blood vessels of brain)

2. Encephalitis (Inflammation of brain)

3. Multiple Sclerosis

4. Hysterical paralyis

5. Thrombosis (Blood clots in the circulation)

6. Parkinsonism

7. Injury to spinal cord