Plague Doctor Domain

You worship a god who views sickness, healing, and death as stages of life. Everyone gets a cold, and if it's not your duty to your god to give the ill medicine, then it's your duty to make sure the cold turns into a flu.

Bonus Proficiency

When you choose this domain at 1st level, you gain proficiency in the medicine skill.

Rod of Asclepius

Starting at 1st level, you can choose one 1st level healing spell to cast on yourself or others without spending its spell slot. You can do this once per long rest. 

Channel Divinity: Bloodletting

Beginning at 2nd level, the necromancy spells you cast will cause the target to feel sick when you present your holy symbol. The target takes 1d4 necrotic damage after each of their turns until they can make a successful CON saving throw against your spellcasting DC. Every few levels, the damage dealt with the sickness stacks, so 2d4 at 7th level, 3d4 at 11th, 4d4 at 17th.

Emergency Transfusion

Starting at 6h level, you can use your holy magic to perform an act of modern medicine.

Using your medical knowledge and divine magic from your god, you reach out to any downed person within 20 feet of you. Replacing blood lost using healing magic, you stabilize your target so they no longer need to make death saves, and heal them for 2d8 hit points. Casting this also cures any sickness, poison or other maladies such as drunkenness or infection.

Plaguebearer

Starting at level 8, you can siphon away someone's vitality.

You point at a target and mutter a small prayer to your god. After doing so, buboes begin to appear on the target. They temporarily lose 2 CON points, until they are healed by a restoration spell or doctor. If the buboes go unhealed for more than 24 hours, the buboes become necrotic, dealing 1d6 necrotic damage to the target every hour until they are healed by a doctor, amputate the infected area if possible, or die.

Greater Bloodletting

At 17th level, you gain the ability to infuse your weaponised bloodletting with an ill miasma. Once on each of your turns when you hit a creature with a weapon attack, you can cause the target to feel sick, dealing an extra 1d8 necrotic damage to them. Instead of making saves against sickness, they must now make a successful CON save against your spellcasting DC to get rid of the miasma now permeating around them, or suffer 2 points of temporary exhaustion until they can make a successful save. When you reach 20th level, the extra damage increases to 2d8, and 3 points of exhaustion.