GENEVA (Reuters) - The paralysing polio virus is spreading fast in Pakistan and Afghanistan, two of its last four strongholds, in areas struck by violence and mass displacement, health experts said on Thursday. A report presented to the World Health Organisations annual assembly also stressed the fragility of progress in the polio fight in India, where vaccinations are being stepped up to better-protect children in fast-growing slums. Warfare appears to be the biggest barrier to eradication in Pakistan and Afghanistan, where the number of children paralysed surged in the second half of last year, according to the report that put the last four endemic countries under the spotlight at the World Health Assembly. A deterioration in security resulted in large-scale population movements and outbreaks in polimyelitis-free areas, particularly in the Punjab province, it said. By early 2009 poliomyelitis was largely restricted to areas where insecurity hampers supplementary immunisation activities. When the Global Polio Eradication Initiative was launched in 1988, the contagious disease paralysed more than 1,000 children every day and was endemic in 125 countries around the world. It has now been stamped out - at least temporarily in all countries except four, thanks to aggressive vaccination campaigns that have cost more than $6 billion to date. But until outbreaks stop everywhere, epidemiologists say it will continue to spread and threaten more paralysis, further setting off the global eradication goal first slated for 2000.