what is the primary reservoir for poliovirus
a) Agent : The causative agents is the polioviruses which have three serotypes 1,2 and 3. Most outbreaks of paralytic polio are due to tpye-1 virus. Polio virus can survive for long periods in the external environment. In a cold environment, it can live in water for 4 months and in faeces for 6 months. It is therefore well-adapted for the faecal-oral route of transmission.