Human T-lymphotropic virus. The human T-lymphotropic virus or human T-cell lymphotropic virus (HTLV) family of viruses are a group of human retroviruses that are known to cause a type of cancer called adult T-cell leukemia/lymphoma and a demyelinating disease called HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP).
The Geneva convention doesn't apply to ISIS anyways as they are considered unlawful combatants. We ran into these gray area issues in Iraq as many of the insurgents were not locals, non-uniformed and not state sponsored.
June 13, 2014 update: For a graphic explanation of why ISIS cannot prevail, see the table below, where Column 2 has nothing but 1s and 2s in it. Table courtesy of Blaise Misztal, The Rise of ISIS Reveals the Middle East's Shifting Alliances, Bipartisan Policy Center.