News that Syria now faces its first polio outbreak since the virus was eradicated there back in 1999 highlights the public health side of the tragedy. Syrians face not only horrific violence perpetrated by both the Syrian government and the Syrian opposition but also a lack of clean water and a resurgence of preventable diseases.

Disease does not simply erupt spontaneously. There is always a patient zero or a catalyst. Disease is evidence that is often illuminating. Historians of China have used medical records relating to the spread of syphilis to document early modern European trade routes.

When I was in Yemen in 1995, locals warned me (superfluously) that I should not drink the mountain well water without first boiling it. The problem? Egyptian troops intervening in Yemen’s 1962-1970 civil war found it funny to relieve themselves in wells. The result? A giardia outbreak which continues to this day.

The Syrian polio outbreak now seems not simply to be the result of the collapse of state infrastructure, but also the inflow of jihadis from polio-prone areas. According to news reports:

Polio that has crippled at least 13 children in Syria has been confirmed as being caused by a strain of the virus that originated in Pakistan and is spreading across the Middle East, the World Health Organization said. Genetic sequencing shows the strain found in Syrian children in Deir al-Zor, where an outbreak was detected last month, is linked to the strain of Pakistani origin found in sewage in Egypt, Israel and Palestinian territories in the past year.

While the World Health Organization has moved to quash speculation that Pakistani jihadists unwittingly carried the Pakistani polio strain into Syria, there are no other likely alternate explanations. Certainly, there has been no influx of Pakistani 2-year-olds into a region of Syria so engulfed in civil war. The Syrian government has jumped at that theory that Pakistani jihadis introduced the virus. And while the Syrian regime may be noxious, that does not mean they are wrong. Because scientists have also detected the Pakistani strain in Egypt, Israel, and the Palestinian territories, transmission into the Syrian outbreak zones might have as easily been transmitted via Egyptians or Palestinians fighting in Syria.

While the World Health Organization has redoubled its vaccination efforts in Syria, the Syrian outbreak originated outside. It is not easy to enter Syria, even as a jihadist joining the Syrian resistance. Fortunately, these fighters are helped by officials in neighboring countries turning a blind eye at airports alongside Syria’s borders. Perhaps it’s time for Turkey, Jordan, and Iraq to end their willingness to look the other way as unvaccinated third-world jihadis transit their countries on their way to cause mayhem in Syria.