* Crippling virus confirmed in Deir al-Zor province
* UNICEF calls for vaccination of 500,000 Syrian children
* Seven Middle East nations plan to vaccinate 20 million
* Virus believed to have originated in Pakistan
By Stephanie Nebehay
GENEVA, Oct 29 (Reuters) - Polio has broken out among youngchildren in northeast Syria after probably originating inPakistan and poses a threat to millions of children across theMiddle East, the World Health Organisation (WHO) said onTuesday.
The crippling disease, which is caused by a virustransmitted via contaminated food and water, could spreadespecially fast in Syria, where civil war has led to fallingvaccination rates.
Twenty-two children in Deir al-Zor province bordering Iraqbecame paralysed on Oct. 17 and the polio virus has beenconfirmed in samples taken from 10 victims. Results on the other12 are expected within days.
"This virus has come over land which means the virus is notjust in that corner of Syria but in a broad area," BruceAylward, WHO assistant director-general for polio, emergenciesand country collaboration, told Reuters in an interview.
"We know a polio virus from Pakistan was found in the sewageof Cairo in December. The same virus was found in Israel inApril, also in the West Bank and Gaza.
"It... is putting the whole Middle East at risk quitefrankly," he said by telephone from Oman.
Polio, which invades the nervous system and can causeirreversible paralysis within hours, can spread rapidly amongchildren under five, especially in the unsanitary conditionsendured by the displaced in Syria or crowded refugee camps inneighbouring countries.
It is endemic in just three countries - Nigeria, Pakistanand Afghanistan - raising the possibility that foreign fightersimported the virus into Syria, where Islamist militants areamong the groups battling to oust President Bashar al-Assad.
Genetic sequencing of the virus found in Syria is expectedwithin the next days, which will identify the geographic originof the first polio outbreak in the war-torn country since 1999.
"Everything suggests this virus will be linked to the virusthat originated in Pakistan," Aylward said.
"We are looking basically at re-infection of the MiddleEast. Syria is the canary in the coal mine," he said.
Most of the 22 Syrian victims are under two years old andare believed never to have been vaccinated or to have receivedonly a single dose of the oral vaccine instead of the threewhich ensure protection, WHO spokesman Oliver Rosenbauer said.
"Immunisations have started in that area," Rosenbauer said,referring to Deir al-Zor, whose main city is partly controlledby Assad forces while rebels hold the surrounding countryside.
A previously planned immunisation campaign was launched inSyria on Oct. 24 to vaccinate 1.6 million children againstpolio, measles, mumps and rubella, in both government-controlledand contested areas, the WHO said on Tuesday.
Anthony Lake, executive director of the U.N. Children's Fund(UNICEF), said he had held "businesslike and encouraging" talkswith Syrian Prime Minister Wael al-Halqi in Damascus.
He called for the estimated half a million Syrian childrenwho have not been vaccinated against polio and otherdebilitating diseases because of the war to be vaccinated.
Syria has about three million under-5s in total.
As well as Syria, Aylward said at least six other MiddleEast nations - Egypt, Iraq, Turkey, Lebanon, Jordan and thePalestinian territories - plan polio immunisation campaigns.
"This will cover over 20 million children in the nextmonths," he said.
The campaigns are likely to begin in early November and tolast at least six to eight months, the WHO said in a statement.
About 4,000 refugees flee the war in Syria every day, mainlycrossing into Lebanon, Iraq, Jordan and Turkey.
Before the conflict, which began with peaceful protests inMarch 2011 and led to a civil war, 91 percent of Syrian childrenhad been vaccinated against diseases including polio, but therate has fallen to about 68 percent, Rosenbauer said.
"So it makes sense that very young kids would get it."