Last week the World Health Organization (WHO) confirmed the presence of wild poliovirus type one (WPV1) in 10 children under two years old in Deir al-Zour province in the Syria's east.

These are the first reported cases of polio in the country since 1999. This is another sign of the collapse of state institutions in Syria, all these children being born after the outbreak of civil war.

As an indication of the scale of the problem among refugee and internally displaced Syrians, Medecins Sans Frontieres has estimated that as of December 2012, only 33% of Syrian refugee children in Lebanon had received standard vaccinations (p.8). Inside the country, UNICEF estimates that half a million children have missed out on polio vaccinations in the past two years. Before the conflict, about 95% of Syrian children were vaccinated.

UNICEF, WHO and the Syrian Government have now mounted a large-scale immunisation effort aimed at 2.4 million Syria children.

The large number of displaced people, their undocumented movements, and the cramped and unhygienic conditions in camps inside and outside the country lead Zaher Sahloul, president of the Syrian-American Medical Association, to describe the situation as a ‘perfect formula for spreading the epidemic out of control’.

Similarly, this is how Fouad Fouad, a Syrian doctor now based at the American University of Beirut, explains the potential spread of infectious diseases in Syria:

Infectious diseases, and vaccination-related or waterborne diseases or diseases caused by the environment like respiratory illness, are facing a medical system that has collapsed in Syria, and difficulties facing refugees when it comes to accessing services. All factors tell us that because of this, there will be an infectious disease outbreak, whether it be measles or polio or Hepatitis A or B.

 We’re talking about diseases normally protected by vaccination campaigns. Every country should have campaigns against diseases that happen in childhood, like measles, Hep A, polio and mumps. When the Syrian health system collapsed, implementing these campaigns becomes difficult in conflict areas, whether because of direct fighting or an inability to access these areas, or a lack of medical staff. When you don’t have widespread use of the polio vaccine, we call it “wild polio virus,” and it can be spread through water, soil or through contact between people.

The Syrian Government blames jihadi fighters from Pakistan for the outbreak. Pakistan and Afghanistan are two of the three remaining countries where polio is endemic, and there are reportedly hundreds of Pakistani fighters in Syria. New Scientist too suggests that the northwest Pakistan is the ‘probable source’.

Professor Michael Toole of the Burnet Institute suggests another possible (and surprising) source — Israel and the Palestinian territories:

Since February 2013, more than 100 samples of sewage have been positive for WPV1 in southern and central Israel, and more recently samples have tested positive in Gaza and the West Bank. There have been no cases of paralytic disease during this “silent” outbreak...

...More than 95% of children in Israel, Gaza, and the West Bank have been vaccinated with IPV which explains the absence of clinical disease. But if children with WPV in their gut come in contact with children who do not have adequate immunity, they may transmit the virus which may then cause paralytic disease. Given the mobility of the Bedouins, the virus may spread through Jordan, northern Egypt, and quite possibly Syria.

WHO is currently undertaking genetic sequencing to determine the origin of this particular virus.

Photo by Flickr user US Mission Geneva.