What is the structure of poliomyelitis?

Poliovirus is a member of the family of picornavirus. Picornaviruses are small, about 300 angstroms in diameter, and are comprised of an icosahedral protein coat and a single-stranded positive sense RNA genome. Poliovirus infection occurs by the fecal-oral route.

How does the polio virus work?

When poliovirus encounters the nerve cells, the protruding receptors attach to the virus particle, and infection begins. Once inside the cell, the virus hijacks the cell’s assembly process, and makes thousands of copies of itself in hours. The virus kills the cell and then spreads to infect other cells.

What are the stages of poliomyelitis?

Two phases of acute poliomyelitis can be distinguished: a nonspecific febrile illness (minor illness) followed, in a small proportion of patients, by aseptic meningitis and/or paralytic disease (major illness).

What structures does poliovirus have at the 3 end?

RNA-dependent RNA polymerase of the poliovirus adds two uracil nucleotides (UU) to VPg protein with utilizing the poly(A) tail at the 3′-end of the +ssRNA genome as a pattern, for synthesis of the negative-strand antigenomic RNA.

What are the signs and symptoms of poliomyelitis?

Progression to maximum paralysis is rapid (2–4 days); paralysis is usually associated with fever and muscle pain, and rarely progresses after the temperature has returned to normal. Spinal paralysis is typically asymmetric, more severe proximally than distally, and deep tendon reflexes are absent or diminished.

When was the last outbreak of poliomyelitis in the United States?

In 1960, a total of 2,525 paralytic cases were reported, compared with 61 in 1965. The last cases of paralytic poliomyelitis caused by endemic transmission of wild virus in the United States were in 1979, when an outbreak occurred among the Amish in several Midwest states. The virus was imported from the Netherlands.

What is the ratio of inapparent to paralytic polio?

The ratio of cases of inapparent infection to paralytic disease among susceptible individuals ranges from 100:1 to 1000:1 or more. Following poliovirus exposure, viral replication occurs in the oropharynx and the intestinal tract.

How long does flaccid paralysis last from polio?

Fewer than 1% of all polio infections in children result in flaccid paralysis. Paralytic symptoms generally begin 1 to 18 days after prodromal symptoms and progress for 2 to 3 days. Generally, no further paralysis occurs after the temperature returns to normal.