World Health Organisation officials said yesterday they were stepping up surveillance and vaccinations from west Africa to east Asia in response.
Dr Bruce Aylward, who is leading the WHO's polio eradication programme, and has monitored the outbreak from its source in Nigeria in 2003, said the next month would be critical.
"If it gets into an area of low coverage then boom! We have an outbreak," he told The Independent from Geneva.
Saudi authorities have reported three cases of the crippling and sometimes fatal disease including one this week of a boy from Nigeria who has been living in a camp near Mecca. The kingdom had been polio-free since 1995 but a case emerged late last year after doctors became concerned over a Sudanese girl who became paralysed in the port city of Jeddah. Saudi officials said they had vaccinated nearly one million people in a bid to contain the risk before pilgrims arrived.
The haj, an annual pilgrimage to Mecca, is a duty of all able-bodied Muslims at least once in a lifetime. During the pilgrimage hundreds of thousands live for days in a tent city near Mecca with little or no sanitation. These conditions are ripe for transmission of the virus.
Nigeria is among the six countries that have never halted polio and Dr Aylward said the current outbreak can be traced back to a vaccine boycott led by Muslim clerics in the northern province of Kano. Local imams spread rumours that the medicine was part of a US-led plot and would make women sterile, spread Aids among men and that it might contain pork products. Scores of polio infections resulted and the virus moved through Chad and Sudan, before reaching the coast at Port Sudan. Doctors suspect that it crossed the Red Sea to Jeddah.
"Saudi Arabia would have been a dead end [for the virus] under normal circumstances but for the haj," said Dr Aylward.
WHO monitors now face a tense wait to see if populous Muslim countries with pockets of low-vaccine coverage such as Indonesia and Bangladesh will throw up new cases.
The outbreak underlined the importance of global efforts to eradicate the disease by the end of the year, a project that will take a step forward this month with the launch of a vaccination programme covering 20 countries and 80 million children.
The number of new polio cases rose 50 per cent worldwide last year to 1,200 with 782 of those in Nigeria.Reuse content