<prompt> True about polio :Paralytic polio is most commonSpastic paralysisIncreased muscular activity leads to increased paralysisPolio drop given only in 3 year  <response>: increased muscular activity increases the risk of paralytic polio The incubation period of poliovirus from contact to initial clinical symptoms is usually considered to be 8-12 days with a range of 5-35 days. Poliovirus infection may follow one of the several courses: i Inapparent infection It occurs in 80-95 of cases and causes no disease and no sequale ii Aboive poliomyelitis It occurs in about 5 of patients. It is a non specific influenza like syndrome which occurs 1-2 week after infection. Fever, malaise, anorexia and headache are prominent features and there may be sore throat and abdominal or muscular pain. The illness is sholived for upto 2-3 days. The physical examination may be normal or may reveal nonspecific pharyngitis, abdominal or muscular 1 tenderness and weakness. Recovery is complete and no neurological signs or sequalae develop. iii Nonparalytic poliomyelitis It occurs in 1 of patients infected with poliovirus. They present as soreness and stiffness of the posterior muscles of the neck, trunks and limbs. iv Paralytic poliomyelitis Paralytic poliomyelitis develops in about 1 patients causing 3 clinically recognizable syndromes which are i Spinal paralytic poliomyelitis ii Bulbar poliomyelitis iii Polioencephalitis Pulse polio immunisation is given to all children less than 5 years of age not 3 years of age The risk factors found to precipitate an attack of paralytic polio in individuals infected with polio include: Physical activity immediately following onset of paralysis Skeletal muscle injury due to injection of vaccines or therapeutic agents Pregnancy Malnutrition Immune deficiency Tonsillectomy 