Le Paradis Pour Toi

Losang and the other members of the abbey believe Laurent to be immune to the Wildfire virus since he was exposed to the virus while in the womb of his mother, who died and turned while pregnant with him. A fetus is protected from infection in several different ways, the placenta acts as both a barrier and filter to screen out bacteria and viruses. There are powerful maternal antibodies (produced by the mother's immune system) present in both the umbilical cord and in the fetus that fight off infection and pass on some of the mother's innate immunity to the fetus. So it is possible that Laurent could be immune to the virus, his mother's natural defenses could have only allowed a trace amount of the virus into his system, just enough for antibodies to be created for it.

Genet's soldiers are shown using an old naval cannon to fire modern mortar shells by placing the shell in the cannon and lighting a fuse. But that isn't how mortar shells work, the shell has a primer (just like a firearm cartridge) on the bottom and the mortar tube has a firing pin at the base of the tube. The mortar shell is then dropped into the tube and when it lands on the firing pin the primer is set off, thereby igniting the primary propellant. Putting the shell in a cannon and then lighting a fuse wouldn't set it off; although an old cannon could easily be converted to fire a mortar shell (assuming they had similar diameters) by attaching something sharp and pointed to the bottom of the barrel, then all one would need to do is drop the shell down into the cannon, no fuse needed.