Islamabad, Sep 26 : Traces of wild poliovirus type 1 have been found in sewage samples collected from two different parts of Pakistan, the Health Ministry said on Tuesday. A sewage sample collected from the southern port city of Karachi on September 5 and two samples collected from the Hangu district of northwest Khyber Pakhtunkhwa province the following day tested positive for the virus, the Ministry said in a statement. A national polio campaign will start from October 2 to vaccinate over 40 million children under five years of age, the ministry said, adding that all children in Hangu and Karachi would be vaccinated during this drive, reports Xinhua news agency. "We are launching a nationwide polio vaccination campaign in October to build children's immunity," caretaker Health Minister Nadeem Jan was quoted as saying in a statement. "Parents must ensure that their children under five years of age are immunized in this campaign and their routine vaccinations are up to date," he added. Pakistan has so far reported two polio cases this year and 27 positive environmental samples, according to the Ministry. Pakistan and Afghanistan are the only two endemic countries where polio is still prevalent. /IANS