True about polio :

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