Most common mode of transmission of polio virus-

Ans. is 'b' i.e., Fecal-oral routeo Polio transmission is mostly restricted to developing countries where fecal-oral route is the most common mode of transmission.Polio Viruso Belongs to Picomaviruso A nonenveloped RNA virus (ss RNA).o Has four viral proteins, VP1-VP4. VP 1 Carries the major antigenic site.o Three types - Type 1,2 and 3o Type 1 is most common and causes most epidemicso Type 2 usually causes endemic infectionso Type 3 also causes epidemics.Pathologyo Virus multiplies selectively in neurons and destroys them,o Earliest change - Chromatolysis (Degeneration of nissel bodies)o Lesions are mostly in the anterior horns of the spinal cord.Some important points about poliovirus strains* (Type I. II. III)o Most common cause of epidemics*- Type Io Most difficult to eradicate* - Type I (because vaccine response to it is not good)o Most common cause of vaccine induced paralytic poliomyelitis*-Type III (due to mutation)o Most commonly associated with paralysis* -Type Io Most effective antigen -Type IIModes of transmission1. Fecal-oral route-Most common in developing countries.2. Droplet infection-More important in developed countries (through inhalation or through conjuctiva)