Epidemiology - Poliovirus

Epidemiology

Poliovirus mainly affects children. However, individuals of any age may also develop the disease.

◗ Geographical distribution

Polio continues to remain a major public health problem in developing countries. Six countries have been identified as endemic for poliomyelitis in the year 2003. These include Afghanistan, Egypt, Niger, Nigeria, Pakistan, and India. Significant progress has been made in reducing the prevalence of poliomyelitis in India. Efforts have been recently maximized to eliminate poliovirus infection in the very near future.

◗ Reservoir, source, and transmission of infection

Natural infection occurs only in humans. Infected humans excreting poliovirus in their stool are the major reservoir of infection. Infected stool containing poliovirus is the major source. The viruses secreted in throat secretions during early stage of the illness may also be another source of infection. The poliovirus is transmitted:

·           primarily by the fecal–oral route by ingestion of food and water contaminated with human feces.

·           by inhalation or through fomites contaminated with respi-ratory secretions.

Poor sanitation, low socioeconomic status, and crowded living conditions facilitate transmission of infection. Immunocompromised patients, such as those with HIV infec-tion, B cell dysfunction, and IgA deficiency are particularly at high risk of developing poliomyelitis when exposed to poliovirus.