Under normal circumstances, if those wounds were not wrapped in gauze, allowing the residual undead forces lingering in them to be exposed to direct sunlight, the warm rays of the sun would slowly dissipate the undead forces residing within the wounds.
Unfortunately, although their wounds had scabbed over on the surface and stopped bleeding after being treated, they had unconsciously wrapped the wounds with gauze to reduce the risk of infection with toxin.
Unbeknownst to them, with the wounds wrapped in gauze, the undead forces that were originally lingering on the wounds lost the suppression of the sunlight during the day due to the bandages' blockage, which inadvertently increased the chance of infection and incubation.
