All of the following statements are true regarding polio-virus except:
Ans. (c) There is a single serotype causing infection Impoant features of Polio virus Poliovirus, causative agent of polio, is SS positive sense RNA virus having 1, 2 and 3 serotypes. MC serotype - Type 1 MC cause of epidemic - Type 1 (epidemics are also caused by Type 3 while endemics are by Type 2) MC type associated with paralysis - Type 1 Most difficult to eradicate Type -1 Most antigenic - Type 2 MC cause of vaccine induced paralysis - mutated Type - 3 Modes of transmission Main route: Feco-oral route directly or indirectly. Droplet infection: May occur in acute phase of disease. Clinical Spectrum Most vulnerable age is between 6 months and 3 years. M.0 clinical presentation - Inapparent / subclinical infection. Most rare clinical presentation - Paralytic polio. Usual cause of death - respiratory insufficiency. Progressive paralysis, coma or convulsions usually indicate cause other than polio. Prevention Two types of vaccine: Inactivated (salk) injectable polio vaccine. Oral (sabin) live attenuated vaccine: It provides both local immunity (by producing intestinal IgA) and systemic immunity. Vaccine progeny is excreted in feces and secondary spread occurs to household contacts so non immunized persons are immunized by replacing wild strain by vaccine strain. It results in herd immunity even if only about 66% of community is immunized. T I P S Typhoid oral Influenza Plague Sabin B Y E BCG Yellow Fever Epidemic typhus C2 M M R Chicken pox Cholera Measles Mumps Rubella Vaccine Derived Poliovirus Vaccine associated paralytic poliomyetitis is seen in 4 case/10 lakh bih Clinical features are exactly same as that seen with wild poliovirus. It is most frequently associated with sabin 3 (60% of cases) followed by sabin 2 and sabin 1. In patients with common variable immunodeficiency syndrome, sabin virus replicate for prolong periods, resulting in chronic shedding of vaccine derived poio virus with increased neurovirulence, Such viruses are termed as immunodeficiency associated vaccine derived poliovirus (iVDPV). Note: HIV or AIDS are risk factors for the development of iVDPV
It is transmitted by feco-oral route
Asymptomatic infections are common in children
There is a single serotype causing infection
Live attenuated vaccine produces herd immunity