The map to the left displays the territory size as a proportion of the worldwide polio cases from 2000 to 2005. The reason for the overwhelming amount of polio cases in Nigeria? The Nigerian Muslims boycott of the Polio Vaccine. The boycott began in the northern Islamic state of Kano in Nigeria and other Nigerian states quickly followed suit. Kano state officials have insisted that the vaccine is unhealthy based on the fact that in 2003, Nigerian health experts found estrogen and other female sex hormones in the vaccine. They claim this vaccination effort to be a U.S. plot to spread AIDS and infertility. As the boycott continues, polio cases have been reported in 7 other African countries where it was previously believed to be eradicated.