An emergency vaccination drive is underway in Kenya to control an outbreak of polio in the Dadaab refugee camp. According to authorities, the disease is so virulent that for every one infection, there are at least 200 to 300 other people who are also carrying the virus. The World Health Organization believes it is possible to eradicate polio within the next decade, but only if outbreaks like Dadaab's can be quickly controlled. Al Jazeera's Peter Greste reports from the camp in northeastern Kenya.