Transmission

transmission

Transmission is through faeco-oral route although oral-oral route may account for some cases (1). Polio virus may be isolated from the nasopharynx and faeces of infected individuals;

• after gaining access to the body through the gut or the nasopharynx, the virus multiplies in the pharynx and intestine for one to three weeks (1)
• spread occurs by way of the bloodstream to susceptible tissues or by way of retrograde axonal transport to the central nervous system (2)
• virus continues to be excreted in the saliva for two weeks and in the faeces for two to three weeks. But carriers and some immunocompromised persons may shed virus in the faeces for longer than 6 weeks (2,3)

Cases are most infectious from about immediately before and one to two weeks after the onset of paralytic disease (2)

Reference:

• (1) Centers for Disease Control and Prevention (CDC). Epidemiology and Prevention of Vaccine-Preventable Diseases. The Pink Book. Poliomyelitis
• (2) Immunisation Against Infectious Disease - "The Green Book".Chapter 26 Poliomyelitis (January 2013)
• (3) Immunisation Guidelines for Ireland (2013). Chapter 13. Poiliomyelitis