Syria’s polio outbreak has now officially spread to Iraq, the first neighbor of the war-ravaged country to be hit by the crippling virus despite an ambitious Middle East inoculation effort, and global health officials warned Monday that dozens of vulnerable Iraqi children could potentially be infected.

The transmission of polio, a highly contagious disease that primarily afflicts children younger than 5 and can lead to partial and sometimes fatal paralysis, reflects one of the most insidious effects of the three-year-old Syria conflict, which has sent millions of refugees across the country’s borders and severely undermined its public health system.

For Iraq, the outbreak is the first time in 14 years that polio has appeared; the disease was absent even during the 2003-2011 war that began with the American-led invasion to topple Saddam Hussein.

World Health Organization officials said the first Iraqi polio case, that of a 6-month-old boy in Baghdad, was confirmed on March 30 by Iraq’s Ministry of Health and had the same genetic fingerprint as the virus that paralyzed 27 children in eastern Syria in October — both having originated in Pakistan, one of the few countries in the world where polio has not been eradicated. The Polio Global Eradication Initiative, a partnership that includes the W.H.O., reported two new Syria cases last week — in Aleppo and Hama, far from the original outbreak area.