Poliovirus
Poliomyelitis (polio) is a highly infectious viral disease that spreads from person to person through faecal-oral contact. Flies, too, can transfer the poliovirus from faeces to food. Once the virus enters the body, it multiplies in the intestines and attacks the nervous system. The incubation period for the virus is 7-10 days. After initial infection, the virus is excreted intermittently in faeces for several weeks. Initial symptoms are fever, fatigue, headache, vomiting, pain in neck and limbs.
One in 200 infections leads to irreversible paralysis (usually in the legs). The virus destroys nerve cells, which activate muscles. The limbs become floppy and lifeless: a condition known as acute flaccid paralysis (AFP). Among those paralysed, 5-10 per cent die. As most children infected with poliovirus have no signs of illness, they are never aware they have got the infection. The virus has three strains: serotype 1 is the most common, type 3 is less frequent and type 2 is rare.
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