PARIS: Conflict in Afghanistan and vaccination problems in Pakistan have led to a rise in polio cases there, imperilling efforts to wipe out the disease worldwide, a study said Wednesday.

Newly introduced vaccines had the potential to eliminate polio in these countries if sufficient numbers of children could be reached, according to the paper, published in The Lancet medical journal.

Last year, Pakistan reported the highest number of polio cases in a decade, 198 in total, compared to 144 in 2010, while Afghanistan had 81 cases, up from 30 the year before.

“Polio eradication in Pakistan has been affected by weak service delivery,”said the paper, with fewer children reached.

“The eradication of poliomyelitis in parts of Pakistan and Afghanistan has been complicated by armed conflict, security concerns, cultural barriers and natural disasters that have limited accessibility.”

Philip Minor of the British National Institute of Biological Standards and Control, in a comment published with the study, warned the virus could spread to polio-free areas.

“Clearly, if one country has poliomyelitis the whole world is at risk,” he said.

Poliomyelitis, a crippling disease of the nervous system, was endemic in more than 125 countries in 1988, according to the World Health Organisation (WHO) website.

Today, only Pakistan, Afghanistan and Nigeria remain on the list. India was removed from it in February thanks to the impact of a massive vaccination campaign.