The push to eradicate polio from the world took more than one bullet last week. On 20 July, Muhammad Ishaq, a local worker with Pakistan's polio eradication programme, was shot dead in Gadap, a district of Karachi in southern Pakistan.

Three days earlier polio drives in the area were suspended when a Ghanaian doctor and his driver were shot and wounded as they drove through Gadap.

The shootings follow a ban on polio vaccination in northern Pakistan, declared in June by Hafiz Gul Bahadur, a Taliban commander. Bahadur is using the ban as an attempt to force a halt to US drone attacks.

Hostility to polio vaccination also rose after US agents used vaccination campaigns to gain access to families during the search for Osama bin Laden. A Pakistani physician alleged to have helped the CIA was sentenced to 33 years in prison in May.

Pakistan, Nigeria and Afghanistan are the only countries where wild polio virus persists, with Pakistan considered the toughest hold-out. Gadap is one of three strongholds of the virus in Pakistan, and as an urban area with many migrant families it is a source of outbreaks elsewhere in the country.

Hopes had risen that the programme was working, as no cases of polio have been reported in Karachi so far this year, after nine last year. Also, anindependent assessment of the polio eradication drive reported in June that water samples from Gadap were virus-free. The assessors attributed the progress to local workers – like Ishaq.