For a region to be declared polio-free, there must be no cases of the disease for three years. However, over 540 cases of wild polio virus have been detected in India so far this year, thwarting the World Health Organization's (WHO's) goal of eradicating polio worldwide by 2005. India has recorded two-thirds of the polio cases seen worldwide in 2002, with 446 cases in Uttar Pradesh alone. Experts say there could be as many as 1,000 cases of the disease by year-end. Arun Thapa, the WHO's regional advisor for polio, notes that part of the problem in trying to vaccinate all children against polio is distrust, as some mistakenly believe that the polio vaccine will make their children impotent or that it is tainted with HIV.