KARACHI: A six-day polio eradication campaign was launched in 21 districts of Sindh on Monday amid tight security to inoculate over 6.7 million children under age of five, Emergency Operation Centre for Polio (EOC) Sindh said. EOC Sindh Coordinator Fayaz Jatoi said the campaign would continue till September 3 in Karachi, Sukkur, Larkana, Shikarpur, Khairpur, Qambar, Shahdadkot, Jacobabad, Ghotki, Kashmore, Hyderabad, Jamshoro, Matiari, Shaheed Benazirabad, Naushero Feroze, Dadu and Sanghar. In Karachi, 8089 vaccination teams have been deployed in the six districts with around 5000 police force for their security. He said in Karachi, 2.2 million under-five children would be the target. According to World Health Organization, poliomyelitis (polio) is a highly infectious viral disease, which mainly affects young children. The virus is transmitted by person-to-person spread mainly through faecal-oral route or, less frequently, by a common source (e.g. contaminated water or food) and multiplies in the intestine, from where it can invade nervous system and can cause paralysis. Polio remains endemic in Pakistan and Afghanistan. During the last three years, there has been a decline in polio cases in Pakistan. In the year 2014, 306 cases were reported whereas 54 reported last year. This year, 13 cases have been reported so far out of which Sindh province stands at second with four: two in Shikarpur, one each in Karachi and Jacobabad. Khyber Pakhtunkhwa is the highest with seven cases.