Zombie Virus (5e Disease)
From D&D Wiki
Once bitten by an undead carrying the zombie virus, you must make a DC 13 Constitution saving throw or be infected. When infected, you must make a DC 13 Constitution saving throw every hour or take 3 (1d6) necrotic damage. The damage increases by 3 (1d6) for each saving throw you have made against the disease, to a maximum of 24 (7d6). This damage lowers your hit point maximum by an amount equal to the damage taken. If the disease is treated, you will regain your missing hit point maximum, but should your hit point maximum be reduced to 0, you will die and be reanimated as an undead carrying the disease.
Roll a d6 and consult the following table to determine the type of undead: