A Syrian refugee girl helps her brother, who the family suspects has polio, in a mosque compound in Shebaa, Lebanon. Following news of polio outbreak in Syria, the country and its neighbors announced emergency vaccination programs. (Jamal Saidi/Reuters)

Ten Syrian children have tested positive for polio, the World Health Organization said Tuesday, sparking fears of a major regional outbreak amid mass migration and the collapse of Syria’s health services under the pressures of civil war.

Health officials warned of a significant risk of the highly infectious disease spreading after the cases were confirmed in the eastern province of Deir al-Zour.

In addition to those cases, the officials said, 12 other children suffering from paralysis associated with polio are awaiting test results, meaning that thousands more are likely to be infected, because just 1 in 200 of those who contract the disease show such symptoms.

“The confirmed cases are just the tip of the iceberg,” said Bruce Aylward, assistant director general for polio and emergencies at the WHO. “It could explode.”

The 2 1 / 2-year-long conflict in Syria has created optimal conditions for the spread of communicable diseases, devastating the country’s health-care system and disrupting routine immunization programs.

A look at the history of the polio inoculation program.

Health workers have warned that the unsanitary conditions in which many of the millions of displaced Syrians live are breeding grounds for diseases such as polio, which is transmitted through contaminated food or water supplies. With as many as 4,000 refugees fleeing the country every day, the risk of the disease spreading is particularly serious.

“It’s the perfect storm into which to drop the polio virus,” Aylward said. “This isn’t a Syrian problem. This is a Middle Eastern problem, which is going to require a massive multi-country response.”

That response is already underway. Seven countries in the region, including Syria and neighboring Jordan, Turkey and Lebanon, have launched emergency programs to vaccinate 20 million children over the next two months, with follow-up rounds in the most at-risk areas into the new year, he said.

The outbreak marks a setback in the campaign to eradicate polio worldwide. The disease paralyzed 1,000 children a day when the global effort to stamp it out, led by the WHO, the Rotary Foundation and UNICEF, began 25 years ago. Despite the more than 99 percent drop in cases, the final push has proved challenging.

The disease, which usually affects children younger than 5, can cause permanent paralysis within hours. Some cases result in death as respiratory muscles freeze up. There is no known cure.

The cases confirmed in Syria are the first in the country in 14 years. Most involve children younger than 2, born after the conflict began in early 2011 and only partially vaccinated or not vaccinated at all.

The immunization rate in the country, which stood at 91 percent in 2010, has plummeted to 68 percent today, according to the WHO, amid a war in which health facilities have been targeted.

U.N. humanitarian aid chief Valerie Amos is calling for stronger action to increase humanitarian aid to Syria. (The Washington Post)

Doctors and health-care workers have fled the country in massive numbers, and those who remain work under threat and without supplies as combatants on both sides have taken over or destroyed hospitals, U.N. humanitarian chief Valerie Amos said in an interview in Washington on Monday.

Destruction of water-treatment facilities, electric power plants and other infrastructure has left Syrians “on average with only one-third the daily water” supply that was available to them before the conflict, much of it contaminated, she said.

It is not known how polio was transmitted to Syria, but genetic sequencing tests are being undertaken to pinpoint the outbreak’s origin. Aylward suspects that it will be traced to Pakistan; the Pakistani strain has been detected in environmental samples in Egypt and Israel.

Polio is not the only disease causing concern in Syria, with cases of hepatitis, tuberculosis and measles also on the rise, according to relief workers, who are pushing for better cross-border aid access as winter approaches.

Amos said that at least 2,000 groups are fighting in Syria and that U.N. humanitarian workers have been unable to reach nearly 3 million Syrians in need because they are prevented at government or opposition checkpoints from traveling to some areas by road.

More than 300,000 of those in need are in what Amos called “besieged communities,” occupied by combatants from one side or the other who stop civilians from leaving and block the entry of food and medical care.

The bulk of besieged civilians are in an eastern Damascus suburb that has been surrounded by government forces since early this year and was targeted in a chemical weapons attack in August, Amos said. But in other areas, such as Aleppo in the north, she said, rebels are hindering access.

With near-constant fighting, she said, “the numbers of those in need are going to go up . . . exponentially” in the next few weeks and months.

A sliver of hope came Tuesday as hundreds of residents of ­Moadamiya, a rebel-held district southwest of Damascus that has been under siege by government troops for nearly a year, were evacuated in a deal brokered by President Bashar al-Assad’s government and Mother Agnes, a nun who has been a vocal Assad supporter since the uprising began. An earlier evacuation attempt ended when shells fell in the area where civilians were waiting for the buses, activists and field doctors said.

One person was killed, they said, leaving many wary of another attempt. However, with 11 reported cases of death from malnutrition, many thought they could no longer stay, said Qusai Zakarya, an opposition activist in the area. He said 800 women and children were evacuated Tuesday.

“Unfortunately, the people have had no choice but to take this offer,” he said. “The whole damn world failed to get in a piece of bread for the people of Moadamiya. We witnessed all kinds of death by Assad, even sarin gas, but we cannot stand the hunger.”

The evacuation comes amid a diplomatic push to secure better humanitarian access into Syria ahead of a planned peace conference in Geneva next month, in hopes that improvements may encourage the opposition to participate.

The planned talks have set off a flurry of diplomacy, with Lakhdar Brahimi, the U.N.-Arab League envoy to Syria, visiting Damascus this week to shore up attendance.

However, one interlocutor, Qadri Jamil, Syria’s deputy prime minister, was dismissed Tuesday for “activities and meetings outside the country without prior coordination with the government,” the state-run Syrian Arab News Agency reported.

The State Department confirmed Tuesday that Jamil had met in Geneva on Saturday with U.S. diplomat Robert Ford. Jamil had requested the meeting some time ago and made it clear that he was “speaking only for himself and not in any official capacity,” according to a senior Obama administration official who was not authorized to discuss the matter on the record.

Jamil, who is part of what is dubbed the “patriotic opposition” tolerated by the Syrian government, told Ford that he “wanted to be in the opposition delegation” to the Geneva talks, the official said. “Ambassador Ford told him he ought to speak to the Syrian Opposition Coalition, not to” Ford.

The official said it was unclear whether Jamil, who reportedly traveled to Moscow from Geneva, had been fired, as the government said, or had resigned or defected.

DeYoung reported from Washington. Ahmed Ramadan in Beirut contributed to this report.